# Working with Tesla Packs



## kennybobby (Aug 10, 2012)

Nice looking pack design, thanks for sharing.

Does the aluminum coolant tube that snakes thru the cells have bends and detents for each cell, or is it just a straight run from end to end and relies on the white ribbed material for thermal contact?


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## GoElectric (Nov 15, 2015)

Hi. Of-course I have not taken a module apart, but have seen pictures, and the coolant tube snakes around between the cells - I imagine they press the curves into it before assembly. 

And you are correct about the white ribbed material - it is for heat transfer (somehow).


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## electro wrks (Mar 5, 2012)

GoElectric:

I hope you've read this thread:http://www.diyelectriccar.com/forums/showthread.php?t=175730

What's painfully apparent is that high output battery systems like the Tesla's are potentially more dangerous than other systems. Most failure up to now with less powerful, older battery systems usually involves cells swelling, off-gassing, and not too many fires. As seen in the above thread, the Tesla batteries can burn your house down.

I had a chance to look over a disassembled Tesla battery compartment for its safety features. These include:

1. The modules are isolated from each other by at least two layers of metal with an air gap between the layers of metal.

2. Each module is surrounded in their isolated compartment by a fire resistant material on all sides. It looks like the silicone mica sheets holding the heating elements in hair dryers and toasters. Something like this stuff: http://usamica.com/micapaper/

3. The sealed and isolated compartments that hold each module have vents that apparently pop open in the the event of a fire to direct gases and flames away from the passenger compartment. Here's the patent info on the vents:https://www.google.com/patents/US20120231306

My concern with your battery box design is that it does not have these safety features. It's good that you're using a BMS, unlike the unfortunate, ill advised person in the above thread. My concern is down the line, as the batteries age and/or systems fail, with the potential of a runaway cell(s) and a fire.


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## kennybobby (Aug 10, 2012)

Good points on the safety aspects although it will be difficult and expensive to replicate the engineering that went into the tesla pack design--that's why they cost so much.

Looks like the cooling tube does have bends to contact each cell from the patent images.


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## GoElectric (Nov 15, 2015)

Hi. I agree with Kenny - these features are excellent, but I don't know how to duplicate them (yet). Will ponder venting - burst valves come to mind. 

I did not know that thread existed, so read it all now with interest. But I got a matter-of-fact email directly from StealthE including pictures, and they were chilling. He of-course was supporting my use of an Orion.

I have 1/2" between modules and will use the mica-like material between batteries, and then ceramic wool, which will help. And a BMS. The Orion has some great features which probably would have prevented this fire, like it will shut-down the system if cell voltages are too low, too high or differ by a user-defined amount. It also reduces/ceases charge/discharge currents at extremes of temperature according to a user defined scale.

Mis-handling is a definite issue/possibility as these bricks are not easy to manipulate.

I was not planning on using all of the thermistors, but will re-consider now. 

It is of-course worth noting that EVWest does not use a BMS with any of their Telsa pack conversions. I put down their success to professional work and all-round solid design.

I have had thought of rigging-up a CO2 fire-extinguisher so it floods the battery compartment/box in case of a runaway - not sure why this product does not exist yet, but perhaps its time has come with Tesla cells likely to be more and more in use.

I wonder about regulations - in the face of over-regulation, perhaps it would be a good thing nonetheless. Lars: how are the EU regs??

Thanks for the input/warnings: well-meant and well-received.


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## electro wrks (Mar 5, 2012)

It looks like EVWest is a resident of the Jack Rickard fool's paradise of anti-BMS people. They don't even sell a BMS, as far as I can tell. Although, the Enerdel battery packs they sell have a built-in BMS. Go figure. I hope they have good insurance!

I think these are the safety valves: http://files.wizkid057.com/teslapack/update3/2014-09-09 21.21.31.jpg It looks like they just pop into round holes in the bottom, outside edge of the battery box. Also notice the silicone mica sheet in the foreground of the photo. The sheets I saw were lightly held in place with double-sided tape. You might be able to request the mica sheets and valves from module suppliers. I'm guessing they would otherwise just throw them out. The custom battery box with separated modules would be a lot of work-but doable. It probably should be made of metal.


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## Kevin Sharpe (Jul 4, 2011)

electro wrks said:


> It looks like EVWest is a resident of the Jack Rickard fool's paradise of anti-BMS people.


In recent videos Jack has recommended that a BMS is used with the Model S packs and said several times that EVTV hope to reverse engineer the Tesla BMS.

I believe Jack's 'no BMS' policy is battery chemistry dependent (i.e. he would argue that CALB's are more tolerant of abuse than OEM battery's).


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## electro wrks (Mar 5, 2012)

It's good to see Jack has finally got religion on the BMS debate. I think I saw him on a video after the no-BMS battery fire at his shop, mumbling about looking into offering a BMS for sale. I wonder what EVWest's reasoning is?


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## GoElectric (Nov 15, 2015)

Hi. You guys can get all huffy about these guys on somebody-else's thread. 

I'm here to talk about and learn about what I can do something about.


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## SWF (Nov 23, 2007)

Thanks for starting this thread, it will be useful to me to discuss since I am also using the Tesla modules.



GoElectric said:


> I'm going to use two separate loops too - one for front and one for the back, which means quite a 12V current draw, so unless I think of something clever, will need a larger DC-DC converter (more $$$....).


Another option to the 12V smart car heaters that I am considering is to use the HV water heaters that are normally used for interior space heating. It would likely need some form of thermostatic control to heat the water to the appropriate temperature to heat the modules.



GoElectric said:


> One idea I'd like some feedback on is to keep all of the batteries at the same temperature by circulating fluid through them slowly.


Not sure what you intend with slow fluid circulation. This may cause temperature gradients as you are increasing or decreasing the temperature of the modules, whereas a high fluid flow would minimize the temperature differences within and between modules.



GoElectric said:


> We have a nice design for the battery boxes going. After building the front box out of metal using rails to support, we got the idea to use slots for the back - in 1/2" PVC. This is nice material to work with, as holes are easy to make, it takes a thread very well or you can use inserts if more strength is needed. We cut slots for the battery rails using a table-saw, and joining pieces was quite easy by cutting slots and using 1/8 x 1/2" aluminum bar (see sketch). All is tied-together with plastic banding - metal would be better, but the tooling is about $1,500 and that kind of strength is not needed. Then it sits in a steel frame. We built a box for three bricks, which weighs 37lbs and cost about $150. Half that price was the 1/2" clear acrylic top. If you screw something up, you only need to re-make that piece, not scrap the whole box. I'll attach some pics.


I will be using all metal components in my battery box. I don't have a final design, but the exterior will have three layers: 18 or 20ga steel, 1/2" aluminum waferboard, and ceramic fiberboard all bonded together. Each module will be supported by rails and separated by ceramic fiberboard.



GoElectric said:


> It would be nice to share ideas on cooling/heating, bulkhead connections (BMS anyone?) and...?


I likely will be using the ZEVA BMS but have not ruled out the Orion.


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## electro wrks (Mar 5, 2012)

GoElectric said:


> Hi. You guys can get all huffy about these guys on somebody-else's thread.
> 
> I'm here to talk about and learn about what I can do something about.



Fair enough! I think SWF's design with metal, fire resistant componants, and separated modules is a safe way to go. If anything can be learned from StealthE's experience, it's that some kind of pop-off valves or blow-out bulkheads (or maybe a plenum or ductwork) that direct hot gases and flames away from the passenger area would be a real safety benefit. Separated modules might have also limited the fire. As it was, he had no chance of backing or pushing his vehicle out of his garage because of the location and intensity of the flames.

In a driving situation, all you're doing with these safety features is buying some time to safely park and exit the vehicle.


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## GoElectric (Nov 15, 2015)

Hi, SWF, 

There is some info on using water heater elements on here, and maybe users can pipe-in and update us. In my mind, I just thought it was simpler to buy something designed for the task - the "build or buy" dilemma - and these heaters are a good price. I have a 750W 110V circulation heater which I was going to use for a single-loop design. It was at least designed for automotive use, but running pack voltage (120VDC) through it would have generated water well over 50C, and the high temperature shut-off is close to boiling-point (if it works at all), so that was worrying me. 

I will be trying the Smart Car heater on the bench and hopefully the temps will not get too high as they were designed for these cells, otherwise I don't know what I will do. 

I'm not an expert in reliability! I suggest the Orion though, as it does have temperature-sensing, and can limit current if the temp is too high or too low (eventually to zero if you set it that way). If you can control the temp, agreed, that is important, but a back-up is important too. I like the Orion for this, and other features, but the temperature-dependent output has only one thermistor input, is designed for cooling, not heating, and will require some screwing-around. A GEVCU is another option, but not plug-and-play, to say the least. 

(BTW, I had an engineer calculate 5 modules would need about 900W to heat 5 modules by 10 degrees in 10 minutes. Heating protocol is a discussion which could be had)

On that note, as far as circulating fluid goes, the idea is to reduce temperature-differential between the cells - no heating - so the temperatures would equalize, and cells deteriorate equally over the long-term.

I suggest ceramic wool instead of fibreboard, as it will insulate as well as provide fire-proofing. 

I have a metal box in the front which I built before the plastic idea came-about. I'd like to see pictures of your's, and I can post mine, but unfortunately, it will basically just be a metal box with not a lot of insulation or fire-proofing. This is why I think the CO2 fire-extinguisher flooding the box would be a good idea, but I haven't gone that far yet. 

Electro Works: as far as venting gasses goes, if I decide I need to deal with that, I think the CO2 extinguisher with a manual as well as an automatic release would mitigate long enough to get out of the car. As far as I know, he just had his sitting in the back of an SUV. Figuring-out a system of valves and isolation is beyond me. Glad to have your input though and let's move-forward.

Aside from box construction and placement, another thing to learn from StealthE's failure is to have proper automated safety-protocols in place for these batteries, even though it will cost $$$ and time. This does not mean a cheap BMS which would work 'well' for LiPO4s, and imho does not mean top-balancing. 

I like the theory that StealthE he had one or more cells short-circuit somehow; that seems to fit what we know about what happened. We will never know, but I think the root-cause of this failure is likely mis-handling, which can happen to any of us, or perhaps component failure. A discussion on bench-testing these modules would be a valuable one too.

All the best.


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## Moltenmetal (Mar 20, 2014)

You've made the right decision- a BMS is minimally necessary safety equipment for a Li-ion pack, especially a Tesla pack with its high energy density chemistry.

Strongly recommending minimally necessary safety equipment is not" getting huffy"- it's merely providing responsible advice.

As to your pack enclosure and heating/cooling design, it seems reasonable to me. 

I wouldn't try to provide explosion venting personally- I would provide an open vent in the safest location possible. Want an explosion vent? Tinfoil comes to mind... Lining the interior of the box with something like 1/4" ceramic fibre paper might give the box a bit longer survival time during a fire, directing the flames where you want for a while longer. CO2 will put a fire out, but once the cells are venting electrolyte it is probably not going to prevent a re-ignition- if you can't provide flood cooling, temporary fire suppression may allow enough electrolyte vapour to accumulate that re-ignition will be more violent when it happens than if you just let it burn, but that's a guess. The key is to not start the fire in the first place. For a pack made of cells with metal outer cans, to me that means providing good mechanical support, over current protection, a nonconductive durable inner surface, and a BMS with tested interlocks.


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## GoElectric (Nov 15, 2015)

"The key is to not start the fire in the first place." 

And the rest sounds good to me too. No hard feelings about rants/strong opinions. 

Now, the devil is in the detail. I think there at least 3 more conversations worth having, although the heating stuff is limited to us Northerners:

1) Heating system hardware and protocol - when to heat, and related issues such as controlling charger;
2) Bench testing batteries
3) BMS. 


All the parts are getting close to the battery box, and then I will be doing some bench-testing.


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## Kevin Sharpe (Jul 4, 2011)

Here's what Jack had to say recently about using oem BMS (start at 2:05:06);






You might also find Ed Clausen's BMS issues interesting (start at 1:08);


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## GoElectric (Nov 15, 2015)

Hi. I know this is not my forum, but since I started this thread, I would like to keep the BMS debate out of it. Not that it isn't relevant, but the issue has been discussed elsewhere, and new information would be more valuable if it was added to those threads. I know it is tempting. I even let slip the word(s) top-balancing myself, and was pleased it did not elicit a debate on that particular topic.

That-said, if you are using Tesla modules, as part of the overall discussion I think it would be worthwhile to hear which side of the debate you stand on, and what you plan to do about it. 

I myself am using the Orion. I mostly have the Orion to get a feel for how the cells operate for future projects. A simpler BMS might suffice. It does have the features mentioned previously for temperature-dependant operation, but these could better be managed with something like a GEVCU. 

Right now I have no urgent need to get into BMS operation. What are you working on, or thinking-about?


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## Moltenmetal (Mar 20, 2014)

GoElectric: do the Tesla modules contain any intumescent goo (caulking) between the cells themselves? I thought I read about their use of intumescent materials which are an effective way to reduce fire spread, but I don't recall where in specific it is being used.

If you want to force heat transfer to/from the liquid in the tube, gooing up the gap between cells shouldn't hurt and might help.

Personally I've only seen the intumescent materials as a spray or a caulking- imagine it could be provided in a trowelable consistency material too. But if it were available in sheets, it might be an effective part of an anti-firespread design, helping to reduce the risk of a fire in one module spreading to its neighbours.


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## Kevin Sharpe (Jul 4, 2011)

GoElectric said:


> I would like to keep the BMS debate out of it.


Ok, I'll finish by saying I think Jack's reversal from anti- to pro-BMS (for OEM based packs) is extremely relevant when "working with Tesla packs" 

It's also worth remembering that Jack kindly demonstrated what happens if you ignore 'battery management'


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## oudevolvo (Mar 10, 2015)

As Jim mentioned I am also seriously considering using Tesla modules for my Volvo Amazon wagon (thanks Jim for the inspiration by the way).
I've done quite some research and am convinced I can do it in a safe enough way so I've nearly decided.
In terms of regulations (what you asked for earlier in a post). There are a lot of rules in general. Some info in English can be found here http://rebbl.com/approval-homologation/ and in the more info links.
There is noting specific about what cells you can or can't use. However the fact that there is no documentation or support from Tesla can be a challenge. I'm expecting to cope with this my using a robust design and implementation with a nice look and feel. What supports this is that the Tesla Smart EV modules are also feasible in terms of using them and having a DIY vehicle registered successfully.
My insights so far (and thanks again for the input in my cooling topic):

I will be using the Lithium Balance BMS. Not only to be able to monitor the individual 3.6V parallel strings on voltage, but also for full thermal management (2 taps per module plus on the BMS modules themselves (1 per module).
The BMS will help me in keeping the voltages and temperatures within certain bandwidths and both signal and intervene during both charge and discharge extremes
_Sorry for touching the BMS topic but it felt relevant (won't elaborate on why Lithium Balance)_
Next to the BMS I will also implement active cooling and heating of the modules. Active in this case is without AC but with radiator+fan. Heating is done both by 220V heating elements while plugged in and by using heat from the motor circuit while driving.
My battery boxes will be made out of metal. Thanks to this post earlier in the topic by electro wrks I am also keen on trying to implement the vent valves and will add silicone mica sheets and will also try to implement individual compartments for the modules within my battery boxes while keeping it workable to install and connect them. At least every module will be mounted itself like Jim does
To be continued
More to discover and to learn... 

One question (at this point, probably many more) to GoElectric/Jim:
You mentioned something about CO2 to flood the battery boxes. What I've read on Lithium Ion fires so far is that the most effective way to stop the fire is to take the heat out. In that way the exothermic (runaway) chemical reaction stops (if you cool enough if you still can) and there will be no further propagation. What is the cooling capacity of CO2 while expanding?


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## Kevin Sharpe (Jul 4, 2011)

oudevolvo said:


> What I've read on Lithium Ion fires so far is that the most effective way to stop the fire is to take the heat out. In that way the exothermic (runaway) chemical reaction stops (if you cool enough if you still can) and there will be no further propagation. What is the cooling capacity of CO2 while expanding?


I do not believe any transportable extinguisher will help in something as large as a fire in a traction battery. In the UK the fire service is instructed to allow electric cars to burn themselves out whenever possible (and that's despite them having access to thousands of gallons of water and fire suppressants).

I recommend reviewing the FAA guidance on laptop battery fires to better understand what we are up against;






In the lab it might be worth considering a purpose built extinguisher (see link below for specialist product from EVTV) but the best precaution IMO is keeping packs mobile so they can be moved into the open air at the first sign of trouble.

http://store.evtv.me/proddetail.php?prod=firebane&cat=23

afaik no OEM packs have fire extinguishers, they all use BMS to prevent fires in the first place


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## SWF (Nov 23, 2007)

Kevin Sharpe said:


> I do not believe any transportable extinguisher will help in something as large as a fire in a traction battery.


I would tend to agree. At one point I was thinking of building some form of active fire suppression into the battery enclosures, but decided it was not realistic. The cells are so closely packed in these modules that if a cell fire were to start inside a battery enclosure it would be nearly impossible to stop. That is why I think it is better to build the enclosures to slow a fire from spreading from one module to another, and vent gasses and fire outside the vehicle. This would allow you more time to exit the vehicle and/or move the car to a safe location to burn.

As already discussed, using a BMS with temperature sensors that shut down charging/discharging once a temperature threshold is reached is a good way to reduce the chance for a fire. These tesla modules only have 2 thermistors that are located on two cells close to the inlet and outlet of the fluid loop, so I am considering additional thermistors located within the enclosure.


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## electro wrks (Mar 5, 2012)

GoElectric:

It looks like your thread has been semi-hijacked with this important safety discussion. I just completely read through the patent info on Tesla's battery safety venting system: https://www.google.com/patents/US20120231306 . Talk about a tale of potential doom and gloom! And this is their own battery system!

Because of the increased hazard with using the Tesla batteries, and others like them, I think it's important to have this discussion in the DIY community.

When we tried to express our safety concerns with StealthE before his Tesla battery fire, he pretty much ignored us. Even his Tesla module supplier pleaded with him to be safe, and use a BMS-which he ignored. You, at least, are responding and thinking about the concerns. Thank you.


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## GoElectric (Nov 15, 2015)

Good stuff, especially the video. 

I like the idea of picking-up on the "intumescent goo." Any leads would be appreciated. I haven't disassembled a pack, but yeah, it is in there somewhere. The Tesla packs come with a layer of 1/2" ceramic insulation, so anyone who purchases modules should ask for some, as well as the mica (I have both) and the valves.

More research would be necessary to assess the heat-sinking capacity of a CO2 extinguisher vs. potential heat released in the event of "rapid disassembly (an anachronism I ran-across for batteries exploding). Getting the stuff around the modules would be another challenge. 

Anyone want to start a business building Tesla battery boxes? There is a lot to it, what with heating/cooling and BMS wiring. I'd be willing to build boxes - I have a good (cheap, light, fast to make) design with plastic, am building my own high-current bulkhead terminals and have a design for a 3-D printed manifold which is inexpensive and economical with space. In my design, each box has its own self-contained heating system. I also know someone who is building a wireless BMS which could go in there(!), but cannot say more.

I think most of us are believers in a BMS, so let's just leave it at that. What kind of BMS etc... is absolutely fair-game!


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## GoElectric (Nov 15, 2015)

At Lars' request, I did the calculations for temperature change of a single module charging at 3 amps/cell for 15 minutes. I used the number quoted on his thread of 0.83J/gK. 

Given a pack weighs 45 lbs (I've never weighed one, but 45 is the number I usually see), the temperature increase was almost exactly 5 degrees C!

This is assuming even distribution of heat, no losses, constant resistance with temperature, no other significant resistances, and neglects any part of that 45lbs which is not a lithium cell. There may be other errors but as stated, I'd be pretty certain that number is accurate to +/-20%. 

CONCLUSION: Charging a 12S37P Tesla pack at 100 amps fo 15 minutes should present no heating issues.


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## GoElectric (Nov 15, 2015)

I looked-up the heat of sublimation and specific heat of CO2. Discharging 2kg (5lbs) of CO2 into a box and then converting most of it to a gas would take about 1.1MJ of heat. Assuming most of the solid CO2 stays in the box, this would cool a 3-module pack by about 22 degrees C, or 40F. 

Thinking about the effect of a blast from a fire extinguisher on those cells in the video, this seems at least promising in terms of slowing down a fire. Plus getting rid of any oxygen should prevent it re-igniting for awhile. 

How 'fun' would experimenting with this be???


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## piotrsko (Dec 9, 2007)

The issue would be getting all that cooling inside the cell where the reaction is occuring. Flooding with LN2 might be interesting


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## GoElectric (Nov 15, 2015)

Hahahahaahah.

I think the CO2 would work if the manifold was designed to shoot it in-between the modules, don't you? 

I don't imagine I will do it, but I actually posted this idea in the Spring. There was someone who designed a simple set-up some years ago, but it never caught-on with the DIY crowd. 

Anyway, let's not get too far off topic.


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## Karter2 (Nov 17, 2011)

GoElectric said:


> I looked-up the heat of sublimation and specific heat of CO2. Discharging 2kg (5lbs) of CO2 into a box and then converting most of it to a gas would take about 1.1MJ of heat. Assuming most of the solid CO2 stays in the box, this would cool a 3-module pack by about 22 degrees C, or 40F.
> ??


How would you store 2 kg of dry ice until it was needed in the pack ?.?


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## GoElectric (Nov 15, 2015)

Fire extinguisher!

It is -15C here today, so that would help too....


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## GoElectric (Nov 15, 2015)

I'll throw out what I have done so far to test my packs.

I measured all voltages/cell. I have an RC balance charger from Progressive, so it can display all cell voltages at once. All were within 0.02V. I then bulk-charged them (no balancing) and when they reached 4.1V all were still within the same range. I then discharged them to 3V (still monitoring the voltage) and they were still the same. Then charged them all again and as they were still within 0.02V I concluded there were no damaged cells within the 74P groups since they charged evenly, and that all of the groups were still matched. 

There was a bit of bounce after charging, but did not quantify it.

That was a far as I got. Not sure yet what else to do.

I used a giant resistor wire in a ceramic jig from an electric fireplace to discharge them, tapping it at different places to get a healthy current but not melt my wires too badly.


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## electro wrks (Mar 5, 2012)

Good job. The only thing else I can think of is using thermal imaging to check for hot spots that might be a problem or potential problem cells.


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## GoElectric (Nov 15, 2015)

Hahahaha, too funny, I just bought a FLIR last week, and realised it is not only good for spotting bad connections, but bad cells as well. 

(everybody wants to borrow my FLIR actually - like a new set of eyes)


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## GoElectric (Nov 15, 2015)

Someone wrote to ask how I was able to infer information about individual cells in a 74 or 37P group. I thought I would post my reasoning here for posterity...

The key to how I can say there are no damaged cells is that all six groups charged at the same rate with no balancing. Especially at over 4 volts, any mis-match in capacity between groups would have become evident. From this I can INFER all of the groups have the same number of functioning cells, and as a group at least, are matched. 

To dig down a bit deeper, if the voltage of one group rose more quickly, that would be because it had a lower capacity. On a larger scale, if you charge - say - a 100Ah cell and a 160Ah cell, the smaller one would reach its max voltage more quickly - and reach its minimum voltage more quickly too. I watched particular cell-groups which were the highest/lowest, and they stayed in the same order. Since this crossover did not happen either, I am certain each group has an equal number of cells; it is unlikely all are missing one, two, etc.... 

Edit: hmmmm, I like that - the "crossover" may be a great way to pick up on cells/groups with lower capacity.


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## GoElectric (Nov 15, 2015)

I'm posting a link here to a discussion which arose in the Classifieds section on a thermograph (?) of Tesla modules which seems to show them self-discharging/balancing after being removed from the car. Some discussion ensued regarding whether the Tesla modules balance themselves independent of the Master, or what was going on there.

http://www.diyelectriccar.com/forums/showthread.php/tesla-model-s-battery-modules-24v-165425p3.html

Let's keep this discussion going. 

I have 10 modules, but they do not have boards on them, so I cannot verify any behavior. But even if they could, it seems odd to me they would be balancing themselves out of the car, does it not? One would expect they would only do this when charging. Might storage affect voltage to the point where they try to balance themselves out?? 

The final post on the thread above is useful - it seems to indicate the balance boards do not require a wake-up or some such thing from the Master.


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## oudevolvo (Mar 10, 2015)

@Jim: a question about your batterybox design. 
From the cross-section drawing I tend to conclude that the length of your batterybox is 27.25 inch (69 cm), which is the same as the length of the battery modules.
How are you going to connect/route the cables?
My idea is to connect the modules in series within the box and have only two cables coming out. However I am trying to get an idea about how much space I need to take into account for that.


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## oudevolvo (Mar 10, 2015)

And another question: how do you position the front box in the vehicle?


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## GoElectric (Nov 15, 2015)

Hi Lars,

Nice to hear from you. Since we are doing the same vehicle, these questions are very important, not so-much for others, so I will send you an email.

Jim


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## electro wrks (Mar 5, 2012)

oudevolvo said:


> @Jim: a question about your batterybox design.
> From the cross-section drawing I tend to conclude that the length of your batterybox is 27.25 inch (69 cm), which is the same as the length of the battery modules.
> How are you going to connect/route the cables?
> My idea is to connect the modules in series within the box and have only two cables coming out. However I am trying to get an idea about how much space I need to take into account for that.


These modules can be potentially very dangerous. Have you read over and considered the Tesla battery box design information discussed in posts 4, 6 and others in this thread? The modules may work fine initially. But, as they age or if they're damaged, Tesla's safety features will limit the hazard and damage if there's a fire.


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## GoElectric (Nov 15, 2015)

Yes, you have had your say and been listened-to, no?. The main issue is having a well-managed pack, mainly a good BMS!


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## electro wrks (Mar 5, 2012)

GoElectric said:


> Yes, you have had your say and been listened-to, no?. The main issue is having a well-managed pack, mainly a good BMS!


 One could only hope you're right. But, if this was all that was necessary, you have to ask yourself: Why would Tesla go to all this trouble with the modules? This includes:

1. The modules are isolated from each other by at least two layers of metal with an air gap between the layers of metal.

2. Each module is surrounded in their isolated compartment by a fire resistant material on all sides. It looks like the silicone mica sheets holding the heating elements in hair dryers and toasters. Something like this stuff: http://usamica.com/micapaper/

3. The sealed and isolated compartments that hold each module have vents that apparently pop open in the the event of a fire to direct gases and flames away from the passenger compartment. Here's the patent info on the vents:https://www.google.com/patents/US20120231306

These modules have much more potentially dangerous cells than previously used cells. I have not seen any other OEM go to this level of hazard protection with their cells. I believe if these modules are to be used safely, an equal or better level of protection should be used by the DIY community. Rather than stick our heads in the sand here folks, let's come up with some workable solutions!


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## nucleus (May 18, 2012)

Jack covers it some in the latest EVTV episode.

https://www.youtube.com/watch?v=bUWwZme4DIc


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## GoElectric (Nov 15, 2015)

Yes, I know all of these things and they have been discussed. I'll look at Jack's video, but Electro Works - give a guy some credit and please do not repeat things on my thread unless you have something new to add.


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## GoElectric (Nov 15, 2015)

Anyone hacked a Tesla pump yet??


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## SWF (Nov 23, 2007)

GoElectric said:


> I'll throw out what I have done so far to test my packs.
> 
> I measured all voltages/cell. I have an RC balance charger from Progressive, so it can display all cell voltages at once. All were within 0.02V. I then bulk-charged them (no balancing) and when they reached 4.1V all were still within the same range. I then discharged them to 3V (still monitoring the voltage) and they were still the same. Then charged them all again and as they were still within 0.02V I concluded there were no damaged cells within the 74P groups since they charged evenly, and that all of the groups were still matched.
> 
> ...


Hi GoElectric. Is the 3 - 4.1V range what you are planning to use for a LV and HV cutoff for the charger and BMS? It will still be a while before I set these parameters, but I have read that Tesla uses a HV cutoff of 4.15V which is about 95% SOC. However, charging only to 90% SOC (~4.05V) apparently will extend battery life.


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## Tomdb (Jan 28, 2013)

Anyone got measurements off the thermistors on the tesla pack?

Working on getting some reverse engineering done and any input could be helpful


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## GoElectric (Nov 15, 2015)

Hi. Those numbers are conservative ones, but yes, or even more-so, as the range I will have is about 100 miles, but likely will only drive 10 or 20 miles a day. In general, the higher/lower the batteries go, the harder it is on them. 

Another thing which can contribute to cell degradation is temperature (and time). I will not be cooling the batteries, as it never gets very hot up here and I won't be pushing them in terms of current draw, but I will be heating them. Since I have a fluid loop, I will be slowly running the fluid through them at ambient temperature whenever the car is moving. This is to keep all batteries at the same temperature so they at least degrade EVENLY. Also, I will reverse the flow on the loop every year, so the hot and cool ends get reversed to even-out differences there (I have found the pump I plan to use, which is good for 50,000 hours). I consider this a prudent way to keep them in balance, and my BMS will monitor cell voltage differences just to be sure.

When you charge the cells you will see just how little time it takes to get from 4.1 to 4.2V. Same for 2.5 to 3.0 That-said, I will be able to plug into the BMS and change the HVC and LVC for longer range if I think it is necessary. Much as Tesla does. I think this is a good compromise.


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## oudevolvo (Mar 10, 2015)

Tomdb said:


> Anyone got measurements off the thermistors on the tesla pack?
> 
> Working on getting some reverse engineering done and any input could be helpful


Only info I have found on these so far is by WK057 in 
https://teslamotorsclub.com/tmc/posts/1149103/


> The modules DO have two temperature sensors each. One is on a cell close to the inlet of the cooling loop, and the other is on a cell close to the outlet of the cooling loop. So, the temperature data is available to the car at least, and I'm going to use these sensors in my custom BMS (they're just 10k thermistors).


and in https://teslamotorsclub.com/tmc/posts/1398042/


> temps in C. Temps are probably off, since I haven't done a calibration of one of Tesla's thermistors to see what the appropriate β coefficient is for them. I just guesstimated around 3.9k with a 25C center at 10kΩ for now.


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## GoElectric (Nov 15, 2015)

Yup. We did a couple of measurements, but have gone to the data sheets. Both values agree pretty well, but we are about to calibrate, so if you can wait awhile it would be better, okay? 

What are you working on?


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## Tomdb (Jan 28, 2013)

Ran across the 10K value too. Can someone tell me the pin out of the thermistor connector.

Working on getting a bms slave talking sense. Got a master and slave communicating now just need to get all the probable faults resolved with hardware. in order to get the slave to boot into its "normal" mode.


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## SWF (Nov 23, 2007)

GoElectric said:


> I will not be cooling the batteries, as it never gets very hot up here and I won't be pushing them in terms of current draw, but I will be heating them. Since I have a fluid loop, I will be slowly running the fluid through them at ambient temperature whenever the car is moving. This is to keep all batteries at the same temperature so they at least degrade EVENLY. Also, I will reverse the flow on the loop every year, so the hot and cool ends get reversed to even-out differences there


Based on your description, it sounds like you are planning to plumb the modules in series with respect to fluid flow. I am still trying to decide if I will plumb the modules off a header coolant circuit, so that each module receives the same temperature coolant like Tesla has them in their enclosure, or if I will just plumb them in series. Like you, I don't expect to require much if any cooling. I also don't plan to require much heating, since the car will not be driven in winter. So I am leaning towards just plumbing them in series and running the flow continuously. I will have 10 modules in two separate enclosures, so the longest fluid loop would be through 5 modules in series.


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## kennybobby (Aug 10, 2012)

Gen 2 board with respect to the temperature sensors.

J6 is the sensor jack on the board. Pin 1 is to the left when looking into the 4-pin male receptacle (pin1 is 'up' closest to the black 10-terminal J1 communications daisy connector).

pins wire color
1 ts1+ blue
2 ts2+ yellow
3 ts1- blue
4 ts2- yellow


The Gen 1 board that i have is (possibly mis-) labelled

1 ts1+
2 ts2+
3 ts2-
4 ts1-

although the temperature sensor pair that i got with it is wired exactly like the Gen2. The silkscreen labels are missing on the Gen 2, maybe removed due to the typo on the Gen1 boards?


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## GoElectric (Nov 15, 2015)

Hi. We calibrated our tesla thermistor and it was bang-on! [email protected], 1/Beta=3380.

SWF, I am heating the batteries in parallel, three per box, two boxes, each with a separate temperature control system (working!).

We found our paltry 240W (12V) did not have much effect: about 0.1degrees celcius per minute. 

We also have both Tesla boards and are hoping to harness them. Jack has figured some things out for the slave board, are you aware of this info?


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## SWF (Nov 23, 2007)

Here is a cross-post link where I have described the construction of the enclosures I will be building for the telsa modules. Thought it would be useful to add to this thread.


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## GoElectric (Nov 15, 2015)

Hi Stuart - thanks!

I like the 3-layer shell. Can you say a bit more about the aluminum honeycomb material?

This is quite similar to the front box in my build - I'll be interested to hear how it goes. One thing I'll mention is the wiring: Imagine flipping over alternate modules. Then you have + and - facing one-another and wiring is much simplified. This changes channel spacing (and hole placement) too, but nothing major. 

You may be better at some things, but fabrication presented some issues - as you think things through, feel free to post your questions/solutions. 

There are up and down sides to everything. I have a two-piece metal box in the front and a plastic one in the back - it would be good to discuss. 

Insulation (thermal) is something I'd like to do a better job of next time.


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## boekel (Nov 10, 2010)

GoElectric said:


> This is quite similar to the front box in my build - I'll be interested to hear how it goes. One thing I'll mention is the wiring: Imagine flipping over alternate modules. Then you have + and - facing one-another and wiring is much simplified. This changes channel spacing (and hole placement) too, but nothing major.


I don't think flipping every other module is a good thing:


Half of the bus wires will be short, and you will have less room to move a module during wiring / mounting.
The + and - from two modules will be close to each-other (with an isolation shelve in between this won't matter btw)
depending on box design difficult access to bolts.

If you can use a 'flat' box, one of the best options might be to use part of the original Tesla box... You can easily cut them to the size you need, and you can re-use part of the original busbars:


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## GoElectric (Nov 15, 2015)

Re-using is good!

Points-taken. It has introduced a lot of complexity, for sure.


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## kennybobby (Aug 10, 2012)

ckidder sent me a copy of the cell board binary and i'm helping to disassemble that into the 8051 opcode source. This is for the chip between the cell monitoring chip and the daisy chain communication port. It appears to just be passing data thru, haven't discovered any secret commands of interest as yet...

edit: did find that the boards are uniquely coded with the information on the white QR label, e.g. model and serial number, at memory location x1D02.
And there is a tesla number, "T14C0618393" at x1D38, which may be their part number for the firmware load..?


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## Kevin Sharpe (Jul 4, 2011)

"shorting 70D pack"


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## kennybobby (Aug 10, 2012)

Drunk Idiot with medical insurance! What a stupid thing to do... Hot molten metal in the eyeball would be the first place trophy for such a fool.


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## Coulomb (Apr 22, 2009)

Tomdb said:


> Working on getting a bms slave talking sense. Got a master and slave communicating now just need to get all the probable faults resolved with hardware. in order to get the slave to boot into its "normal" mode.


Forgive me, I'm just skimming this thread to see if it's appropriate to talk about the Tesla BMS firmware. Are the master and slave you refer to above Tesla master and slave BMS boards?

I have worked on TCCH/Elcon charger firmware (pre-2013 models), which use the same processor instruction set (basically Intel 8051 from the 1980s), and found a firmware file. I've had a go at disassembling it with Ida Pro. Disassembling firmware seems to be something few on here are familiar with, so I thought I might be able to offer some assistance if there is interest. I don't have a Tesla battery available, although I could probably get my hands on one for the occasional test if necessary.

It's been hard going so far, but these things often take time. Unfortunately I have quite a number of other projects going, so I can't invest much time right now. So I'm just looking for the level of interest at this stage.

It seems to me that the Tesla BMS is a quite well engineered product, but there is no information on how to talk to it, or how the modules talk to each other. It would be a shame if people had to throw away these BMS boards because there is no information on how to use them, and then have to adapt some other BMS and make all the connections.


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## Tomdb (Jan 28, 2013)

https://hackaday.io/project/10098-model-s-bms-hacking


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## Kevin Sharpe (Jul 4, 2011)

Has anyone produced 3D CAD models for the Tesla battery modules? If not, would solidworks models be helpful?


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## Tomdb (Jan 28, 2013)

I currently have a module, however it is a lot easier just to have a simple block model. As i currently have, how ever without the side fins or the cooling inlets.

Thinking of knocking one up tonight.


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## Kevin Sharpe (Jul 4, 2011)

Tomdb said:


> Thinking of knocking one up tonight.


Great! Let me know if this is something you can share with the community


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## Tomdb (Jan 28, 2013)

Made a nice simple module for packaging.

Main dimensions are accurate, so size of module, location of side ridges and connections.


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## Tomdb (Jan 28, 2013)

Made a simple drawing to show the basic dimensions.


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## Kevin Sharpe (Jul 4, 2011)

Tomdb said:


> Made a nice simple module for packaging.
> 
> Main dimensions are accurate, so size of module, location of side ridges and connections.


Great! Are you releasing these for community use? If yes, where?


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## Tomdb (Jan 28, 2013)

in the zip i have a step file.


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## Kevin Sharpe (Jul 4, 2011)

Tomdb said:


> in the zip i have a step file.


yeh, sorry, missed that


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## oudevolvo (Mar 10, 2015)

I took similar measurements from my modules as far as these are the same. I have modified units to 12s37p so mine are a little higher.

In terms of width, this is 280 mm (or 279.80 mm actually, but I am using 280 as well). How tight would you fit these?
I am creating mounting rails to slide the modules using a distance of this 280mm.


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## Tomdb (Jan 28, 2013)

I would create alot more meat under those rail supports you have drawn, do not forget these things weigh 25kg.

Photo by Boekel shows roughly 28.5mm, if you can create clamps to secure the battery in the sliding direction (forward and back) as tesla do it in their packs.

Measured with my large calipers, the pinch ribs are 28.1mm so I would try and get the distance between rails to make 28.2-.5mm.

Also I would strongly advise anyone stacking them not to stack packs on one another as the do not have the "strong" plastic that makes up the frame protecting the bus bars.


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## oudevolvo (Mar 10, 2015)

Tomdb said:


> I would create alot more meat under those rail supports you have drawn, do not forget these things weigh 25kg.
> 
> Measured with my large calipers, the pinch ribs are 28.1mm so I would try and get the distance between rails to make 28.2-.5mm.


Thanks! 28.2mm sounds like a good idea.
Yes, good point, my box used to be less wide but I increased it in order to create room for the wiring. The support rails definitely need to become bigger.
Furthermore I will add micanite in between the modules. Have even considered (and am still considering) metal separation sheets.
I agree on not stacking them, each module should be supported and hanging on its own. Especially in my case with the studs to hook up the BMS wires sticking out.


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## GoElectric (Nov 15, 2015)

Hi. We are on our second box now, a couple of thoughts:

We have a Solidworks model - I can share files, but won't post them directly on the website.

The spacing between sides we have found works best is 11.25 inches, which is 285.75mm. That leaves a little room for the plastic cover

The modules are alternately spaced vertically 1/2" and 1/4" apart. The former to allow room for connecting between the alternate modules which are facing one-another. The slot-width has been an issue: we now have a digital read-out on our table-saw and have made the slots (in multiple passes) to within 0.005". Also, believe it or not, the rails on either side of the modules are not the same thickness - beware.

We are making the box sides out of 1/2" PVC, and cutting 1/4" (deep) slots. The PVC has ample strength to hold-up the modules, and when the whole things is together (some parts glued, some bolted), it is rock-solid. 

We love these boxes - no metal, cut threads with a drill-tap, easy to cut, glue, etc.... Our 5 module box is built; mounting contactors, shunt, fuse etc... all inside as well.

Edit: still experimenting with a few things bye-the way. Check-out the bulkhead terminals we built:


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## Tomdb (Jan 28, 2013)

Please post some pictures of your boxes for inspiration.


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## oudevolvo (Mar 10, 2015)

GoElectric said:


> Also, believe it or not, the rails on either side of the modules are not the same thickness - beware.


Thanks! Would have missed that otherwise. Just measured and you are right, one rails is 2,97 mm and the other is 2,91.
I was about to use 3,0 mm on each side.



GoElectric said:


> The spacing between sides we have found works best is 11.25 inches, which is 285.75mm. That leaves a little room for the plastic cover


How do you "lock" the remaining 5 mm since the module itself is 279,80 / 280 mm wide. Is my understanding correct that in your case the module fixed and prevented from moving sideways by the 1/4" saw depth?
So the mounting fins of the module go all the way into this depth (and even leaving some room right, since the fin width is bigger dan this 1/4".

Looking forward to a photo and/or screenshot of you model!


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## GoElectric (Nov 15, 2015)

Hi. Sure, will-do. Love to work with people and share ideas.

Here is an early version of a 3-box. Then there is the cooling manifold we had 3D printed. Spent tooooo long on that little project to give away the design, but we could make and ship them to those interested! 

Interested in making double-voltage packs.....

Jim

Oops, took those right off my phone and they seem to upside-down. I'll see if I can re-post.


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## GoElectric (Nov 15, 2015)

Hmmmm, are they upside-down for you? The originals were correct.


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## Kevin Sharpe (Jul 4, 2011)

GoElectric said:


> We are making the box sides out of 1/2" PVC, and cutting 1/4" (deep) slots. The PVC has ample strength to hold-up the modules, and when the whole things is together (some parts glued, some bolted), it is rock-solid.


The designs look great 

Have you put any thought into how PVC will react in a fire? I've been amazed at how much effort Tesla put into the battery box designs and have been trying to replicate most of the features but it eats real-estate and adds a lot of weight.


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## GoElectric (Nov 15, 2015)

Hi Lars. Yes there is very little wiggle-room, and with the weight of the batteries, friction and all that, I never thought about it, but I suppose they have 1mm each way they will move. End-wise, there are various ways of stopping the modules from sliding in and out.


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## GoElectric (Nov 15, 2015)

Kevin Sharpe said:


> The designs look great
> 
> Have you put any thought into how PVC will react in a fire? I've been amazed at how much effort Tesla put into the battery box designs and have been trying to replicate most of the features but it eats real-estate and adds a lot of weight.


Hi Kevin - with a good BMS a fire should only happen if there was an accident, and I figure at that point, nothing is certain. Someone-else kind-of had his say on the issue earlier on in the thread, and I'm just not willing to put in that kind of effort for a one in a million chance. 

But if you have some simple suggestion, I'm interested. I did some calculations on dumping 5 lbs of CO2 into the pack via some triggering mechanism - it would suck out a lot of heat. I think the main thing is to contain the fire, not put it out though. Do you have much info on car fires - how they happen, what the result is, etc...?

Jim


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## AEM (Sep 12, 2014)

GoElectric said:


> Hi. We are on our second box now, a couple of thoughts:
> 
> We have a Solidworks model - I can share files, but won't post them directly on the website.
> 
> ...


About how much weight do the battery boxes add to the Modules and how much does it cost per module to make them?


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## GoElectric (Nov 15, 2015)

Hi. I don't know the exact weight, but the 5-pack box weighs about 40 pounds.


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## GoElectric (Nov 15, 2015)

Oh - cost. For the 5 pack, I think the plastic was around $CAN200, but it could be less. That is for 5 sides, the top will be 1/8" Lexan (clear plastic).

The box is 33" long x 18 7/8 high x 12.25 wide. It will all fit behind the back seat of a 58 VW. That's 27kWh - should have well over 100 miles range.

Oh - I should say "fits" as there will be some modifications of the back seat required where it sits against the top front edge of the box.

Jim


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## electro wrks (Mar 5, 2012)

GoElectric said:


> Hi Kevin - with a good BMS a fire should only happen if there was an accident, and I figure at that point, nothing is certain. Someone-else kind-of had his say on the issue earlier on in the thread, and I'm just not willing to put in that kind of effort for a one in a million chance.
> 
> But if you have some simple suggestion, I'm interested. I did some calculations on dumping 5 lbs of CO2 into the pack via some triggering mechanism - it would suck out a lot of heat. I think the main thing is to contain the fire, not put it out though. Do you have much info on car fires - how they happen, what the result is, etc...?
> 
> Jim


Unfortunately I think you will "kind-of" wish you would have listened to us if your car crashes with people left unconscious, a fire runs through the stacked-close-together modules without separators, and the fire is poorly contained and directed in a flammable PVC and lexan battery box. The consequences of a fire with these modules are potentially so dire, you have to have a back-up safety protocol if the temp sensors, BMS's, HVCO's, LVCO's, -whatever-, alphabet soup of electronic controls fail. I know this, Kevin knows this, FCOL Tesla knows it.

The best designer I've worked with weren't the best because they only came up with great designs. They were the best because they were flexible enough to change their designs when better ideas or safety issues came up.

I think you should at least put the modules in a well secured, metal box with some way of directing hot gases and flames to the outside of the vehicle, if there is some kind of fire.


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## GoElectric (Nov 15, 2015)

Hi Kevin,

Thanks, you have had your say. I appreciate you concern and especially your efforts. Tesla has done an exceptional job and we can all learn from their Engineers.


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## Kevin Sharpe (Jul 4, 2011)

GoElectric said:


> Someone-else kind-of had his say on the issue earlier on in the thread, and I'm just not willing to put in that kind of effort for a one in a million chance.


I'm not sure which country you are based in and therefore I can't really comment on the specifics of your battery box design in relation to local laws. What I can say about the UK is that a DIY builder is undoubtably liable for any damage or injury resulting from vehicle modification and that's why I will do my best to replicate Tesla's battery box features. I know it makes the design complex, heavy, and costly but I'm assuming the Tesla engineers went to this much effort for a reason.

This thread is about "working with Tesla packs" so I hope you understand why people are concerned. That said, I wish you the best of luck with your design efforts


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## GoElectric (Nov 15, 2015)

On another thread there is some discussion about the Tesla Pyro-fuses. Rather than hijack that thread, I thought I post some additional thoughts: 

I've been staring at the big fuses in my battery packs and thinking how nearly useless the second one is. I've changed from one 5-pack to two packs, and now two fuses I guess. One yes, in case of - well, all kinds of things. But what do people think: are two fuses needed with two boxes? About all I can think of is that if the two HV lines between the boxes are shorted, one fuse would not cut the current from both boxes. If I ran the HV cables from the front on opposite sides of the tunnel, that would make such a situation much less likely. If there was an accident, the inertia switch would open the contactors, so there is that too.

The thing is, I don't think the fuse will blow right away anyway. One is a necessary (compromised) solution, and the second one is so close to unnecessary, I'm a bit resistant to putting it in.

Looking for a better solution and this cool Tesla fuse got me thinking. Anything-else out there??


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## Kevin Sharpe (Jul 4, 2011)

GoElectric said:


> I've been staring at the big fuses in my battery packs and thinking how nearly useless the second one is. I've changed from one 5-pack to two packs, and now two fuses I guess. One yes, in case of - well, all kinds of things. But what do people think: are two fuses needed with two boxes?


I hate repeating myself but if you would just add your location to your profile it would help greatly... in the UK you must have fuses per pack... consult with Mike at Indra if you need specifics 



Kevin Sharpe said:


> I'm not sure which country you are based in and therefore I can't really comment on the specifics of your battery box design in relation to local laws.


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## GoElectric (Nov 15, 2015)

Hi, done.

Who is Mike??

Jim


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## Tomdb (Jan 28, 2013)

Always fuse per pack.

I have the rule, as soon as HV goes out of a sealed enclose it needs to have a switch (mechanical or contactor) and a fuse on one of the leads.

you would not want to be hooking up a "HV" pack/module with live connections ever. (some exemptions can be had but i prefer to make the high current connections when there is absolutely no way of shorting something out outside the pack.


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## Kevin Sharpe (Jul 4, 2011)

GoElectric said:


> Hi, done.


Thankyou 



GoElectric said:


> Who is Mike??


'skooler' (profile) I suspect his legal advice would be UK centric so probably worth seeking out someone who understands the local requirements.


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## oudevolvo (Mar 10, 2015)

A while ago I was wondering about that too Jim. See http://www.diyelectriccar.com/forums/#/topics/187657
There you will also find my schematics and indeed, the BMS can (in that way) deactivate both boxes but still I choose (so far) to use two fuses.

My open question related to this is: is for example the A50QS400 fast enough to protect the individual cell fuses?


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## GoElectric (Nov 15, 2015)

I don't really understand your second-last sentence. My contactors and fuse are inside the box - If the contactors are open, then I'm not hooking-up a live pack??

Regardless, any suggestions for fuses? I don't think the one (or two) I have are going to blow fast enough to protect much, except maybe stop something from melting-down after the initial explosion. 

(and just to be clear, that* second *fuse would only be required if there was a short between the two cables? Any other short would be taken care of by the other fuse, as the boxes are in series. Are we talking about an accident, or maybe during assembly, or?? I just can't imagine when that second fuse would be needed, except in a major crash. anyway, with a dead short, all of the internal fuses in the modules would blow?)

I'm playing a bit of the Devil's Advocate here - 'best' way to test an 
assumption is to argue against it. The truth is, I mostly just don't like those fuses - back to why Tesla invented better ones....

Thanks. Will post more pics of boxes soon.

Jim


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## oudevolvo (Mar 10, 2015)

GoElectric said:


> that* second *fuse would only be required if there was a short between the two cables?


Yes, I understand. 
It depends a bit on the type of car and the routing of your cables.
But if you (like me) route the cables on the opposite sides of a tunnel in a RWD car there might be a risk.
What if the driveshaft or it's bearing breaks and start flying around (a shaft that snaps/twists while a car is running) and it hits the cables?
The inertia switch will not do anything about it and the BMS probably won't notice in time either. 
Then a second fuse can add value.

But... in case these fuses are not fast enough they might not even blow before all the individual Tesla cell fuses have blown, right?


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## GoElectric (Nov 15, 2015)

Yup. And thanks for chiming-in. Or I guess the inertia switch could fail to do its job.... Not so easy to test where it should go (?!!).

When I restored the Volvo, I used to tell myself every time a new thing was required (it was inevitably 500 dollars) "Its Art." In this case, it's a living "breathing" battery we are talking-about, and I guess the mantra should be "better safe than sorry." Gotta draw the line somewhere, or I would never step out of my house, but yeah. Will order another fuse of some kind.

Can you post a link to your car (again) - I'd like to see how you are going.

Jim


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## oudevolvo (Mar 10, 2015)

Yes, one fuse more probably disappears in the overall budget.
But still the question is, it is really protecting something?
I want it to protect the cell fuses as well so I don't have to buy new modules.
But if these go first, then I guess the big fuse won't blow anymore so why then add it in the first place?
Can speed be a reason for the new Tesla fuse? To protect the individual cell fuses? (Just guessing, do not know anything about these pyrofuses)

Thanks for asking: this is my English blog:
https://www.oudevolvo.nl/english/

I'm in the middle of designing the battery boxes and have just decided not to use a heat exchanger but I still need to translate that blogpost into English.
Will update my build topic soon again as well.


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## Duncan (Dec 8, 2008)

Hi oudevolvo
A standard fuse will NOT protect anything - everything else will be toast long before it blows


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## kennybobby (Aug 10, 2012)

The individual cell fuses were tested by that whizkid Jason, and they could carry 25 Amps but blew at 26--another amazing tesla feat using 0.011" diameter aluminum wire.

The purpose of external fuses is to protect your external wiring from melting and shorting out the pack, not to save the cell fuses. There should be some control system monitoring the pack current and limiting it well before the cells and cell fuses are in danger, either from overcurrent or high temperatures.

Tesla went to the so-called smart pyro fuse in order to push the current up for ludicrous mode, 1520 Amps for a brief (~7s) period. The previous fuse was marked as 690 or 700 Amps, and looking at the datasheet it could carry 1500 A for ~20-30 seconds. But pushing the margins to the edge of datasheet overcurrent curves is not wise--so they designed their own device with an integrated current sensor to allow the higher currents without nuisance blows due to variations and tolerances in the standard fuses. 

So in your case, you know the size of your pack and from that you can calculate the maximum current before the cell wires fuse. Hopefully your pack monitor or BMS has setpoints and limits below that point for pack charging and discharging currents. Also your motor controller would have current limits. Your external wiring would then be sized to carry the pack and motor currents with some margin factor, and that wire gauge would then be used to pick the fuse(s) to protect each branch of the wiring in the event of a controller fault or inverter or motor winding short-circuit.

i've seen classifieds on the tesla motors club forum selling the pyrofuses for $120.


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## SWF (Nov 23, 2007)

GoElectric said:


> On another thread there is some discussion about the Tesla Pyro-fuses. Rather than hijack that thread, I thought I post some additional thoughts:
> 
> I've been staring at the big fuses in my battery packs and thinking how nearly useless the second one is. I've changed from one 5-pack to two packs, and now two fuses I guess. One yes, in case of - well, all kinds of things. But what do people think: are two fuses needed with two boxes? About all I can think of is that if the two HV lines between the boxes are shorted, one fuse would not cut the current from both boxes. If I ran the HV cables from the front on opposite sides of the tunnel, that would make such a situation much less likely. If there was an accident, the inertia switch would open the contactors, so there is that too.
> 
> ...


I will have two battery enclosures with 5 Tesla modules each and went through the same thought process with respect to fusing. I decided to have a fuse and contactor in each enclosure. Contactors will only be active when the car is being driven or the batteries are charging.


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## GoElectric (Nov 15, 2015)

Hey Kennybobby, nice post.

"The purpose of external fuses is to protect your external wiring from melting and shorting out the pack, not to save the cell fuses. There should be some control system monitoring the pack current and limiting it well before the cells and cell fuses are in danger, either from overcurrent or high temperatures."

I think what we are talking about then is a back-up for the BMS over-current shutdown, right? It may not be a dead-short, and therefore not blow cell-level fuses, but you are right: an inverter failure might make a pretty-good mess, and may take out the BMS with it.

A single fuse would solve that problem, but I guess it makes sense that a non-dead-short could happen somehow which a single fuse wouldn't catch. 

I would like to find one of those pyrofuses from a Tesla - can you suggest a few links? Maybe the set-point can be adjusted. This would be a nice side-line for those wrecking Teslas: sell them pre-adjusted, or with instructions on how to do-so.


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## oudevolvo (Mar 10, 2015)

Thanks @kennybobby for your contribution and helicopter view.
You are completely right, for normal and expected operations my BMS will be in charge and protect the installation by monitoring max current out.

Like @SWF I will also have a contactor and fuse in each enclosure.

Nice to know that the cell fuses are capable of handling 25A. In my case (12s37p) that will be 925A and my normal peak will be around 300A. So I do feel comfortable having my BMS and two times a A50SQ400 in place.


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## GoElectric (Nov 15, 2015)

Okay, I think we can all agree everything should have a backup failure-wise. A fuse is a back up for a failed inertia switch and other things, like a welded contactor. _It would be interesting to have a truth-table with all of the components in it and how each is protected from the failure of another, (internally and externally)._ A suitable fuse between all components is a good method of protection, and that includes a somewhat unsuitable (slow), but still potentially useful big honking fuse in each battery box. 

BTW, are you guys saying you only have a single contactor in each box? We use two. Tesla has contactors on both terminals of its packs, and we just adopted it without argument.

Jim


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## boekel (Nov 10, 2010)

High voltage: two contactors.

For a household battery on a boat (24 or 48 volts) I was considering using only a fuse on the output, but a contactor to create a short circuit when cell voltages go outside spec.
This way there isn't a constant current draw on a contactor, and in normal circumstances all connected devices would listen to the bms or not operate above and below set voltages...

A pyrofuse would be able to get the same result, but with a bang just in the fuse and not on all connected devices...


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## SWF (Nov 23, 2007)

GoElectric said:


> BTW, are you guys saying you only have a single contactor in each box? We use two. Tesla has contactors on both terminals of its packs, and we just adopted it without argument.
> 
> Jim


I was planning to use just a single contactor per enclosure. I assume two contactors are used to provide backup in case one contactor fails to open? I am trying to understand other failures that would be protected with two contactors. I don't recall seeing any other builds or circuit diagrams that have a contactor on both terminals of a pack.


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## oudevolvo (Mar 10, 2015)

Same here, I will also use one main contactor per enclosure.
More contactors is also more contacts so possible points of failure / resistance. So my aim is to use as less contactors as safely possible. Therefore I add the main + and precharge contactor to the rear box and the main - and charger relay to the front box. In that way I don’t need a midpack contactor.
Indeed curious why you have chosen 2 per exclosure Jim.

Furthermore I am interested to hear why you will use the EVTV main BMS board instead of the Orion setup.


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## kennybobby (Aug 10, 2012)

Here's a description from the Miev manual on HV control using + and - contactors, and precharge contactor.

When the electric motor switch is turned to the START position or when the charger is connected, the EV-ECU enters the high voltage start mode. At this time, the main contactor (-) is turned ON, and the charging contactor is turned ON. Then, the smoothing condenser is charged while the current is being restricted by the resistance. Subsequently, when the smoothing condenser voltage exceeds a predetermined value, the main contactor (+) turns ON, and the charging contactor turns OFF. Under the above condition, the main battery becomes ready for use. When in the high voltage termination mode, the main contactor (+) turns OFF, then MCU is instructed via CAN communication to discharge the smoothing condenser. Subsequently, when the smoothing condenser voltage becomes less than the predetermined value, the main contactor (-) turns OFF.


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## Duncan (Dec 8, 2008)

oudevolvo said:


> Same here, I will also use one main contactor per enclosure.
> More contactors is also more contacts so possible points of failure / resistance. So my aim is to use as less contactors as safely possible. Therefore I add the main + and precharge contactor to the rear box and the main - and charger relay to the front box. In that way I don’t need a midpack contactor.
> Indeed curious why you have chosen 2 per exclosure Jim.
> 
> Furthermore I am interested to hear why you will use the EVTV main BMS board instead of the Orion setup.


The legal requirement here (NZ) is a contactor in both legs - I suspect that it is the same in other countries


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## GoElectric (Nov 15, 2015)

I think I will start by saying one can go overboard on safety - one might never get the car built. 

I don't know The Answer to using two contactors per box but yes, in our case it is in case one contactor fails. It is not that expensive or time-consuming. It would be ideal to have some way of determining the actual state of a contactor, but you would still need two: if a contactor does not open, you need to have another one which does.... EVTV sells contactors with a status output and uses them in their Tesla battery BMS. This output feeds back to the ECU (which presumably checks them) and Jack uses two. 

In my case, the Curtis controller does its own pre-charge. I can see if the pre-charge (or lack thereof) caused some failure which fused the positive contactor, two contactors would be good. Jack does not monitor precharge per se - the second contactor closes after a predetermined time, regardless of the outcome of the pre-charge. We don't like this - it seems reckless (and he will probably change this). Also, I believe it is Zeva which makes a pre-charge device with closed-loop feedback, which I would use if the Controller did not do-so itself. Not sure what voltages it is rated for.

Further to the topic of battery isolation and safety, we are thinking about having an illuminated manual switch on the box which opens the circuit to the contactors. And/or a light which turns on/off on the outside of the box whenever the terminals are live (or not); this would be helpful when handling the box,and again, simple to do. One of those plasma bulbs (?) which you find in testing equipment. 

In general, I think something rigorous to keep track of protection would be useful, but rules of thumb honed by experience are good too. I've been scratching some things down and perhaps a truth table is too complicated. Perhaps one table for each component, or failure-mode? This may go nowhere, but if there is a reliability engineer out there somewhere, I'd bet he has a rigorous method of tracking protection from cascading failures.

You really need to read-up on Jack's Tesla battery BMS, but at the very least, we prefer to have the cell-taps terminate inside the modules themselves, with voltages and temperatures reported by isolated CAN, rather than running 7 tiny little wires per module (ready to vapourize if they are shorted) some distance to the Orion. The Orion has features Jack does not have in his software, so in the end it is what you are comfortable with. Heck, what can I say: I'm an early-adopter.


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## SWF (Nov 23, 2007)

GoElectric said:


> I think I will start by saying one can go overboard on safety - one might never get the car built.
> 
> I don't know The Answer to using two contactors per box but yes, in our case it is in case one contactor fails. It is not that expensive or time-consuming. It would be ideal to have some way of determining the actual state of a contactor, but you would still need two: if a contactor does not open, you need to have another one which does.... EVTV sells contactors with a status output and uses them in their Tesla battery BMS. This output feeds back to the ECU (which presumably checks them) and Jack uses two.
> 
> ...


I guess I will rethink the option of using one or two contactors per enclosure. Safety is top of the priorities list, so even if it also introduces another failure point I will have to consider it.

The controller I am using (Soliton 1) has built in precharging, but the chargers (Brusa 513) will require precharging since I don't plan to have the chargers permanently connected to the battery. So I will need to work up the proper control of the contactors/precharging for charging vs driving.

With respect to BMS, I agonized over using the Orion vs distributed ZEVA BMS setup and decided on the ZEVA. The Orion had greater flexibility with respect to programming, but I did not like the idea of running cell tap wires all the way to the Orion, since at least one battery enclosure would be some distance to the Orion. Also, the Orion is not a sealed unit, so would either need to be put in one of the battery enclosures, put in its own enclosure, or put in the passenger compartment. None of these were ideal for my build. Folks that are not in a hurry will also have the option of the Lithiumate Vinci EV BMS which is supposed to be available sometime next year. It is a distributed BMS system that would probably also work well with the Tesla modules.


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## Solarsail (Jul 22, 2017)

Terrific project, GoElectric. Just a quickie - for safety reasons such as containing a fire, would a metal box not be necessary? A rack made out of two metal plates and also sheet metal between the modules?

Also, where does one get some good PVC sheets? Thanks.


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## Kevin Sharpe (Jul 4, 2011)

Solarsail said:


> for safety reasons such as containing a fire, would a metal box not be necessary?


Many engineers would argue that a 'fire proof' battery box is required, not only for safety reasons but also to protect the engineer from legal liability when something goes wrong. In the UK (and I suspect in many countries) the insurers will undoubtably hold the engineer liable when shit happens 

My advice is to follow the Tesla battery box design as closely as possible. It's fully documented in patents, online posts, and YouTube videos. It will make the design heavier and more expensive but IMO that's the price we pay for using cutting edge technology in our cars. If you're unwilling to do this then I believe you really should use safer cells like those from CALB or Nissan. Note 'safer' not 'safe' as EVTV discovered.

Don't get me wrong, I'm absolutely prepared to fight for the rights to undertake DIY (see here) but good engineers prepare for worst case scenarios


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## SWF (Nov 23, 2007)

Kevin Sharpe said:


> My advice is to follow the Tesla battery box design as closely as possible.


I agree and I am building my enclosures with as much impact and fire protection as possible. The only Tesla design element I was not able to incorporate is the complete physical isolation between the modules in the enclosure.

I will be posting some further details and photos of my enclosures to my build thread in the next few weeks, but here are some of the basic physical design components:
- 12 gauge steel bottoms and 16 gauge steel sides and top
- 1/4" thick Grade 1494 UTR composite lining the inside of the enclosures, providing additional strength, fire resistance, and electrical insulation
- 1/16" thick UTR composite between each battery module

The UTR composite material has the same UL94-V0 flame resistance rating as the silicon infused mica sheets that Tesla uses above and below each of the modules in their enclosure. I originally had planned on a three layer design for my enclosures, but decided to simplify and make use of thicker UTR composite material and a simple steel outer shell. The UTR composite is quite strong since it is a fiberglass composite, so the 1/4" thickness provides quite a bit of additional strength inside the steel shell. It is also flame resistant. I tried burning it with a propane torch (~2000degC), and it does not actually combust, but just slowly degrades. Once the propane flame is turned off, it does not continue burning. See photo below which shows what the material looks like after burning it for about 1 min with a propane torch. Not sure the enclosure would completely contain a battery fire, but it would certainly slow it down enough for a person to get out of the car.


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## GoElectric (Nov 15, 2015)

Hi SolarSail et al. Yes a flame-proof box would be nice. We made one and found lots of reasons to go to plastic, but flame-proofness went with it. One question I would have for the steel box guys is: how do you attach the modules to the rails? We ended-up drill-tapping small holes through both, and this was really tricky. 

I'll attach a few pics taken the other night of the sides of a two-pack. If there was some kind of fireproof material we could use instead.... I suppose one could cut slots in aluminum, although it would be tough, to say nothing of deafening?

I haven't been willing to, but is anyone trying to mount them on their sides?

Sorry, phone not connecting - no pics.


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## GoElectric (Nov 15, 2015)

Oh - I forgot to answer the question about sourcing the plastic. We bought from a local plastics supplier, Industrial Plastics and Paints - no biggie to find something local. I just called and they charge $CAN13/ft2 for 1/2" pvc. For a 5-pack that would be about 6 sq ft. Cheep! A 1/8 clear plastic cover will be about the same/ft2. We put together a 2-pack last night and it weighs about 20 lbs, and will mount it with metal tabs (angle-iron) screwed onto the sides with 1/4"-20tpi bolts, and another brace. The bolts will bend before the plastic gives-way, we tried that last night too....

You need a saw which can make accurate cuts. A DRO (digital read-out) will help a lot. They are easily installed and only a couple hundred bucks. We made one without and wouldn't do it again....


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## Solarsail (Jul 22, 2017)

Heh - a fellow Canuck - am in Vancouver. I am buying new 18650 Panasonic (Sanyo) 'B' cells 3.4Ah (or LG cells) from a reputable supplier to build 12 kWh for a Leaf and maybe 100 kWh for a sailboat. I plan to spotweld 1.5 kWh (sub)modules - 13s10p and make that a building block for the projects. For the larger project I plan to go 8s2p(4p13s10p) (a module is made of 4p 13s10p sub-modules in parallel - 6 kWh - then two modules in parallel to make a bank, and then 8 banks in series). Each 13s10p sub-module comes with one micro-fuse per cell, its own balancer, multi-way protector board, and one CCCV 1 kW step-up charger per module. I don't plan to have an intelligent BMS for the 12 kWh, but will have it for the 100 kWh. Charge/discharge is low-C so no heating/cooling. Of course this is all on paper and in practice it will be very different as I hit the realities. If Tesla T3 2170 modules of 15 kWh each become available, then that would be the way to go. 

I reckon in the marine environment I have the option to detect a thermal condition, via the BMS, and flood the module with a pump and seawater.

What kind of safety boxing would you recommend for each module (1.5 kWh and 6 kWh)? 20 gauge sheet metal, or aluminum or plastic? Multiple layers? Insulation? Big vent or small vent? I don't plan to stack the modules.


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## GoElectric (Nov 15, 2015)

Hi. No offense SS, but you might get a better response on this if you post your own Thread (don't be shy!)


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## Solarsail (Jul 22, 2017)

Thanks Go-Electric. I will wait till I have built a sub-module so I know what I am talking about, and have something to report in the thread. One thing I noticed is that few DIY people build modules from scratch. This is a bit of a mystery for me. The Chinese are just putting e-bike 13s10p 1 kWh modules together (using 2.2 Ah cells) and dumping the market, and they seem to work. How many e-bikes have caught on fire? The hoverboard fires are I believe due to the use of LiPoly, or faulty electronics. Out of millions of hoverboards shipped, many via air, how many have caught fire?


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## Boxster-warp (Jun 22, 2014)

Helle
In Germany the Most People Build a alloy battery Box.
Tesla Moduls, Calb ore Leaf cells, fore all.
Better fore the TÜV.
And alloy Do Not wheigt any more.
Greetings Greenboxster


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## oudevolvo (Mar 10, 2015)

GoElectric said:


> One question I would have for the steel box guys is: how do you attach the modules to the rails?


For my front box I add stops at the end of my rails. I plan to slide the modules in as a tight fit.
Not sure yet how to secure them at the front. Current ideas are a bolt though the alignment hole and/or a stop screw all the way through in front of it or some kind of spanner screw/block.
This is my current design. Am still working on the rails and in doubt whether I will ad steel in between the modules or just micanite. 
@SWF Thanks for your take, I think I'll decide similar.
Currently I anticipate on using 1,5 mm steel for the body of the box. The highlighted part in yellow and that weighs 11 kg excluding front and top cover.


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## SWF (Nov 23, 2007)

GoElectric said:


> One question I would have for the steel box guys is: how do you attach the modules to the rails?


I am using 3/4" aluminum u-channel mounted with the open side down to support each side of the Tesla modules. The 3/4" dimension works well, as this is the dimension that is flat underneath the module rails. The u-channel is bolted to the sides of the enclosure, through both the UTR composite and outer steel shell. The module is then put in place and the module rails are bolted to the u-channel with nuts that are fixed in place up inside the u-channel. The bolts are located at the notches that are along the sides of the module rails, the same way that Tesla bolts the modules in their enclosures. I built special spacers the same thickness of the module rail that allow the bolts to securely hold the module rail to the u-channel. 

I was very careful when mig welding the enclosures together, getting the dimensions exactly right, and the modules fit snugly between the u-channels with basically no gap. Once the module is bolted to the u-channels, they are very secure and cannot move in any direction. Attached below is a photo showing three of the u-channel rails mounted to the inside of one side of the enclosures. For final assembly, each pair of u-channels and module is mounted sequentially starting from the bottom module and then mounting the next set of u-channels and module, etc.


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## oudevolvo (Mar 10, 2015)

I like that idea / approach, thanks!
That triggers an idea I have been playing around with in my head of using the separator sheet as a mount flange.
Something like this.







Have you explored that?


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## SWF (Nov 23, 2007)

oudevolvo said:


> I like that idea / approach, thanks!
> That triggers an idea I have been playing around with in my head of using the separator sheet as a mount flange.
> Have you explored that?


I tried to think of different ways to isolate the modules when they are stacked on top of each other, rather than just a single layer side-by-side like in the Tesla enclosure. Bending an alloy or steel sheet like in your diagram so that it acts as both a separator between modules and as a top clamp for the side rails would provide some separation. I had similar ideas, but I could not think of a way to extend this type of separation all the way past the ends of the module to the sides of the enclosure. At the terminal end there will be the heavy gauge cables connecting the modules and the BMS cell tap wiring, and at the other end there will be the hoses for the cooling/heating system. So these cables and hoses prevent a complete isolation between the modules when they are stacked vertically, unless you somehow have separate compartments for the hoses and wiring. However, I still think having a sheet between the modules like in your diagram would be helpful. I myself decided to just use a 1/16" thick sheet of the fire resistant UTR composite material I described above between each module.


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## GoElectric (Nov 15, 2015)

Nice ideas. I can appreciate the level of accuracy involved in lining-up the modules with the holes in the U-channel. On the box I did build out of steel, we welded angle-iron onto the side, with pre-tapped holes in it match with holes in the flanges. Rather drill our own holes rather than have spacers, but similar. It worked, but there was a lot of checking. To assemble, the angle iron had to be ground-off in places to be able to install the threaded screws. This messy, and your approach of building it up as you go has that advantage.

What is this UTR like? I found this:
https://www.electro-wind.com/500-1-...minate-sheet-130-c-red-48-w-x-96-l-sheet.html

Aad wonder if I could cut slots in it for the batteries?

Jim


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## boekel (Nov 10, 2010)

Some solutions make things very expensive and a lot of work.

Tesla uses a steel lid with an insulation blanket on top (not sure if it's fire retarded btw), and a thick aluminium base (about 1/4"). In case of fire in a module it would not spread quickly, as there are vents in every module bay.

Also there are the mica sheets, these will help slow down the melting of the case, but are probably also used to give some thermal insulation in normal use.

So it would slow down the fire, but not stop it.

I'd say you can use about any material for the pack, preferably one that has minimal toxic gas release in a fire (pvc is not one of them thus). Ad a thin layer of stainless steel to the outside, with a vent (plugged with something to keep the weather out) to a location where fire can do the least damage.

If you use aluminium, please realize this melts at a low temperature and is not a fireproof material. normal steel would also work but stainless steel is much more suitable for high temperatures.

All the fancy expensive materials might slow down the heat transfer, but it has to be able to get out somewhere because pressure inside the pack will rise until something blows.

Probably simplest solution: make a wooden box, 1mm thick stainless steel cover, vent, done.


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## SWF (Nov 23, 2007)

GoElectric said:


> I can appreciate the level of accuracy involved in lining-up the modules with the holes in the U-channel.


It actually was fairly straight forward. A hole drilled right in the center of the 3/4" u channel also lines up perfectly for the depth of the notches in the sides of the module rails. It was also nice that 5/16" nuts fit snug up inside the u channel. See 3 photos below that show the channel held up under the a module rail, one of the spacers I made that have the same thickness as the rail, and a 5/16" locking nut up inside the u channel. Bar stock with matching holes is laid over the rail and then bolted down sandwiching the rail to the u channel.























GoElectric said:


> What is this UTR like? I found this:
> https://www.electro-wind.com/500-1-...minate-sheet-130-c-red-48-w-x-96-l-sheet.html
> 
> Aad wonder if I could cut slots in it for the batteries?
> ...


Yes, that is the material. I ordered from a local supplier. The total cost for all the 1/4" material I used to line the inside of the enclosures plus the 1/16" material for between each module was ~$350, so not too expensive.


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## Solarsail (Jul 22, 2017)

The modules are designed to vent the hot gasses, if the module catches on fire. However, if you put an enclosure around several modules, and stack the modules on top of another as in an oven, would that not cook the modules above and below the fire module? Are you providing vents in the enclosure to vent the gasses and fire? If the enclosure has vents, then would the gasses by any chance pass by other modules to get to that vent?

The module vents allows for the release of the hot gasses. On the other hand, they also allow oxygen to enter and sustain the fire. Would it not be a better idea to have smaller vents or maybe tubed vents so that oxygen cannot enter the enclosure? 

When an 18650 pops with flames (and often they pop without a flame), would it not require oxygen to maintain the fire? So maybe funnel all the hot gasses through a metal tube drain vent to outside, and this will prevent oxygen from getting in?


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## electro wrks (Mar 5, 2012)

Solarsail said:


> The modules are designed to vent the hot gasses, if the module catches on fire. However, if you put an enclosure around several modules, and stack the modules on top of another as in an oven, would that not cook the modules above and below the fire module? Are you providing vents in the enclosure to vent the gasses and fire? If the enclosure has vents, then would the gasses by any chance pass by other modules to get to that vent?
> 
> The module vents allows for the release of the hot gasses. On the other hand, they also allow oxygen to enter and sustain the fire. Would it not be a better idea to have smaller vents or maybe tubed vents so that oxygen cannot enter the enclosure?
> 
> When an 18650 pops with flames (and often they pop without a flame), would it not require oxygen to maintain the fire? So maybe funnel all the hot gasses through a metal tube drain vent to outside, and this will prevent oxygen from getting in?


Well, you've hit the nail on the head, safety wise. Tesla keeps the modules separate, except for the stacked front two. And, all modules are surrounded by silicon mica sheets good for ~ 1000F (540C). BTW this is quite a bit higher than the UTR stuff @270F (135C).

On the venting issue, each module in the Tesla in its separate space(again, except for the front two) has 6 one-way/pop-off valves exiting into a plenum running along or into the rocker panels under the doors. I don't know the exact plumbing here, but it looks like it's designed to direct hot gasses and flames away from the cabin.

If I were buying these modules, I would make sure they came with these valves and the silicon mica sheets. At least this would allow a DIYer to try to replicate the Tesla safety features in a battery box design.


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## SWF (Nov 23, 2007)

Solarsail said:


> The modules are designed to vent the hot gasses, if the module catches on fire. However, if you put an enclosure around several modules, and stack the modules on top of another as in an oven, would that not cook the modules above and below the fire module? Are you providing vents in the enclosure to vent the gasses and fire? If the enclosure has vents, then would the gasses by any chance pass by other modules to get to that vent?
> 
> The module vents allows for the release of the hot gasses. On the other hand, they also allow oxygen to enter and sustain the fire. Would it not be a better idea to have smaller vents or maybe tubed vents so that oxygen cannot enter the enclosure?
> 
> When an 18650 pops with flames (and often they pop without a flame), would it not require oxygen to maintain the fire? So maybe funnel all the hot gasses through a metal tube drain vent to outside, and this will prevent oxygen from getting in?


The modules themselves are not vented, but yes the compartments each module sits in within the Tesla enclosure are vented. My enclosures will also be using the same vents and safety release plugs that Tesla has in their enclosure. However, you are right that arranging the modules stacked is quite different than having them in arranged side by side. If there is ever a fire, I expect all the modules will end up burning, so I am simply trying to design the enclosure to contain it for as long as possible.


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## SWF (Nov 23, 2007)

electro wrks said:


> And, all modules are surrounded by silicon mica sheets good for ~ 1000F (540C). BTW this is quite a bit higher than the UTR stuff @270F (135C).


Yes, the mica sheets have a higher temperature rating, but they both have the same UL94 V0 flamability rating based on my understanding/reading of the silicon mica sheets Tesla uses. Of course I was curious to test this, and the UTR material holds up fairly well to a propane torch (~2000C) (see my earlier post with photo).

The mica sheets in the Tesla enclosures are ~1mm thick I believe, whereas I used 1/4" thickness UTR material to line the interior of my enclosures to increase strength of the enclosure, but also to provide higher duration of fire resistance and decrease thermal transfer.

I don't think there is a way to make a DIY enclosure 100% impact and fireproof, so it is just a matter of building it to the best of your ability using a design that will work for your project. Even the Tesla enclosure is not perfect since in very rare cases there are fires in severe accidents.


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## oudevolvo (Mar 10, 2015)

SWF said:


> I don't think there is a way to make a DIY enclosure 100% impact and fireproof, so it is just a matter of building it to the best of your ability using a design that will work for your project. Even the Tesla enclosure is not perfect since in very rare cases there are fires in severe accidents.


I fully agree! An advantage of DIY in my case is that I do not sit on top of them. The modules will be under the hood and in the spare wheel / fuel tank area. Nevertheless I will also use steel + the vent plugs and a much separation between the modules as possible given the available space (volume+weight).


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## Kevin Sharpe (Jul 4, 2011)

oudevolvo said:


> I will also use steel + the vent plugs and a much separation between the modules as possible given the available space (volume+weight).


That's my plan as well... great to see so many people taking these issues seriously


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## GoElectric (Nov 15, 2015)

We finally glued together our battery boxes this week - meaning we think they are good! Contactors and fuses were mounted and bus bars made-up. Jack's BMS fits inside one box. We just need a couple of amphenol connectors, a push-button illuminated switch and will also install a little plasma/neon bulb across the terminals to give final warning if there is pack voltage across them (contactors welded). 

Somebody asked about the weight of the boxes, and a 2-pack weighs about 15lbs empty. Not including the bracketry to mount it to the car, which is mainly a 34" piece of angle-iron.


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## GoElectric (Nov 15, 2015)

I mentioned awhile ago that the rails on either side of the modules are not the same thickness. The rail on the LHS (facing the terminals) is thicker. Well, it turns-out we have found TWO thicknesses on that side, so beware when cutting your slots (and in general, check your assumptions!).


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## boekel (Nov 10, 2010)

And they can be aluminium or plastic...


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## GoElectric (Nov 15, 2015)

Hah - really, plastic now? Have you got a pic?


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## boekel (Nov 10, 2010)

My 'first' pack, with the rectangle V2 BMS boards

http://boekel.nu/foto/17/2017-01-tesla/index.htm


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## GoElectric (Nov 15, 2015)

Yes, indeed. Right around 108 I can see them. Since we are at it now, are the plastic rails also different thicknesses on either side? Maybe you don't care, but we made our slots JUST wide enough (for what we thought were two different rail thicknesses), and it mattered. 

It looks thicker too.


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## boekel (Nov 10, 2010)

IIRC they are the same (different on each side) thickness as the aluminium ones, @Tomdb has one of the modules, I only have aluminium ones now.

@Oudevolvo has 8 of my 12s converted modules and couls also measure them.

For myself: I put the modules in boats, less trafic bumps...I just make the slot 4mm wide so it always fit's


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## oudevolvo (Mar 10, 2015)

Using a rail that is different in thickness left and right and even on one rail does not make sense to me. Looking at the teardown pictures I'd say they use a n shape to press down the modules. Furthermore the edge on the mounting material for the stacked modules is the same over the whole lenght.
I just measured two of my modules (plastic rail type) and did not find any significant differences within a rail or left versus right.
All within 2,87 and 3,02 mm


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## GoElectric (Nov 15, 2015)

Hi Lars,

Yes, you make some good points. I think we are probably talking about quality control issues, not design. I have not seen a pack come apart myself yet, so was just reporting. 

I like the nice, tight-ish slots, and we are tooled-up to cut exactly what we want, but perhaps for most it is not important. 

I really must post some pics of our 2-pack and 3-pack. I just have to go out and buy a nice LED bezel, then we can wire the whole thing up. Lots of trial and error bending bus-bars - and always room for improvement - but we like them, and like to swap 'n share.


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## oudevolvo (Mar 10, 2015)

Yes, I agree, probably quality control issues. Perhaps that's why they also used metal rails.
I like the tight slots too. My idea is to use a steel frame which supports the modules and build a skin around it.
I used my mill to cut a slot of 3 mm in a 15x15x2 tube.







My idea was to use these on the outside frames and bolt the modules onto the shared center frame.







Nice idea, but in practice it turned out that there is not enough room to tilt it in.







At least not when I want the space between the frames to be max 280mm.
Now I'm switching to a design where I bolt them down on all sides.


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## GoElectric (Nov 15, 2015)

Hi Lars. How about drilling holes through the rails and bolting them to the frame? I did that with one box, you just have to make sure all stays lined-up. I know you want all kinds of layers of insulation etc... in there which I don't use, but I can take some pics.

Here is a pic of a PVC 2-box, ready for final wiring. Contactors and bus bars complete. We made our own terminals which go through the aux panel on the side of the box.


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## oudevolvo (Mar 10, 2015)

Impressive engineering and fabrication Jim!
What kind of copper do you use? (Width and thickness?)

Using the slots I’d hoped to fix the module already in up/down and left/right direction.
In my redesign I indeed bolt them onto the frame at both sides.
Another advantage is that it allows me to center the module between the frames.
Futhermore I decided to use 4 stacked tubes for the middle frame and put long bolts all the way through.


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## GoElectric (Nov 15, 2015)

Hi Lars,

That is 1x1/8 inch copper, plus we have a section of 3/4 x 3/16 which needs to be narrower to go through the current transformer in the front box. I think the former is good for something like 400amps continuous, and the latter a bit more. Overkill for us regardless. We bent it in a 100 ton press - also overkill, but not easy to do by hand. Even with the press, quite difficult to get them just right. 

Pretty nice work yourself, my friend. 

If those batteries are all in series, you should flip alternate ones over, so the pos/neg terminals line-up. You can see what I mean if you look at that pic closely. That changes the spacing for your rails, of-course; hopefully not too late.


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## itchyback (May 28, 2014)

We seem to be all going with similar design ideas.
In Australia the battery boxes have to be made to withstand 10,15 and 20g's of force in the reverse, sideways and forward directions respectively. They also have to be enclosed in a way that you cant touch the terminals.

Here is my design, 2mm aluminium. each box holds four modules, The wires, coolant tubes and BMS wires will pass through end piece. The modules bolt through the lips between each section. Aesthetics were really important to me, i didnt want any bolts visible. They also have to be really small to fit the space, 30cm wide x 72cm long x 32cm high. 

I like the idea of enclosing the contactor in the box but my car doesnt have space for that. I'll have to put it nearby. 

feedback welcome


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## GoElectric (Nov 15, 2015)

Hi ItchyBack,

That is a cool design. Modular. Strong.

Who decides when your box is strong enough??? How? What about brackets - you don't want it to go flying either, hahah.

I see the same thing as with Lars' box: since all of your spacing seems the same, you must be stacking them all the same, whereas flipping alternate ones will give you better terminal alignment, with plus and minus directly above one-another. 

Having the contactor(s) inside the box means when there is no power to them, the box it is touch-safe. We like that a lot (will also have an LED hooked up across the terminals so if somehow there is power, you will see it).

Do post more pics, as I like the simplicity. I'd like to see the end and how it all goes together. 

We might have to go all 3D geometric like Lars sometime, but don't have the Solidworks skill, so it is pretty intimidating.


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## oudevolvo (Mar 10, 2015)

@GoElectric Thanks, that's about 80 and 90 mm2 of copper, very nice.
Originally the Tesla modules are connected with 25x3 semi flexible busbars.
Myself I won't go anywhere near the amps Tesla is pulling out of these things.
In my case it will be about 300A max.
The cable underneath my car will be 35 mm2 and for the busbars I was thinking about 25x2 = 50 mm2 so it can be bended more easily.

@itchyback Nice design and fabrication! What I don't understand yet is how you will fix the modules within these enclosures and how you will connect the components of the casing.

Flipping the modules is an interesting suggestion that crossed my mind earlier as well. However that brings up another topic:
- How do you safely connect all these modules? - 
And with 'connect' I mean the initial installation of them. Especially with 12s modules in series the voltage builds up quickly.
Flipping the modules makes your working area for installing an tightening the bolts even smaller.

My current idea is to weld the frame to the car. Then add the modules one by one and connect them in series. When all wiring and cooling hoses are in place, them mount the battery box skin with bolts to the frame itself and the car as a cover (of course in such way that it is water and air tight). By adding the cover later I have plenty of space around the modules.

In the approach that I have a regular non-flipped orientation I was thinking of using the same 35 mm2 cable as I'll be using underneath the car to connect the modules. I can add the modules sequentially so that will allow me to connect the cables to the module while I can still easily access the bolts.
See attached schematic and order.







In that case however I still have a 'live' wire/lug nut with increasing voltage while adding the next module awaiting to be connected to the next pole.
@Boekel suggested to use single pole Anderson connectors in this case. 
That way you still have a 'live' wire but enclosed by a connector.
Having said that: that approach also opens up the route with flipped modules. I can first bolt the cable with connector onto the module. install it and after all modules are in place connect the connectors.
But on the other side, if I'm not using these nice flat copper busbars then how much trouble is a little longer cable.
At least in my wiring layout I don't think it's an option to use those kind of solid copper busbars. Unless I indeed flip the modules but then I don't see a safe way to secure the bolts (at the right torque).

Looking forward on hearing your input and your approaches of hooking up the modules while in the box.


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## itchyback (May 28, 2014)

GoElectric said:


> Who decides when your box is strong enough??? How? What about brackets - you don't want it to go flying either, hahah.


The weight of the boxes X an acceleration force (10,15 or 20g, specified in the Australian vehicle modification and construction rules) creates a force, Mpa. Using autocad i can stress test the boxes to see what kind of forces are exerted on the boxes, identify weak spots and change the design. The Von Misses Yeild Strength is the amount of force a material can withstand before breaking. for unwelded T6 aluminium, it is 150Mpa. as long as the software does its magic and gives me a number less than 150, its good to go! 
Welding aluminium reduces its strength to like 50Mpa, steel for example is 450Mpa. I really wanted to save weight, so i worked hard to stick with aluminium that i dont have to weld. 
Actually 1.6mm aluminium was technically strong enough but the engineer recommended using 3mm for the base and 2mm for the rest. He said this would make it more durable since its in a moving car and may get hit with a stone. I think this is good advice since over time the material strength will reduce because of shakes and impacts etc.



GoElectric said:


> I see the same thing as with Lars' box: since all of your spacing seems the same, you must be stacking them all the same, whereas flipping alternate ones will give you better terminal alignment, with plus and minus directly above one-another.


Flipping alternate ones would have been a great idea, i wish i had read about this sooner. At this point i have spent $500 testing my design, building a prototype and getting it approved. I think i'll have to stick with it. I had simply planned to build angled metal bar battery straps. slightly more difficult but not a big problem. Electrical cable would fit but i'm trying to save space (12mm vs 3mm width).
I did a few sketches changing my design to be able to flip the batteries, It was actually a few mm taller and each frame was slightly different width which would make manufacture more time consuming and expensive. adding a few mm to a few of the frames you could actually get four frames the same with. space is a premium for me so i'm scrimping for extra mm's!

@Oudevolvo
It will be fiddly. I will stack two frames on top of each other then insert a module into the top frame and bolt through all three. Thus the bolts securing the battery also hold the frames together. Conveniently, if something should impact the bottom frame, i would only need to replace that piece, and could reuse the rest. 

I have not fully solved or comprehended the issue of bolting the battery bars in while the modules are in place. I'm trusting i will find a way. Doing one module at a time would help so stacked modules are not in the way. flexible cable may also help. at this point i am crossing my fingers and hoping its not a problem, i may regret that though 

I would really like to have some form of socket in the wall of the box to attach the cables to, inside the box. then have a plug i can insert into the socket to connect the modules together, i am trying to find something but havent looked thoroughly yet. As i'm using the full tesla pack, i think 400v 1000amp plug and sockets are hard to come by.


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## SWF (Nov 23, 2007)

Hey guys. I am also working through the details of connecting between modules in my enclosures. I will be using a combination of 2/0 cable with crimp lug connectors and flat 1x1/8" copper bar. For the diagonal connections between stacked modules, I will be using the 2/0 cable and have ordered some 90deg elbow lugs. One of my enclosures is tight on space and regular lugs cause the cable to stick out from the end of the modules, but using these elbow lugs for the diagonal connection between modules will be a more effective use of the space.

For those using flat copper bar, you may want to consider tinning the copper surface to reduce corrosion. You can buy tinning solution, or just tin the surface using high tin or lead free solder after appropriate cleaning and flux.

Also probably a good idea to apply conductive anti-seize lubricant on all connections. I have some from EVwest, but standard copper based anti-seize may work as well.

With respect to doing the final connection between modules, probably a good idea to be wearing electrician or lineman gloves for safety.


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## GoElectric (Nov 15, 2015)

Hi Guys - 

Thanks, Itchyback - of course, Solidworks. 

EVTV has some really nice terminal connectors - expensive, but definitely the ticket. We decided our method is okay - have added a protective sheet between the terminals to prevent accidental shorting-out, but as the contactors are inside the box, even shorting them out should (!) not be an issue.

http://store.evtv.me/proddetail.php?prod=rebling7009

Flipping requires 6mm or so more space between alternate modules. We can slide the modules in and out while assembling, so have better access to that tight space, then all can be slid in as a unit and held in place with set screws.

I'm using nordlock washers, which don't need much torque at all, and can actually be done by feel; as the cams slip over each other, there is a kind-of click, and they won't back-off. They are not exactly easy to find, but no secret either.

As far as connecting them together, I see your point, and an Anderson connector might be a nice way to do it, but it just seems to me the main issue is a mistake - if all is done right the bus bars don't carry any current. It is a little nicer when there are no diagonal cables/bus bars floating around too.... I'm getting nervous just thinking about it, but honestly, we have been connecting/disconnecting as part of fitment for weeks and rarely does my spiders-sense tingle, telling me I have to be care-ful. We have the contactors mounted directly to the modules. I can send some pics if anyone has a particular question.

Yes to Wurth or other non-corrosive pastes, and/or tinning, but I don't see why one has to tin the entire bus bar.


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## SWF (Nov 23, 2007)

oudevolvo said:


> @GoElectric Thanks, that's about 80 and 90 mm2 of copper, very nice.
> Originally the Tesla modules are connected with 25x3 semi flexible busbars.
> Myself I won't go anywhere near the amps Tesla is pulling out of these things.
> In my case it will be about 300A max.
> ...



I think there is risk while installing and connecting cells/modules in any kind of EV, so rather than complicate the connection design I would just do this final step as carefully as possible. For the cables going from one module to the next, you could install insulating caps on the cable lugs and then pull them off just before you attach the lug to the next module. So for example, the cables attached to your module #1 would have insulating caps on the free cable ends that you would pull off just before connecting them to the terminals on modules #2 and #3.


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## oudevolvo (Mar 10, 2015)

SWF said:


> I think there is risk while installing and connecting cells/modules in any kind of EV, so rather than complicate the connection design I would just do this final step as carefully as possible. For the cables going from one module to the next, you could install insulating caps on the cable lugs and then pull them off just before you attach the lug to the next module. So for example, the cables attached to your module #1 would have insulating caps on the free cable ends that you would pull off just before connecting them to the terminals on modules #2 and #3.


Thanks @SWF. That's the way I will do it.
I agree, once it's installed it's installed. So I won't be adding the Anderson connectors. Instead I am going to design the battery box in such way that I can install the cover separately.
That allows me to install the modules in the frame and carefully connect them. In that way I have plenty of space to move around. After everything is hooked up I will then close the box by placing the cover from underneath.

Front box approach is a little different since I plan to slide the modules in from the front. Since I stacked them stepwise I can hook them up much easier.


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## GoElectric (Nov 15, 2015)

FYI, I ran across a video last night where someone put a dead short on a Tesla module. There is a pretty big arc, but no flames and all was over in 1/2 second, as all of the cell-level fuses blew. 

One dead module, but at least no explosion(s).


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## itchyback (May 28, 2014)

GoElectric said:


> Hi Guys -
> As far as connecting them together, I see your point, and an Anderson connector might be a nice way to do it, but it just seems to me the main issue is a mistake - if all is done right the bus bars don't carry any current. It is a little nicer when there are no diagonal cables/bus bars floating around too.... I'm getting nervous just thinking about it, but honestly, we have been connecting/disconnecting as part of fitment for weeks and rarely does my spiders-sense tingle, telling me I have to be care-ful. We have the contactors mounted directly to the modules. I can send some pics if anyone has a particular question.


Can i clarify your comment when you said bus bars dont carry any current? I expected if the controller is drawing 1000amps, then the batteries would be pushing it out (through the bus bars)?

I'm asking because i have a 400v system up and the motor will take up to 1000amps. If i can use some form of plug and sockets to join the the battery modules together then that would be great.


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## GoElectric (Nov 15, 2015)

Sorry, badly-worded. There should be no current _when you are connecting them._


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## itchyback (May 28, 2014)

Got it!
I thought that was an option of what you meant, but I just had to check. what seems obvious to me may not necessarily be true, i never trust what i think i know.


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## Kevin Sharpe (Jul 4, 2011)

Chris Hazell has created a 3D Model of the Tesla battery module and posted it on GrabCAD (here)


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## GoElectric (Nov 15, 2015)

Thanks, Kevin.


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## oudevolvo (Mar 10, 2015)

Another question/topic related to Tesla packs.
(How) do you connect the cooling loop?
I know Tesla has all modules in parallel.
Initially this was my plan as well because of the optimal temperature distribution and flow, but I am in doubt now.
This complicates the design of the battery box and increases the number of water connections (and thus the chance of leakage).
Therefore I am exploring the option to hook up the modules in series.
At least within each box (3 front, 5 back) and perhaps even all 8.
Then I do not need a 'distribution block' like this.







It allows me to only have 1 hose in and 1 hose out per box. Disadvantage of course is that the last modules in the chain will be warmer (during use) or cooler (during heating) than the first ones. Other disadvantage is the increased pressure drop. I am planning to do a flow and pressure test for the second aspect.
Looking forward to hearing your thoughts on this.


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## GoElectric (Nov 15, 2015)

Hi Lars. 

We 3D printed a distribution block, but I don't think it will work for you, because your batteries are not stacked directly above one-another?

And there is the problem with leaks. We just have barbed fittings and hose clamps.

If you do the series method, I would just reverse the direction of flow once a year, or something like that. So the batteries will degrade equally....


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## GoElectric (Nov 15, 2015)

With some trepidation, I should probably report here on the Tesla BMS from EVTV - which uses the original boards on each Tesla module. Aside from Jack not shipping a bunch of things (and no packing slip, and refusing to admit it), we have it working now, and no real complaints. His documentation is much appreciated, and the quality (and workmanship) of everything is good.

One feature missing is Charger control - he has only programmed it to work with a solar charger. You may be able to buy a charger control box from Jack for another $200, or program your own Micro to do it. 


It is a little awkward dealing with unused wire length between the connections, but we did not re-make the harness, although we do have to make one to go between the two boxes. 

We bought and installed our own bulkhead connectors (+ pins) in the same series.

The Pre-Charge setup is hokey (not closed-loop, just a timer), so we will not use it. And as far as we can tell, the expensive contactors he uses with the status outputs do not shut-down the system, as it all works without them connected. I haven't tried simulating a welded contact yet - must do that. 

This may not be Jack's problem, but for our system, when we have the USB cable connected to his board(s), and hit the power, all the contactors close with no precharge delay - not sure what that is about.


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## oudevolvo (Mar 10, 2015)

Thanks!
Yes, I remember your manifold, it is beautiful.
But not usable in my case indeed since indeed I do not have all modules stacked directly on top of each other (front 3 staircase, back 3+2).
I already have a source for fabricating a manifold so that is not a problem.

My main concern is indeed leaks. The less connections, the less the chances are it will leak one day (without you knowing it for a while).

So the question is: does the increased complexity (a.o. doubled connections) justify the benefits of a parallel circuit?

Perhaps I can design in such way that I can always install manifolds later on in the same in-out hole in the box if the BMS info reveals the delta T's are too significant between the modules.

Thanks for your update on your progress with the Tesla/EVTV BMS.


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## GoElectric (Nov 15, 2015)

Hi Lars - 

As far as the net effect on the batteries, I think it depends upon how much you will use the heating. If you only heat them below - say - 10C my guess is not a lot, so series should be okay. Because you will have higher pressure, there may be more chance of a leak (albiet less connections) though. Tesla has those nice connectors, but the hoses have to be specially made? 

We think that as long as you use good quality silicone hose, clamps should be just fine - they can be placed behind the tab on the inlets. Just not too tight, as that will damage the hose, so we found the spring-type clamps in the right size and used them. I think they are colour-coded, and we used the green ones.

Thinking about it, I don't feel the problem is really leaks, as long as you don't damage the hose taking it off during testing. They are really tough to get off, and so had to use pliers, which can of course pinch and damage them. We replaced a lot of pieces, and would recommend all new for final assembly, just to be sure. 

So, yeah, go with series, and in the end, it is just one hose in and one hose out either way, so you could go back and make it parallel in the future. Otherwise, I hope you get that swapping the direction of flow will equalize degradation over time, helping them stay in balance.

What are you using for a BMS??


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## GoElectric (Nov 15, 2015)

Putting the hoses on is also tough. Pushing too hard will bend the aluminum conduit, so we placed a block of wood behind, so it didn't move.


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## Kevin Sharpe (Jul 4, 2011)

We're copying Tesla's system as closely as possible with 16mm distribution hoses and 8mm clip on connectors for each battery module. We will parallel all the modules because we don't want to risk the system being compromised by excessive heating of modules in a series connected array.

I'm not sure if anyone has posted the connectors used by Tesla are Push To Lock Quick Connectors ("P2L") made by A Raymond (see here).

We're currently researching sources for the connectors and hoses and will post our results here


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## GoElectric (Nov 15, 2015)

Okay. 

I appreciate your attention to detail, and will look forward to hearing about your progress with the hoses!


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## oudevolvo (Mar 10, 2015)

Great find Kevin! Did not know about the A Raymond source. Would be great if we could have something like that. 
My current approach was to use hoses and connectors like these Dorman 800-116 connectors. https://www.dormanproducts.com/p-27515-800-116.aspx
Looking forward to hearing possibilities on these A Raymond style connections.


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## Tomdb (Jan 28, 2013)

I am using a fuel connector 7.89mm https://www.ebay.co.uk/itm/Connect-37213-Fuel-Line-Straight-Quick-Connector-7-89mm-x-8mm-Pk-3/272861846919


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## Duncan (Dec 8, 2008)

Hi Guys
Re-worries about temperature differentials

How much energy are you talking about? as far as I can see unless you are racing there is not much energy/power involved in cooling/heating your battery - that is once it is at the desired temperature

1 litre per second of water will change temperature by 1 degree C requiring 4.2Kw of heat

So if you are flowing that 1 l/sec and your whole battery is wasting 4.2 Kw of heat while you are charging then the out temperature will be 1 degree warmer than the In temperature

And 4.2Kw is a LOT! - supercharger level!

Then once you have finished charging the energy input will go down to nearly zero and the temperature change across the pack will also go to near zero 

1 litre per second is a decent flow - but even at 1/10th of that I really don't see any problems


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## Kevin Sharpe (Jul 4, 2011)

Duncan said:


> And 4.2Kw is a LOT! - supercharger level!


~67kW for a 16 module pack... more like CHAdeMO on steroids 

We're hoping to exceed these power levels with our open source supercharger development and that's before we factor in the 6.25kWh modules 

The Model S/X includes a chiller and works the cooling hard during charging. I'd hate to see an expensive conversion handicapped by poor cooling design.


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## Kevin Sharpe (Jul 4, 2011)

GoElectric said:


> I appreciate your attention to detail, and will look forward to hearing about your progress with the hoses!





oudevolvo said:


> Looking forward to hearing possibilities on these A Raymond style connections.





Tomdb said:


> I am using a fuel connector 7.89mm


Exciting times


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## oudevolvo (Mar 10, 2015)

Duncan said:


> 1 litre per second is a decent flow - but even at 1/10th of that I really don't see any problems


Good point!
I tried to do some calculations.
I estimated the length of the cooling tube within a module to be 520 cm and assumed the internal diameter is 8 mm.
In my case (8 modules) that is around 4 meters in total if you would put in in series. At 16 ltr/min that would result in a pressure drop of 1,5 bar.
My Pierburg can only deliver a delta P of 0,6 bar so I expect a flow of 0,01 liter/sec.

Using the Joule effect I calculated the delta T for some scenarios.
Average driving, 2 hrs at 14 kW on average = dT of 7 degrees
Fastcharge 20 min at 100 A = dT of 7 degrees as well
Do these numbers make sense or do I need to check my calculations?
So basically nothing to worry about, even without cooling....

I will create a test setup that allows me to measure the pressure for different flows with 8 modules in series. Perhaps that gives a nice balance between flow and pressure.

On the other hand I can really appreciate the approach of Kevin:


> We're copying Tesla's system as closely as possible


So also keen on connecting all modules in parallel while reducing the chances for leaks to a minimum.


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## Kevin Sharpe (Jul 4, 2011)

A useful reminder of what we are dealing with...


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## Duncan (Dec 8, 2008)

Hi Kevin

4.2 Kw in waste heat is a LOT - I would expect the charging process to be 95% + efficient so 4.2 Kw in waste heat would imply a charge rate of over 84 Kw


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## Kevin Sharpe (Jul 4, 2011)

Duncan said:


> 4.2 Kw in waste heat is a LOT - I would expect the charging process to be 95% + efficient so 4.2 Kw in waste heat would imply a charge rate of over 84 Kw


Sure... Jack at EVTV has some interesting test data in his latest video... see 53:19 (battery with cooling) and 2:31:00 (battery without cooling)


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## boekel (Nov 10, 2010)

I also found that charging (and discharging will probably be the same?) even at 0,5C noticeably warms up a module.

While charging other type of lithium modules they only warm up a couple degree's C when charging at 1C

So I think getting the good weight / capacity level of these modules comes at a cost: higher internal resistance. (and being able to connect two packs together without blowing things up)


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## Karter2 (Nov 17, 2011)

Kevin Sharpe said:


> A useful reminder of what we are dealing with...


 Does anybody know more regards that incident ?
It looks suspiciously like the Tesla ran nose first into the temporary concrete barrier...
......another "Autopilot" error ????


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## Duncan (Dec 8, 2008)

Karter2 said:


> Does anybody know more regards that incident ?
> It looks suspiciously like the Tesla ran nose first into the temporary concrete barrier...
> ......another "Autopilot" error ????


Why blame the autopilot? - people have been running into things in MUCH MUCH larger numbers for over 100 years


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## Karter2 (Nov 17, 2011)

It just seemed to have many similar circumstances to this previous one...
So the possibility of a similar cause has to be considered.


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## oudevolvo (Mar 10, 2015)

Today I did some flow / pressure tests with three Tesla modules.
1) Tesla modules hooked up in series
Pierburg pump at 100% duty cycle (full power)
Pressure = 1 bar
Flow = 0,8 litres/min (measured by hand, was 1 litre/min according to flow sensor but needs to be calibrated better)

2) Tesla modules connected in parallel using Tesla’s tubing for the batteries but in my connecting tubes a restriction of even 9 mm.
Pierburg pump at 100% duty cycle (full power)
Pressure = 1 bar
Flow = 6 litres/min (measured by hand, was 12 litre/min according to flow sensor but needs to be calibrated better)









From these results I'm going to proceed connecting the modules in parallel.
Having 5 in series would result in even a smaller flow and with all 8 in series I think there won’t be much flow left.
Another advantage is that you can have a reasonable flow with much less pump power (and thus less Amp. draw).
In my case connecting my front (with 3 modules) and rear (with 5 modules) in series and within the boxes in parallel could be feasible.
But I think I’ll just stick to my original plan to connect everything in parallel.

That does bring us to the question:
How do we design that while finding a balance between aesthetics and robustness/safety?

Most robust solution probably is to position the distribution blocks outside the battery boxes.
However that would mean 6 hoses in/out my front box and 10 in the back.
Advantage is that there are only the 6 / 10 connections onto the modules within the box.
Prettiest solution probably is to install the distribution blocks inside the battery boxes. That means one hose in and one out per box.
As a result I will have 12 / 20 connections within the box.

Using the A. Raymond connectors that Tesla uses which Kevin is after is probably the best option. However I'm afraid the tools to be able to make the crimps will be quite expensive.

After that I think my preference still is to have the distribution blocks within the boxes and have manifolds fabricated out of aluminum.


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## GoElectric (Nov 15, 2015)

Hi Lars - 

Good to know! As you know, we went quite a ways down this rabbit-hole. In the end, we decided to shelve that car and build another one which had no battery heating at all. You might consider no heating, and save yourself a ton of grief. And money.

If you do want to go for it, we found a 3D printing company that offers nylon injection-moulding. I assume they 3D print a positive piece, make a mould out of it, then inject plastic. The price for a 4-module manifold was only about $US100. Since you are already into Solidworks, I would investigate that.

But, what we did decide heating-wise for the next time was to consider using electric heating "blankets" between the modules - very slow response, but sooooo much simpler. Leaf cells are inferior to even this method, after-all.... 
Sad to leave all that great Tesla engineering at the table, but it just seemed unnecessary for a car that will never be driven in the winter anyway. Not sure what kind of use you are planning in your car. The *main* thing is to be able to warm them up before charging. With 8 modules, you should still have decent range when it gets cold - minimum temperature there is....?

Jack at EVTV sells the blankets I was referring to - I think by coincidence they fit almost perfectly on top of the Tesla modules. 

I really must go visit your blog again.....


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## Boxster-warp (Jun 22, 2014)

Hello
Is cooling not more important than heating? Thinking about the safety of tesla cells that can still burn is important for cooling. 
Or am I wrong? 

Greetings Boxster-Warp


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## GoElectric (Nov 15, 2015)

Only if you live somewhere hot, and/or plan on racing the thing. Lithium cells are still quite happy at 50C.


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## oudevolvo (Mar 10, 2015)

In The Netherlands is does not really get colder than -10 during winter.
But I do want to use the car all year. My idea is to also pre-heat the battery while plugged in if I need maximum range for a certain trip.
I wil explore and consider the option to use those heating blankets. Did look into them at the time I still planned to use CALB cells.

And I agree that is is mainly for being able warm them up.
2 hours of continuous average driving or 20 minutes of fast-charge will only result in a temperature increase of about 6 to 7 degrees in my application if my calculations are correct.
So even if it already is 30 degrees outside there won't be a problem.
On the other hand circulating water in between the cells using the Tesla technology will facilitate a more even temperature distribution which of course is beneficial for the lifespan of the pack.


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## GoElectric (Nov 15, 2015)

Good on you, Lars


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## Alaskanviking (Mar 10, 2018)

Hi, I have been reading all the relevant threads and wanted to get some clarification. I am researching using the tesla modules as a 48v or 24v house bank on my boat. Currently I have a 24v system. Space is at a premium.

First regarding the battery box. I was leaning twards a frame of marine ply glassed to the hull. However reading the posts regarding fire, I'm thinking I need a layer of the fire resistant variant of g10 fiberglass plate.

Originally I had planned on just stacking the modules. After reading this thread it seems to be a better idea to bolt aluminum u channel as rails to the sides of the box and then bolt the module to the rail. I don't have a lot of space due to the shape of the hull, but I am hoping to maximize what I have and get 4 modules per box, one on each side of the mast. ~1000th at 48v or 2000ah at 24v. It seems that the keys are to be careful not to damage the fuse wires and to use a bms. Is it possible to stack using a full size g10 plate in between each module?

Next is the BMS. I've been looking at Jacks evtv bms, and it looks promissing, however it doesn't seem very compatible withe my victron gear, nmea 0198, or nmea2k networks. Victron appears to accept a can bus, but it's hard to tell which bms it's compatible with. I like t h email idea of a programmable bms like orion or batrium, but am having a hard time picturing how those would connected to the tesla modules.

Cooling I was thinking on using PEX and PEX manifolds at the end of the module to parallel the water cooling. The manifolds come in stainless or brass. PEX can be heated and softened to push on the tesla coolant nipples, and the PEX crimps should in the art crimp on well. I was planning to get a 5gal marine water heater for the head of the system and rewire it to turn on the heat when it's cold. The engine heat coil inside could be set with a temp managed valve or it can be repurposed for seawater cooling. 

It's a boat so I'm more or less storing energy, and I don't nessesarily want a cooling pump running all the time. When do I run the cooling pump? When it's charging, and high amp discharges? How much power? What about solar panels all day? I am using a victron 240v 5k 48v or 24v inverter charger, which does have programmable relays. Part of my reason for increasing to 48v is the possibility to use larger DC motors vice 120/240v motors that have to go through the inverter . I have a large dive compressor 5hp 240v, a 24v 1800w maxwell windlass, and likely will install a watermaker with a 5-7hp motor. Would I need to run cooling when these large motors are in use?

Thanks

V/r

Robert


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## john61ct (Feb 25, 2017)

I guess you're planning on "self-insuring" your boat? 

For safety I would recommend a purpose-built drop-in system with integrated BMS from Victron or Lithionics/Ocean Planet. 

To DIY for cost reasons, just use large prismatic LFP cells like Winston or CALB.

Big dangerous science projects have no place on a boat.


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## Jimbo69ny (Feb 13, 2018)

I agree with the previous post. Just because you dont have the space is no reason to skimp on safety, ESPECIALLY on a fiberglass boat. You mentioned a wood box and "glass". I assume you meant fiberglass right? You know how flammable resin is right? If you had a cell go thermal, you and your family would be sitting on top of a fire bomb. You have to go with aluminum or steel, preferably steel and have each module isolated from the others.

As for cooling, you need a temperature sensor. Its impossible to say that you only need cooling during charging. It all depends on what temperature they are at. The Tesla modules have built in temperature sensors, use those if you can, add new ones if you cant. Connect that to a pump and keep the cells around 70 degrees. If you do they will last a long time, assuming you never over charge them or completely discharge them. 

I am working on a project myself to add 18650 cells to my car. I am doing everything I can to make them as safe as possible. And thats in a car! In a boat, out on the ocean with your family or friends.... Now thats risk. It can be done but dont cut ANY corners!


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## Alaskanviking (Mar 10, 2018)

john61ct said:


> I guess you're planning on "self-insuring" your boat?
> 
> For safety I would recommend a purpose-built drop-in system with integrated BMS from Victron or Lithionics/Ocean Planet.
> 
> ...


Quite honestly I have to disagree. While I like and wouldn't mind the victron or other lithium brand commercial battery, and the would connect directly to the victron data bus and solve several problems. However they cost over $4k per 24v battery at ~250ah and comparitively take up a lot of space. That means I can't fit as many as I need for the capacity I want.

The LFP cells also take up a lot of space and are just as dangerous as the tesla batteries on a boat, are more difficult to get a hold of, and many of the same issues as the commercial victron batteries. I haven't ruled them out, but at this time their capacity compared to price and volume of space isn't what I am looking for.

Any large capacity battery regardless of their chemistry is dangerous on a boat, including the 24v bank of 4 GC2 6v batteries. Corrosion, salt air, saltwater, moisture, poor connections/crimps, untined/non marine wire ect. Even a regular west marine 12v deep cycle in a 12v system can discharge enough juice to catch fire, or blow up from overcharging. My original charger wasn't even regulated and boiled the old batteries to death. I am well aware of these issues, use ABC standards, aerospace crimpers and the best wire and amp connectors I can get. With regards to electricity on a boat or car or a house the only solution is to do it right. just making it work or cheap cables and connectors is setting anyone up for fire, damage or worse.

Big dangerous science experiments are better on a boat, where you are less likely to injure anyone but yourself, vice a car in public on crouded roads or experimenting with charging in a garage within a crouded residential area. Knowing what your doing, designing in safety, and doing things right eliminate ost of those worries. 

Which is why I asked on this forum, to get more insight into doing things correctly. I just watch evtv where they have a 48v 6 module power wall that would get mounted on a wall vertically. He is simply stacking the modules and securing them with plastic u channel, an aluminum bar and threaded rod. Which isn't what is recommended on this forum but is similar to how most boat batteries are secured. 

Thank you

Robert


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## Kevin Sharpe (Jul 4, 2011)

Alaskanviking said:


> I just watch evtv where they have a 48v 6 module power wall that would get mounted on a wall vertically. He is simply stacking the modules and securing them with plastic u channel, an aluminum bar and threaded rod. Which isn't what is recommended on this forum but is similar to how most boat batteries are secured.


Be careful who's advice you follow 






I think many people on this forum are treading carefully and trying to emulate the OEM's when it comes to battery safety. Obviously, we deviate on occasion because we are not designing vehicles from the ground up. One of the most noticeable progressions is with the BMS where most people are now favouring electronic systems which were routinely called "Battery Murdering Systems" a few short years ago 

Don't take the criticism to heart but rather understand that most people are genuinely concerned about battery fires and the potential impact on the DIY conversion scene.

If you decide to proceed with Tesla modules then I'd suggest you read the Tesla patents and review the teardown videos before copying as much of the Tesla battery design as possible. Then make the assumption that you will have a fire on your boat and ask yourself how you're going to survive that. My suggestion is that you dump the batteries over the side and if that's not possible design a system that can cover the battery box in lots and lots of water


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## Alaskanviking (Mar 10, 2018)

Jimbo69ny said:


> I agree with the previous post. Just because you dont have the space is no reason to skimp on safety, ESPECIALLY on a fiberglass boat. You mentioned a wood box and "glass". I assume you meant fiberglass right? You know how flammable resin is right? If you had a cell go thermal, you and your family would be sitting on top of a fire bomb. You have to go with aluminum or steel, preferably steel and have each module isolated from the others.
> 
> As for cooling, you need a temperature sensor. Its impossible to say that you only need cooling during charging. It all depends on what temperature they are at. The Tesla modules have built in temperature sensors, use those if you can, add new ones if you cant. Connect that to a pump and keep the cells around 70 degrees. If you do they will last a long time, assuming you never over charge them or completely discharge them.
> 
> I am working on a project myself to add 18650 cells to my car. I am doing everything I can to make them as safe as possible. And thats in a car! In a boat, out on the ocean with your family or friends.... Now thats risk. It can be done but dont cut ANY corners!


I was referring to FR-4 fiberglass plate. It's a fire resistant manufactured panel used for high voltage and high temperature applications. Essentially make the structure or base of the box using marine ply, then line it with FR-4 for fire resistance. I have been thinking of aluminum as an alternative, but that also has to be lined with an insulator. The problem with metal is it corrodes and conducts electricity, both a big no-no in the marine environment. Even coated steel wouldnt make it long in the bilge. Aluminum is better but since we're dealing with electricity it has other problems, primarily stray current or salt crystals from dried salt water will eat and corrode aluminum rather quickly. On the plus side aluminum would be easy to make water tight in case of flooding.

I'm leaning more and more twards the evtv bms as it would be able to use the module bms and temp sensors, and it may be possible to build a can translator or gateway device to push the data into the boats data bus, or write code to have the bms out but nmea can natively 

Thank you

V/r

Robert


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## Alaskanviking (Mar 10, 2018)

Kevin Sharpe said:


> Be careful who's advice you follow
> 
> Then make the assumption that you will have a fire on your boat and ask yourself how you're going to survive that. My suggestion is that you dump the batteries over the side and if that's not possible design a system that can cover the battery box in lots and lots of water


That's awesome, not something I've seen yet. I was thinking of plumbing a co2 or fire boy system in already, but I have a high volume salt water deck wash pump close by. It wouldn't take much to plumb in a valve to fill the box in an emergency. Maybe a vent/overboard discharge to keep cool water flowing through. Likely be bad to use a metal box, as the saltwater could short the main terminals putting juice to the box or short the cell fuses.

Thank you

Robert


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## aeroscott (Jan 5, 2008)

I'm putting lithium batteries in a steel 47 ft. sail boat , high pressure dive compressor, large shop compressor 30cfm,32 volt anchor windless, 12 volt,48 volt ups 5kw (cheap runs my welder @ 150 amps).small ups 12 volt for computer etc.
I'm going to build a fire box for the batteries, water tight ,water plumbed for fire. 
Any boat with wire exposed to salt water flooding will generate chlorine gas off the wires.The simple fix is to put everything in conduit seal it and use a small air compressor to charge the system so it maintains positive pressure including the battery. not little loads tv's, etc that can be shut down from a water tight source .
ps. metal will stop fire insulate the metal


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## Kevin Sharpe (Jul 4, 2011)

Alaskanviking said:


> Likely be bad to use a metal box, as the saltwater could short the main terminals putting juice to the box or short the cell fuses.


Don't worry about shorting the battery fuses... if you have a battery fire it can melt steel 

This is what a melted Tesla looks like


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## aeroscott (Jan 5, 2008)

I didn't mention this will be a hybrid drive so I will have 400 volts on board.which will be ground fault protected and run a positive pressure on the drive unit which looks like it will be a chevy volt at this point.
My metals come from a metals junk yard so I have access to stainless steel like 304L,316L,347 and on occasion inconel and monel.
Does any one know how hot the battery fire can get. I think ss can take 2300 f. without burning though.


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## john61ct (Feb 25, 2017)

Alaskanviking said:


> LFP cells also take up a lot of space and are just as dangerous as the tesla batteries on a boat


Complete hogwash!

A tiny fraction of the thermal runaway risk.


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## john61ct (Feb 25, 2017)

Using these systems for auxiliary House power storage is completely different from propulsion usage, getting past even .1C discharge for any length if time, like running a 1000W microwave is considered a very high rate.

Few people get anywhere near .5C as a charge rate, usually tiny solar rates apply.

I completely agree that as long as you are alone on your boat far from civilization, no worries feel free to be dangerous.

But most boats do make use of marina at least occasionally, and that usually requires insurance.

And many nations require insurance just to cruise in their waters legally, most notable in the Med.

There is no ABYC spec doc for LI House batts as yet, and I'm pretty sure the committee currently working on it is only considering LFP.


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## Kevin Sharpe (Jul 4, 2011)

Getting back to the technical aspects of Tesla battery module reuse, we've been looking at pressure equalisation and humidity control within our battery boxes and came across this rather interesting part;

STEGO Drainage Device

"Condensation can occur in enclosures with high protection types by variations in temperature. The use of a DD 084 drainage device allows the removal of the condensate without losing the maximum IP66 protection type. The specific characteristic of the water permeable membrane ensures the drainage of the condensate via capillary action. The unique construction also prohibits the ingression of splash water into the enclosure."


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## oudevolvo (Mar 10, 2015)

Interesting find!
How much water are you expecting? This kind of device is desgined to get rids of drops of water, right?
With those breather valves in place it should not be too much, should it?
On the other hand it can be a great safety feature in case of a coolant leak within the box.

Would adding a moisture absorber within the box be a good idea / of any help?


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## aeroscott (Jan 5, 2008)

I wounder if Tesla uses desiccant at the air intake. Thinking of using a desiccant pack after the air compressor to dry the air. 
Another idea is to use my 02 concentrator which I use for mild steel cutting/welding oxygen supply. No running out of 02 ,going to the welding supply ,spending money only to carry a massive bottle home and run out in a day or so and do it all over again.
Back on point the purge side discharges nitrogen and about 4% argon( argon,would like to use for my tig welding to save another bottle/expense etc. but no separator is available that I know of.) Run that discharge into the battery/component/wiring system and no atmospheric oxidation can occur.This out put can be used to protect food , welding rods, etc.


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## aeroscott (Jan 5, 2008)

oudevolvo said:


> Interesting find!
> How much water are you expecting? This kind of device is desgined to get rids of drops of water, right?
> With those breather valves in place it should not be too much, should i
> 
> ...


Not much deeper then 5 or 6 ft. says the commercial diver.lol


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## Kevin Sharpe (Jul 4, 2011)

oudevolvo said:


> How much water are you expecting?


Hopefully none  My build is very much an experiment to see what does and does not work when using Tesla Modules.

It's interesting to compare Nissans sealed (and pressurised?) battery box with Tesla's which operates at atmospheric pressure. I guess the battery chemistry and fire risk led them down different paths.



oudevolvo said:


> Would adding a moisture absorber within the box be a good idea / of any help?


Possibly... I'm going to fit a humidity sensor and endoscope inspection port in the hope that we can gather some evidence to help future builds


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## GoElectric (Nov 15, 2015)

I'm definitely not so much in the Safety Camp as Kevin and Lars and others are, but even I think using Tesla batteries is pretty experimental, and not a great idea for boats. 

It sounds like you have some technical abilities, but even if you could do it, the actual cost and time spent and eventual weight when you include a bunch of safety mods vs. an off-the-shelf solution make me wonder.

Everybody wants more, more, more capacity, but maybe you can find ways to use less energy, add solar or lose some weight somewhere-else to take-on LiPOs. If it is just about the money, you are playing in the wrong sandbox, as you won't save any $$ DIY if you do it right.

Git 'er gone quicker using those batteries mentioned, and get back to sailing and diving and what you bought the boat for in the first place.


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## nucleus (May 18, 2012)

*Tesla in a Sailboat*

Weight seems less important in a sailboat, most boats I have sailed have thousands of pounds in their keel. 

So, I would lean towards a less flammable chemistry like LiFePo4... Lower energy density, higher power density, and much less prone to thermal events.


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## GoElectric (Nov 15, 2015)

*Re: Tesla in a Sailboat*



nucleus said:


> Weight seems less important in a sailboat, most boats I have sailed have thousands of pounds in their keel.
> 
> So, I would lean towards a less flammable chemistry like LiFePo4... Lower energy density, higher power density, and much less prone to thermal events.


And.... made for boats, not just prismatics? That is what I'm recommending - BMS built-in, as quick and safe as you can get.


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## john61ct (Feb 25, 2017)

Yes, many insist that packaged LFP systems with proprietary BMS built in are the only safe marine alternative to lead banks.

They call anything else DIY or a "bare cells" approach, and dangerous.

But **with the right knowledge and skills**, not your average sailor, IMO a safe system can be built from 2-3 strings of large prismatic LFPs and off-the-shelf components, as long as there are protections against:

overvoltage from charge sources
undervoltage from consumer loads
charging at too low a bank temperature

Charge/discharge rates are usually part of the overall design, but if not then guard against those as well.

CP and robust wiring infrastructure is a given.

Intra-string balancing is a controversial issue, many professional installers of the expensive systems disable that functionality as unnecessary and risky / complex.

The ABYC committee is reportedly taking a functional approach to its recommendations, so some level of DIY will be allowed.


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## brian_ (Feb 7, 2017)

*Re: Tesla in a Sailboat*



nucleus said:


> Weight seems less important in a sailboat, most boats I have sailed have thousands of pounds in their keel.


Sure... in the keel. Put a huge mass of battery higher up, and you'll need even more in the keel for stability. Plus, the more weight in the boat, the lower it sits, so like any vehicle a boat has a load capacity.

Battery in the keel area would be nice... but not very accessible.


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## john61ct (Feb 25, 2017)

Custom keel AS the battery would be killer, auto-watering system of course.

What an incentive to coddle for maximum lifespan!

Would need to be really slick bolt-on/off system, yes a maintenance issue, but having to unbolt it every 8-10 years better than completely ignoring them, as that nice GFM couple discovered in Florida 

Or just make it LFP and be done, few people keep their boat **that** long. . .


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## Kevin Sharpe (Jul 4, 2011)

I recently went to see a Model X that had been involved in a frontal crash. The resulting fire was so intense that it melted the front motor and some of the aluminium chassis members 

What I found surprising was that only one of the battery modules had any signs of physical damage (the one at the front of the battery pack on top of the twin module stack) but even this module still had voltage consistent with other modules. Clearly the physical damage to this battery module was the result of external heat and that did not start a secondary fire within the battery itself 

I'll post some photos of the modules at a later date.


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## prensel (Feb 21, 2010)

Kevin Sharpe said:


> I recently went to see a Model X that had been involved in a frontal crash. The resulting fire was so intense that it melted the front motor and some of the aluminium chassis members


I wonder why most of the pictures of burned Tesla's i have seen all seem to have something happening at the front and the battery packs seem to be fine.
Why is that ? Does it have something to do with the motors or what is there in the front that seems to be fire-trigger-happy ?


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## aeroscott (Jan 5, 2008)

He ran into a Ford Pinto.LOL


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## Jimbo69ny (Feb 13, 2018)

aeroscott said:


> I wounder if Tesla uses desiccant at the air intake. Thinking of using a desiccant pack after the air compressor to dry the air.
> Another idea is to use my 02 concentrator which I use for mild steel cutting/welding oxygen supply. No running out of 02 ,going to the welding supply ,spending money only to carry a massive bottle home and run out in a day or so and do it all over again.
> Back on point the purge side discharges nitrogen and about 4% argon( argon,would like to use for my tig welding to save another bottle/expense etc. but no separator is available that I know of.) Run that discharge into the battery/component/wiring system and no atmospheric oxidation can occur.This out put can be used to protect food , welding rods, etc.


They do in the Tesla Rav 4 pack. 

https://youtu.be/7ZLst_4N4Sw?t=96

I think that part is what you are talking about.


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## electro wrks (Mar 5, 2012)

Kevin Sharpe said:


> I recently went to see a Model X that had been involved in a frontal crash. The resulting fire was so intense that it melted the front motor and some of the aluminium chassis members
> 
> What I found surprising was that only one of the battery modules had any signs of physical damage (the one at the front of the battery pack on top of the twin module stack) but even this module still had voltage consistent with other modules. Clearly the physical damage to this battery module was the result of external heat and that did not start a secondary fire within the battery itself
> 
> I'll post some photos of the modules at a later date.


This looks like a flammable liquid fed fire, typically gas or diesel in a ICE vehicle. In this case the liquids are small amounts of hydraulic fluid, coolant, refrigerant(?) and gear lube in the reduction box(did I leave something out?). The intensity of the fire does seem out of proportion to the amount of liquid fuel(s) involved. Are there any magnesium or magnesium alloy parts used in the front of the Tesla? As another fuel source, I guess there is quit a bit of plastic in the frunk structure and cover.

I wonder if there was a continuous HV arc, as an ongoing ignition source, that added to the intensity of the fire?


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## kennybobby (Aug 10, 2012)

Where is the HV DC-DC converter located? The HV electric heater? The HV air conditioning compressor? Any of these high voltage loads represents a location that could be the source of ignition. Aluminum melts at 660C, 1220F, much lower than steel so it doesn't have to be a very intense fire to turn a Tesla into a puddle.


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## brian_ (Feb 7, 2017)

Kevin Sharpe said:


> I recently went to see a Model X that had been involved in a frontal crash. The resulting fire was so intense that it melted the front motor and some of the aluminium chassis members


Interesting. It's amusing how the fire highlights which structural and chassis bits are steel (rust-coloured now), and which are aluminum. Only a couple of surprises there, such as the steel bumper reinforcement bar.


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## Karter2 (Nov 17, 2011)

This is not the same vehicle is it ..? California ? (Some confusion as to Mod S or X )
The similarities are huge, front accident, fire, melt down , battery intact.!
https://patch.com/california/mountainview/fiery-crash-blocks-highway-101-mountain-view.


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## Kevin Sharpe (Jul 4, 2011)

I'm working on the P100 pack and have started identifying the connectors used for cooling.

The module connector is a VOSS quick connect 246 NS8 elbow plug. I've attached the data sheet and the company website is here.

I'm working on the part numbers for the "Y" connectors


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## electro wrks (Mar 5, 2012)

Here are some details of a recent tragic fatal accident involving a Model X: https://www.teslarati.com/tesla-statement-fatal-model-x-crash-ntsb-investigation/

In the original Tesla blog post, Tesla addresses the battery pack design relating to the accident and subsequent fire: 
"Tesla battery packs are designed so that in the rare circumstance a fire occurs, it spreads slowly so that occupants have plenty of time to get out of the car. According to witnesses, that appears to be what happened here as we understand there were no occupants still in the Model X by the time the fire could have presented a risk. Serious crashes like this can result in fire regardless of the type of car, and Tesla’s billions of miles of actual driving data shows that a gas car in the United States is five times more likely to experience a fire than a Tesla vehicle."

A cautionary note for all of us using these batteries.


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## Kevin Sharpe (Jul 4, 2011)

electro wrks said:


> A cautionary note for all of us using these batteries.


Absolutely!


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## Kevin Sharpe (Jul 4, 2011)

Jack from EVTV had some excellent info in his latest video


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## electro wrks (Mar 5, 2012)

If there is any doubt about the intensity of a Tesla battery fire check out yesterdays fire in California. https://youtu.be/9VtbBKnG97c


The video ends before the fire is completely out. It does look like the fire is going out, maybe confined in the separate compartments of just a few of the modules.


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## john61ct (Feb 25, 2017)

https://electrek.co/2018/05/10/tesl...ng-fire-crash-ntsb-investigate-fire-response/

The investigating agency had to "fire" the Tesla engineers from "assisting" with their investigations.

More https://www.autoblog.com/2018/05/11/a-list-of-tesla-car-fires-since-2013/

And think of the **millions** of dollars and IQ point-hours invested in preventing precisely this from ever happening!


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## Karter2 (Nov 17, 2011)

electro wrks said:


> ?....... It does look like the fire is going out, maybe confined in the separate compartments of just a few of the modules.


 I didnt think the M3 pack has separate compartments ?
But yes, it will be interesting to find out wat caused this fire to end,....as well as the cause of it starting.


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## electro wrks (Mar 5, 2012)

Karter2 said:


> I didnt think the M3 pack has separate compartments ?
> But yes, it will be interesting to find out wat caused this fire to end,....as well as the cause of it starting.


Instead of 15 compartments (There's a pair of modules together in the front compartment of the 85-100kWh vehicles) as in the Model S and X, the model 3 has 4 compartments running longitudinally. In the 3 the blow-off vents, as far as I've seen, are located at the back-end of the compartments venting to the underside rear of the car. Not to the sides of the vehicle as in the design of the S and X.

It looks like the vents in this case (a Model S) did their job and directed the flames and hot gasses away from the passenger compartment. And, the fire may have been contained by the fire resistant compartments to just the modules directly involved, and not spread to other modules.


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## kennybobby (Aug 10, 2012)

Wow those flames were really throwing out some distance to the side.

if it did burn up all the combustibles and extinguish on it's own, then that seems like quite an accomplishment and design success with respect to safety in the rare event of a cell/module fire, especially if it was contained to only a few of the module sections and didn't catch their neighbor modules or the passenger compartment.


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## oudevolvo (Mar 10, 2015)

Does anyone know where the coolant diverter valves are mounted in a Model S?

In your opinion, what are the chances that the electrical connectors are not melted on this car?


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## Kevin Sharpe (Jul 4, 2011)

oudevolvo said:


> Does anyone know where the coolant diverter valves are mounted in a Model S?


See attached image...

#13 Four–way diverter valve



oudevolvo said:


> In your opinion, what are the chances that the electrical connectors are not melted on this car?


If the connectors you're referring to are mounted in the front of the car then it's unlikely they survived... the fire damaged Model X that I've seen up close destroyed everything in front of the firewall.


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## oudevolvo (Mar 10, 2015)

Thanks, yes, I'm looking for the connectors for those diverter valves (both 3-port and 4-port). 
I'll contact them whether they can check before I drive over to see for myself (it's a 3 hour drive).
By the way, where are you getting those nice diagrams from?
Is there some kind of Tesla service manual available somewhere?


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## Kevin Sharpe (Jul 4, 2011)

oudevolvo said:


> Is there some kind of Tesla service manual available somewhere?


You can buy cheap Tesla Service Manuals from our Russian friends... an internet search will find them. They don't have the very latest info but cover most of the Model S versions up to the facelift model.

I do have access to the latest official Tesla manuals but they are pricey to buy... we made it manageable by working as a group and sharing the manual... maybe you could do something similar in the NL?


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## Karter2 (Nov 17, 2011)

kennybobby said:


> Wow those flames were really throwing out some distance to the side.
> 
> if it did burn up all the combustibles and extinguish on it's own, then that seems like quite an accomplishment and design success with respect to safety in the rare event of a cell/module fire, especially if it was contained to only a few of the module sections and didn't catch their neighbor modules or the passenger compartment.


 That would be wishful thinking requireing a very select set of circumstances.
There seems to be only one "flame vent". Near the front of the pack, so there has to be a flame path from the rear most modules to the front !
I have seen module "dividers" , but i dont see any fireproof separators between modules .


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## electro wrks (Mar 5, 2012)

If you take a close look at the module compartments (except the front two modules in the 85- 100kWh batteries) , between each module there are two layers of metal, a narrow air space, and two layers of silicone mica sheets. The silicone mica sheets are good up to ~1000 degrees C and have good electrical insulating and low thermal conductivity properties. Tesla has done their homework in this area. Let's hope it's enough to use these batteries safely.


We should all follow Tesla lead if we're going to safely use these modules in DIY applications.


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## Karter2 (Nov 17, 2011)

So if there is a "thermal event". (Fire) in one of the middle or rear modules, how do they vent out of the casing. ??


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## boekel (Nov 10, 2010)

they vent out the side, there are burn-flaps at every module.
between the modules, where the cables / watercooling runs are silicone seperators.







































this is the steel deflector, you can see it directs the flames to the underside of the car.

http://boekel.nu/foto/17/2017-01-tesla/index.htm


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## SWF (Nov 23, 2007)

oudevolvo said:


> Only info I have found on these so far is by WK057 in
> https://teslamotorsclub.com/tmc/posts/1149103/


I am curious about the reason for the locations of the two thermistors on each of the tesla modules. They are mounted on the outside can of the cells that are close to the main terminals on the module. There is no way to monitor the temperature of each cell in the module, so perhaps they are just sampling two cells as representative of the other cells in the module. The other thing that crossed my mind is that by monitoring the temperature of the cells closest to the terminals, they would also potentially pick up any heat generated by loose terminal connections. They may also give an idea of the inlet and outlet coolant temp as described by WK057 in the link above, but the coolant connections are at the other end of the module, and I would have thought they would mount the thermistors to the actual coolant tube rather than the battery can.

I am mounting new 100K NTC thermistors to the modules that will work with the ZEVA slave BMS boards I am using, and will probably just duplicate the locations used by tesla.


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## Kevin Sharpe (Jul 4, 2011)

Tesla battery module fire


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## brian_ (Feb 7, 2017)

Kevin Sharpe said:


> Tesla battery module fire


Or for those for whom the embedded YouTube player doesn't work:
My first Tesla Battery Fire

It's hard to say who is more stupid: the "professional" who built this piece of crap, or some of the YouTube commenters.


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## electro wrks (Mar 5, 2012)

brian_ said:


> Or for those for whom the embedded YouTube player doesn't work:
> My first Tesla Battery Fire
> 
> It's hard to say who is more stupid: the "professional" who built this piece of crap, or some of the YouTube commenters.


 Yeah, but you have to be impressed by how candid and honest they are about the mistakes that were made(among them: no BMS, no active cooling) and even posting a video like this in the first place. If this doesn't convince people not to trifle with these modules, I don't know what will.

A few things I learned from this video in addition to the very important safety issues I've been harping about and mostly ignored on this forum for years are:

1) Train up a Tesla sniffing dog. It looks like the dog provided an early warning of impending cell failure

2) Don't try to blow out the initial small fire like it was a birthday candle!

3) Do your initial projects with the modules at a friend's shop, not your own.

4) Spin the event as reason why patrons should give you even more money on your Indiegogo page. 

5) Make sure your land lord lives many miles or towns away!

Please don't think I'm trying to be flippant in this laugh or cry situation. This could have been a big disaster with people hurt or worse, and serious property damage.The consequences of this type of fire, even though it might be remote when a BMS and active cooling are used, are so dire it can't be ignored. Isolate the modules from each other with flame and explosion proof barriers. Have an outlet(s) that directs the hot gases and flames away from the occupants and the vehicle. And, above all, use a good BMS and active cooling.


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## prensel (Feb 21, 2010)

It looks like it wasnt charging when it got fire or did it ?
So what triggered the thermal-runway ?


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## boekel (Nov 10, 2010)

prensel said:


> It looks like it wasnt charging when it got fire or did it ?
> So what triggered the thermal-runway ?


It was... and you can see the first thing the guy reacting does is unplugging it:

https://youtu.be/WdDi1haA71Q?t=187


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## Kevin Sharpe (Jul 4, 2011)

electro wrks said:


> Yeah, but you have to be impressed by how candid and honest they are about the mistakes that were made...


odd then that the video was edited at 3:14 when many people suspect a charger was unplugged (watch white dog leap forward in slow-motion and cable 'appear' by the mans foot). Personally I think it would be a lot more "candid and honest" if they said exactly what went wrong


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## electro wrks (Mar 5, 2012)

Kevin Sharpe said:


> odd then that the video was edited at 3:14 when many people suspect a charger was unplugged (watch white dog leap forward in slow-motion and cable 'appear' by the mans foot). Personally I think it would be a lot more "candid and honest" if they said exactly what went wrong



Yes, you're right. They didn't mention the charger or charging details. I think they said there is an earlier build video for this vehicle. Maybe there are more details in it.


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## boekel (Nov 10, 2010)

Kevin Sharpe said:


> odd then that the video was edited at 3:14 when many people suspect a charger was unplugged (watch white dog leap forward in slow-motion and cable 'appear' by the mans foot). Personally I think it would be a lot more "candid and honest" if they said exactly what went wrong


There is indeed a short jump (maybe a couple of frames), might be the security cam starting a new file...

The cable that appear is coming from his hand, after he unplugged it he threw it on the ground. (if you replay at 0,25x speed easy to see).

my bet is still on 24V Lead-acid charger.
and/or misuse due to the way he handles the modules.


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## kennybobby (Aug 10, 2012)

*Burning Miss Daisy*

It originally had 6 6V Trojans, so 36V lead acid charger?

Lots of footage of sawsall and plywood, but not a voltage measurement to be found.

Such a rush to get it running, you would think they could at least fasten the steering wheel to have control while on the road..?


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## prensel (Feb 21, 2010)

I have personally experienced a thermal runway with Panasonic 18650 cells but only on the 'bottom' side after too much/low decharging to <2.5V each and immediate re-charging. After 5 minutes of charge the cells started 'popping' and overheating and one thing led to another. They were certainly not lighting like fire-crackers as seen on the video but the end result was similar: black and burned cells. 



The power of overheated 18650 cells is pretty impressive and something to think about when designing 'after-market' (= non-Tesla) battery boxes...
This one looks impressive at @4:09 https://www.youtube.com/watch?v=cMlfBKd_hz8


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## Kevin Sharpe (Jul 4, 2011)

"Tesla Battery Fire, What Went Wrong?"


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## Tony Bogs (Apr 12, 2014)

The founders of Tesla triggered the EV transition when they put a lot of Li-ion laptops cells in parallel.
Unfortunately, those high power/energy cells they needed can exhibit thermal runaway.
Placing a lot of cells in parallel increases the risk of runaway. We have seen a few spontaneous combustions of packs in production model S cars. 

The 700 mile safe batteries that may cause a disruptive transition are coming. 
Examples: www.xnrgi.com and keracel.com.
Especially xnrgi looks promising, because existing silicon wafer factories can be utilized to ramp up production at high speed. 

I'll be back with my builds and SiC evaluation projects. The safe cells will make it to market eventually and the very important 24/7 stuff, that is still taking up all my energy and time, will end at some point. 
Yeah, that's right, never been a fan of Arnold in his movies, but I really like him as a ICE car salesman in an EV promo video.


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## Duncan (Dec 8, 2008)

*We have seen a few spontaneous combustions of packs in production model S cars*

*In your dreams!*

The only "spontaneous combustion" that has ACTUALLY happened has had significant physical damage FIRST

Hitting something big and nasty on the road bed or in at least one occasion somebody lifting the carpets and SHOOTING the battery


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## brian_ (Feb 7, 2017)

Tony Bogs said:


> The founders of Tesla triggered the EV transition when they put a lot of Li-ion laptops cells in parallel.
> Unfortunately, those high power/energy cells they needed can exhibit thermal runaway.
> Placing a lot of cells in parallel increases the risk of runaway...


If lots of cells in parallel is the problem (which I doubt), no new technology is needed for the solution. Most EV manufacturers do not use massive numbers of small cylindrical cells, instead placing a small number (typically 2 or 3) of much larger pouch cells in parallel.


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