# upgrading Miata from lead to lithium



## dtbaker (Jan 5, 2008)

Finally getting a thread started for this project.... I recently bought a '94 Mazda mx5 (Miata) which had been converted by Henry Herndon a couple years ago. Very nice build: Warp9, zilla, upgraded clutch, belltronix dc-dc using 12x Optima yellowtops w/ Rudman regs tied to the Manzanita pf20 charger.

Henry did some fine work.... very nice work on the dash, and used a panel mount cycle analyst multi-gauge. Only thing I'll have to make a big change for is to pull the dash (yuck) at some point to add heat for 4-season use.

Anyway, lead is predictably dead, and Henry decided he didn't have the time or money to upgrade to Lithium and wanted to move on to other projects....

So, I am pulling the lead and putting in 156v nominal (48 cells x 130ah CALB), and hoping to re-use everything including the battery racks with little change. Space in a challenge in a Miata! The 130ah cells are taller than Optimas, so I am going to have to rack them horizontal.

follow along!


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## dladd (Jun 1, 2011)

This is exactly the car my wife wants me to build for her! She had a Miata years ago. I'll be interested to see how you fit the 130ah cells, they are definitely taller than lead batteries. Laying on the side will make the wiring a lot more difficult I'd think, especially if they are in a large block (more than one row of cells). Are you going to put them on edge, or flat?

Were the battery racks built custom, or were they a kit? I know at least one company builds battery racks specifically for the Miata.


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## dtbaker (Jan 5, 2008)

dladd said:


> This is exactly the car my wife wants me to build for her! She had a Miata years ago. I'll be interested to see how you fit the 130ah cells, they are definitely taller than lead batteries. Laying on the side will make the wiring a lot more difficult I'd think, especially if they are in a large block (more than one row of cells). Are you going to put them on edge, or flat?
> 
> Were the battery racks built custom, or were they a kit? I know at least one company builds battery racks specifically for the Miata.


The racks were custom built... super solid and a nice layout for the Optimas. If I were doing them from scratch I would do it differently to allow vertical cells. Probably more cells in a U in motor bay, and deeper wells behind seats and trunk to allow vertical. I would also build w aluminum rails rather than steel. These racks are WAY overbuilt for the weight of Lithium cells.

144v would be an easier fit too.... the 48 cells for 156v makes it a real challenge for space.

Big goal here is to use the existing racks if possible so I don't have to invest any more time and money re-fabbing them.

I am resigned to adding 'monitor' wires to each cell out to a terminal block so I can check balance occasionally and tweak manually if need be. Once the cells are in, its going to be tough to get to the terminals.


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## dtbaker (Jan 5, 2008)

now that the cells are all top-balanced, I unhooked them and set them in the car for a little reality check on layout with actual cells.... always different than measuring with a tape and hoping for the best. The existing racks in the mid and spare tire well turned out to be just too tight to lay the cells flat, which means that I really can't get quite as many in the well as I thought, which means that even if I add a new 10 cell box between the tire well and mid rack I can only fit 46 cells (147v nominal), AND I am guessing the weight distribution will be very tail heavy. ;(

So, I am going to check the weight just as a closer to the argument, and probably going to bite the bullet and re-fab the engine bay racking and layout... which I was hoping to avoid. sigh...

The motor bay rack was 'probably' going to have to be modified a little anyway because even with the batteries stacked flat there was almost no clearance to the hood which would have presented a real design challenge in putting a lid on the batteries.


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## dtbaker (Jan 5, 2008)

Surprisingly, it looks like this layout is much better balanced than I expected. It also is heavier... I got readings on the two scales (pretty accurate cheap digital ones for just $20 each with capacity of 400# each) totalling 1450# at the front wheels, and 1495# at the rear. So, now the decision is whether its easier to modify the existing rack a little, or re-fab from scratch to move a couple more cells up front and re-balance. I haven't removed the tow bar from the front, so that would lighten the front probably another 40#; so I'd want to move a couple cells to the front if possible...

So..... the big decision is now whether to pull the front rack and modify, or start from scratch, perhaps with aluminum and move more of the cells to the motor bay to even out the weight in hopes of getting all 48 cells in the car.

sigh..... time to empty out the motor bay and ponder a little.


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## Caps18 (Jun 8, 2008)

That is a lot of batteries to fit in that car. I will be interested in seeing how far it will go, and how fast it will accelerate. I'm sure both will be really good.


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## dtbaker (Jan 5, 2008)

Caps18 said:


> That is a lot of batteries to fit in that car. I will be interested in seeing how far it will go, and how fast it will accelerate. I'm sure both will be really good.


range is not really the primary goal with this vehicle, I really only *need* 50 mile max.... with this vehicle I wanted to work backward from 'performance'. max voltage I feel comfortable putting to a Warp9 is 156v, although I think some people have gone higher, there are lots of other components that are limited to 160v without getting into 'special' stuff. I considered 100ah cells, but that would have effectively limited me to 500amp burst accel and 300amp continuous; I am beginning to think that might be just as 'quick' because of the significantly lower weight and space. But I wanted to take more advantage of the Zilla that was installed already, so with 130-140ah cells, I should be able to burst to 700 amps relatively *safely*. I'm not sure that will make up for the extra weight though in actual performance. If I had a ton of money I would consider a headway battery pack, but I don't intend to race the car, so I can't really justify the higher cost. The range of this car is more a by-product of the voltage and desire to support a *fun* amp draw without killing cells... Secondary goal is that I want to be able to tell people that yes, this car can make it to either albuquerque or los alamos from santa fe, although it would have to recharge to get home!


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## Caps18 (Jun 8, 2008)

dtbaker said:


> I considered 100ah cells, but that would have effectively limited me to 500amp burst accel and 300amp continuous; I am beginning to think that might be just as 'quick' because of the significantly lower weight and space. But I wanted to take more advantage of the Zilla that was installed already, so with 130-140ah cells, I should be able to burst to 700 amps relatively *safely*. I'm not sure that will make up for the extra weight though in actual performance.


Why would the cells be limited to 500 Amps? I am looking at purchasing 100 Ah batteries and trying to figure out if I should run at 120V or 144V. But I was thinking that the controller was what limited the max amps. I am laying out my battery box plan today, and If I could fit 38 in one box, but 45 cells would take two, I will keep it simple, cheaper, and light and go with 120V.

Most days I need just a 10-20 mile range, sometimes up to 40-50 miles would be nice in my lightweight S10.


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## dtbaker (Jan 5, 2008)

Caps18 said:


> Why would the cells be limited to 500 Amps? I am looking at purchasing 100 Ah batteries and trying to figure out if I should run at 120V or 144V. But I was thinking that the controller was what limited the max amps. I am laying out my battery box plan today, and If I could fit 38 in one box, but 45 cells would take two, I will keep it simple, cheaper, and light and go with 120V.
> 
> Most days I need just a 10-20 mile range, sometimes up to 40-50 miles would be nice in my lightweight S10.


the large format prismatics are rated for 3C draw continuous, and best not to go over 5C for more than 10 sec or so.... because the will generate a fair amount of heat internally at that rate. If the guts get too hot, bad things happen.  So, even if your controller can put out more, its not good for the health of the cells.

So, w/ 100ah cells, you'd have a fairly safe 300 amp continuous. At 120v I would guess an s10 would need close to 300 amps to maintain highway speed. It would draw less at 144v.... go with 144v!

144v x 100ah might get you a 50 mile max, but it'll be very close, just as a guess. If you really NEED the occasional 50 miles, you might want to consider 156v (48 cells) x 100 ah.


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## drgrieve (Apr 14, 2011)

Of course the new gray calb cells changes all of this. They put out 10 to 12C quite comfortably. Which is a massive improvement over the blue ones.

Another way to determine how much you can push the cells is to monitor the sag. Around 2.5 to 2.7 volts under load is the trade off between fun and longevity.


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## dtbaker (Jan 5, 2008)

drgrieve said:


> Of course the new gray calb cells changes all of this. They put out 10 to 12C quite comfortably. Which is a massive improvement over the blue ones.
> 
> Another way to determine how much you can push the cells is to monitor the sag. Around 2.5 to 2.7 volts under load is the trade off between fun and longevity.



does anyone know what they changed to enable such a big improvement in max output? and..... how long can put out 10C before damage (internal heating)?


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## Ziggythewiz (May 16, 2010)

There have been many changes lately with different anode/cathode configurations to increase output, so I suspect it's largely that along with tweaking the additives for better cold weather performance.

People scare me with all the talk of 10+C though. Just because it can dish it doesn't mean it's happy about it, and the only way to find out is to wait years. People are already being disappointed by the almighty A123 cells.


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## Caps18 (Jun 8, 2008)

Most of the time, I will just be driving around on city streets stopped at red lights. I don't plan on accelerating for minutes, and even the rare highway trips are only at 65mph for about 10-15 minutes (others highways around here are 55mph). So, if they could handle that, then I would be fine. 

Do I really 'need' to take this to the drag strip, no. But I would like to see what numbers it would get one time though. So, it would very rarely ever get floored in the normal day to day driving. I will be trying to use as little power as possible in reality.


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## dtbaker (Jan 5, 2008)

so.... making progress on 'getting the lead out'. Unfortunately will have to re-design and fabricate a new front rack as I just cannot fit all the new cells in with current platform sitting so high above the motor. I am going to HAVE to make a new rack allowing two 'banks' of cells on either side of motor....

anyway, I now have some components that I'd like to sell to anyone still using or about to use AGMs. I've got the 12x Rudman Regulators off and packed up, along with inter-unit wires and even 6x ratchet straps. The regulators run about $75 each retail from Manzinita, so I am hoping to recover a little cash to apply to the upgrade!

Oh, and if anyone is building a Miata with Optimas, this front rack will be out and available in a couple days. I'd hate to sell for scrap if someone could use it!


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## onegreenev (May 18, 2012)

dtbaker said:


> does anyone know what they changed to enable such a big improvement in max output? and..... how long can put out 10C before damage (internal heating)?


It's magic sauce, thought you knew that already. 

I do not think you or anyone can pull 10C long enough for any damage to occur.


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## dtbaker (Jan 5, 2008)

onegreenev said:


> It's magic sauce, thought you knew that already.
> 
> I do not think you or anyone can pull 10C long enough for any damage to occur.


well.... If I had gone with 100ah cells, the Zilla could crank out 10C until either the cells vented, or the motor zorched...

In retrospect, the 100ah cells would have been plenty as all 48 of the 130s are proving hard to fit into the Miata. Just a matter of self control, it'll be hard to NOT use the zilla to its full capacity.


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## onegreenev (May 18, 2012)

Once you actually get your beast moving the need for that full 10C drops like a rock. Try holding 500 AMPs from your cells for any given distance or time. You will notice it will begin to drop fast as the need diminishes. 10C for a quick trip down the track is possible but not for much longer and you'd need a 2K Zilla or the new Shiva to attain that kind of power consistency. If you could hold it for minutes then you might get some damage. 

My controller can hold 800 AMPS solid as long as I can feed it but when my car launches the need of the motor no longer needs that full 800 amps and begins to drop fast. Actually my cells only gave me a bit over 600 amps last time out. But still at 6C it was impressive but there was no way the needs of the motor could sustain a full 6C for long. A couple seconds before it began to drop off.


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## GizmoEV (Nov 28, 2009)

dtbaker said:


> well.... If I had gone with 100ah cells, the Zilla could crank out 10C until either the cells vented, or the motor zorched...


You might want to read the Zilla manual to see how long it really can do 1000A.


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## dtbaker (Jan 5, 2008)

GizmoEV said:


> You might want to read the Zilla manual to see how long it really can do 1000A.


with liquid cooling, as mine has, I'd bet the zilla would last longer than the cells or motor without damage.


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## GizmoEV (Nov 28, 2009)

dtbaker said:


> with liquid cooling, as mine has, I'd bet the zilla would last longer than the cells or motor without damage.


Funny. All Zillas are liquid cooled. I take it you haven't read the manual since you said you are betting. I'm not talking about the Zilla dieing. I'm talking about its ability to maintain 1000A. Actually at 200V it is only rated at 950A from the battery and that goes down as the battery voltage goes up. Do you know what the continuous current rating is? It is not 1000A.


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## dtbaker (Jan 5, 2008)

GizmoEV said:


> Funny. All Zillas are liquid cooled.


not intended to be funny. My comment pertains to the fact that since there is no standard radiator or airflow, different installations will have better cooling. My particular one is pretty good, using the stock heater core place in direct flow at the grill.



GizmoEV said:


> I take it you haven't read the manual since you said you are betting. I'm not talking about the Zilla dieing. I'm talking about its ability to maintain 1000A. Actually at 200V it is only rated at 950A from the battery and that goes down as the battery voltage goes up. Do you know what the continuous current rating is? It is not 1000A.


I have in fact read the manual and do understand that the zilla 1k kicks out 1000 amps MAX. ok fine... more precisely then... I would bet that the POWER the zilla 1k can put out (156v x 1000 amps peak) would damage the motor or the batteries before itself. Why are you giving me a hard time about this?

The relevant part of all this is that I had decided to go with 130ah cells over the 100ah cells not because I really needed the extra range, but because wanted to lower the max C the cells would see under full power acceleration to prevent damage.

In retrospect, and especially if the new cells have higher output without damage, I'd probably go with the 100ah.... 

The purpose of this build thread is to talk about the build, not argue semantics.


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## TheSGC (Nov 15, 2007)

Do the CALBs like being on their sides? I was told not to put my CALB 180AH on their sides, just keep them vertical for expansion and cooling reasons.


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## dtbaker (Jan 5, 2008)

TheSGC said:


> Do the CALBs like being on their sides? I was told not to put my CALB 180AH on their sides, just keep them vertical for expansion and cooling reasons.


the word I got direct from CALB engr support guy was that vertical is prefered, flat side is fine, edge side ok, but not prefered.... upside-down not ok. 

I am ending up having to re-design the front rack anyway, I just could not get all the cells in on top of the rack that was designed for the Optimas. So, I would have gone with horizontal (which has the advantage of combining hold-down with clamping support on the big side of the cells), but am ending up with everything vertical after all.

Working on the layout now, as I just got the old rack completely out yesterday. Its looking like I will have 12 cells in spare tire well, 12 behind passengers, and 24 under the hood.


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## GizmoEV (Nov 28, 2009)

dtbaker said:


> not intended to be funny.....Why are you giving me a hard time about this?....


We seem to be on completely different planets on this. You were implying two things about the Zilla. One that yours was liquid cooled and others weren't. Second, that the Zilla was a 1000A continuous controller which it isn't.

Now back to your regularly scheduled upgrade thread...


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## dtbaker (Jan 5, 2008)

Had a few weeks of inaction, but managed to get a little done over the last couple days.... fabbed a little shelf for the vacuum pump, and another for the Hairball, which WAS on the old battery rack.

tried out my new MIG welder on some thin 1/16" aluminum L for brackets.... man thats tricky! burnt holes and melted holes on low settings. Going to take some practice. I've not worked w/ MIG before, so not quite sure about best wire feed speeds and how to hold things so that the wire doesn't start welding before the gas has gotten going for little short welds in thin material.

Working on finishing up the wiring for the vac pump, sensor, SSR next...


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## Ace_bridger (Nov 22, 2011)

dtbaker said:


> Had a few weeks of inaction, but managed to get a little done over the last couple days.... fabbed a little shelf for the vacuum pump, and another for the Hairball, which WAS on the old battery rack.
> 
> tried out my new MIG welder on some thin 1/16" aluminum L for brackets.... man thats tricky! burnt holes and melted holes on low settings. Going to take some practice. I've not worked w/ MIG before, so not quite sure about best wire feed speeds and how to hold things so that the wire doesn't start welding before the gas has gotten going for little short welds in thin material.
> 
> Working on finishing up the wiring for the vac pump, sensor, SSR next...


Looking good!!!


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## mk4gti (May 6, 2011)

Monitoring your blog, keep it up, Dan!


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## coulombKid (Jan 10, 2009)

mk4gti said:


> Monitoring your blog, keep it up, Dan!


The internal battery heating is a function of internal resistance. Newer more robust chemistries will tend toward lower internal resistance and hence larger allowable discharge ratings. As the batteries age and loose capacity the internal resistance will be creeping up. The temperatures here in Arizona and to a lesser degree in New Mexico favor the more conservative discharge curves. Nissan failed to provide liquid cooling on the Leaf and are, as we speak, harvesting some bitter usage data on the 2012 model here in Arizona. Mitsubishi is selling electric cars in CA but I haven't seen any here in Arizona. The Nissan experience is most likely giving them a wait-and-see mind set on the issue.


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## mizlplix (May 1, 2011)

Dan: When MIG welding aluminum, you need some stainless steel wool to clean the area. Then I would always "blip" the trigger once to start the gas flowing and while the afterflow timer (and gas) is running you can start the weld with a gas shield in place.

Always work the wire back and forth in the direction of the weld to force the puddle to clean its self and to distribute the heat a little. Especially on thin stuff.

You can also clamp a bar of brass behind the weld seam to support it and pull some heat away.

Keep the wire "stick out" length to a minimum to allow the full voltage at the weld.

Miz


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## dtbaker (Jan 5, 2008)

mizlplix said:


> Dan: When MIG welding aluminum, you need some stainless steel wool to clean the area. Then I would always "blip" the trigger once to start the gas flowing and while the afterflow timer (and gas) is running you can start the weld with a gas shield in place.


thats great advice, I'll have to listen if my unit lets the gas run for a bit after a blip. I got just a little millermatic 211 with a spoolmate for the AL. seems to be too hot even on the lowest setting for the thin (1/16") alum I was experimenting with. I think I need to just spend a little time welding some scraps for practice..... that and perhaps a brass heatsink for the thin stuff might help me a lot.


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## dtbaker (Jan 5, 2008)

wired up the SSR and digital pressure sensor I am using instead of big ol' square D mechanical switch.... Hope I got it right! Not sure the diode is necessary, or if I have it in the right direction.  any comments before I power it up?


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## TEV (Nov 25, 2011)

dtbaker said:


> wired up the SSR and digital pressure sensor I am using instead of big ol' square D mechanical switch.... Hope I got it right! Not sure the diode is necessary, or if I have it in the right direction.  any comments before I power it up?


Usually I see a diode being use with an electromagnetic relay in parallel with the coil. Not sure if / where you need a diode with a SSR.


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## dtbaker (Jan 5, 2008)

TEV said:


> If I am not rong , the way you connected the diode it would make a short circuit between +12V pump and ground.
> Usually I see a diode being use with an electromagnetic relay in parallel with the coil. Not sure if / where you need a diode with a SSR.


I'm not sure either, which is why I posted the picture.  The little arrow is pointed toward the 12v+, which was what was suggested in schematic, but I dunno if it is really *required*, and I want to be sure before I apply power!

I am hoping that Tesseract or one of the other EE types chimes in.....


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## TEV (Nov 25, 2011)

Good luck and good night


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## TEV (Nov 25, 2011)

dtbaker said:


> I'm not sure either, which is why I posted the picture.  The little arrow is pointed toward the 12v+, which was what was suggested in schematic, but I dunno if it is really *required*, and I want to be sure before I apply power!
> 
> I am hoping that Tesseract or one of the other EE types chimes in.....


If it's like in the diagram then it's ok. My bad , I was assuming that the bolt is the catode (-), usually one will chose a diode with the catode at the bolt so if you install it on a heat sink you don't have to isolate the heat sink from the body of the car (-).


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## dtbaker (Jan 5, 2008)

TEV said:


> Usually I see a diode being use with an electromagnetic relay in parallel with the coil. Not sure if / where you need a diode with a SSR.


I would just as soon take it out to simplify. The application note documentation showed a diode across the load.... but if its not a required thing, I'll just take it out!


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## Coulomb (Apr 22, 2009)

dtbaker said:


> I would just as soon take it out to simplify.


I would not. SSRs are solid state devices, which are sensitive to voltage spikes. Turning off an inductor creates a voltage spike. A pump is likely quite inductive.

I'd use a multimeter to verify the direction of the diode. The diode should not conduct when power is applied to the pump.


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## dtbaker (Jan 5, 2008)

Coulomb said:


> I would not. SSRs are solid state devices, which are sensitive to voltage spikes. Turning off an inductor creates a voltage spike. A pump is likely quite inductive.
> 
> I'd use a multimeter to verify the direction of the diode. The diode should not conduct when power is applied to the pump.



THEREs an explination that makes sense to a mechanical guy. ok, ok, I will leave the diode in there, not hurting anything, and cheap insurance for the SSR I gather. I powered it up and all seems well. Direction I think is good... the tail (Anode=Ass) to negative, and Point to Postive. 

I'm thinking there are probably prettier ways to wire those things than with a glob of solder on the end that looks like a darning needle end?


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## dtbaker (Jan 5, 2008)

ok, vac pump is 'complete', made a little bracket for hairball, brackets for zilla+contactor and stuff, and started on under-hood battery boxes. coming together fast now.... hope to make more progress this weekend.


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## Ziggythewiz (May 16, 2010)

What kind of tape is that over your terminals?


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## dtbaker (Jan 5, 2008)

Ziggythewiz said:


> What kind of tape is that over your terminals?


just duct tape to keep plastic bits out of the terminal holes, and minor protection in case I drop something while working.....


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## dtbaker (Jan 5, 2008)

battery boxes for the front are coming along.... just have to add mounting tabs to chassis and a couple holes for inter-box cabling.


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## Ziggythewiz (May 16, 2010)

dtbaker said:


> just duct tape to keep plastic bits out of the terminal holes, and minor protection in case I drop something while working.....


Oh, okay. Guess you have to scrub the residue? Maybe it's the heat/humidity here but I can't even use electrical tape on anything without making a stick gooey mess.


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## dtbaker (Jan 5, 2008)

Ziggythewiz said:


> Oh, okay. Guess you have to scrub the residue? Maybe it's the heat/humidity here but I can't even use electrical tape on anything without making a stick gooey mess.


this duct tape doesn't leave much.... garage is cool and tape was only on for a little while. I haven't done the final sanding+noalox yet, so no worries. I like to hit the terminal tops with a sanding block, and slap a little noalox on just before I install the terminal bus bars to get a nice fresh flat non-0xidized surface.


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## Ziggythewiz (May 16, 2010)

Sounds good. The boxes look great! Someday I'll make some...


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## dtbaker (Jan 5, 2008)

Son Thomas helped with fabrication and plastic-welding the mounting 'ears' on the front rack this weekend. Next step is to drill a couple holes for the inter-box cables, and mount the circuit breaker, charger and dc-dc units before final install.


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## GizmoEV (Nov 28, 2009)

How does the strength of those boxes compare to identical ones made out of aluminum?


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## dtbaker (Jan 5, 2008)

GizmoEV said:


> How does the strength of those boxes compare to identical ones made out of aluminum?


well.... there is all kinds of 'strength'.

1/4 thick sheet polypro versus 1/8" aluminum is:
- considerably cheaper
- non-conductive (safer versus the accidental cable brushing the edge!)
- lower thermal conductivity, better for cold as it won't transfer nearly as fast when ambient is cold, and will hold internal heat longer.
- very tough, won't take a dent or work-harden when bent
- easy to weld and work with
- won't corrode, no paint needed, no problem with water, acid, etc
- about the same weight, or perhaps less, I havn't looked up the weight of full sheets to compare.

...if carefully designed, most stress is either in shear or compression, so it's plenty strong. trick is to avoid long spans in bending or cantilevers without gussets... would have the same issue with aluminum sheet.

standing in the boxes and jumping up and down, the box doesn't even flex except the flat bottom a little right under my feet. The battery weight will be spread to the edge, so pretty much no flex.


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## GizmoEV (Nov 28, 2009)

Ok, so basically if the welding/assembly is done correctly either one would be fine. I know that Aluminum can crack along welds if it isn't done properly. Does the plastic welding have similar issues? If not I think I could get the hang of plastic welding much faster and for less cost than aluminum welding.


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## dtbaker (Jan 5, 2008)

GizmoEV said:


> Ok, so basically if the welding/assembly is done correctly either one would be fine. I know that Aluminum can crack along welds if it isn't done properly. Does the plastic welding have similar issues? If not I think I could get the hang of plastic welding much faster and for less cost than aluminum welding.


plastic welding is WAY easier than welding thin aluminum, and equipment way less expensive. high quality hot air welder is less than $300. material could be polypro, ABS, or HDPE. I used polypro because first battery boxes were for floodies and needed to be acid-proof. I might use ABS next time mostly because it comes in black and wouldn't show all the goobers and dirt so much.

other option with aluminum of course is to mostly bend and rivet. thin AL pretty much needs a TIG welder and lot of practice.


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## PTCruisin (Nov 19, 2009)

Dan,

You have inspired me to look at polypro battery boxes for my Miata conversion. I am transferring the 38 TS 100Ah cells from the PT Cruiser to the Miata so they will be slightly smaller than the CALB 130s that you are using. I am going to cut an opening in the trunk floor for about 20 cells and put the remaining 18 under the hood.

I was wondering what you are going to do to secure the tops of the battery boxes (and the batteries) and if you are going to fabricate a polypro box for the trunk as well?

Really nice work!

Ralph


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## Caps18 (Jun 8, 2008)

I've riveted sheet aluminum before, but I went with a 'plastic' box that you can buy at Amazon for my battery box. $200 and all I have to do is add the support brackets to mount it to the frame of the truck.

It weighs 37 lbs and can hold the weight of 45 100Ah LiFePO4 batteries (350lbs), and it is also waterproof. They come in a bunch of different sizes. I couldn't have done better making my own box out of polypro or Al.


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## dtbaker (Jan 5, 2008)

PTCruisin said:


> Dan,
> 
> You have inspired me to look at polypro battery boxes for my Miata conversion. I am transferring the 38 TS 100Ah cells from the PT Cruiser to the Miata so they will be slightly smaller than the CALB 130s that you are using. I am going to cut an opening in the trunk floor for about 20 cells and put the remaining 18 under the hood.
> 
> ...


thanks.
I used the poly for the rear in my Swift first, which started as a FLA build. I used steel frame edges because I was worried about the 3x weight of the lead, and possible whacking from curbs/speed bumps. comfortable with 'edgeless' box design for the Miata and LiFePO4 cells.

the top I am going to fab a 'bar' across the top, like I did for the front rack in Swift, and probably thin clear plexi to keep out dirt, water, and fingers.

My Miata will end up having 24 cells in front, 12 behind passengers, and 12 in wheel well. Front is a VERY tight fit with 130ah cells much taller than 100ah or the Optimas that were in there.

Mostly just trying to re-use the racks that the initial build had installed designed for Optima yellowtops. They are steel-L with coroplast sides.... not crazy about it, but not wanting to do a complete re-fab if I can avoid it. I'm going to try to get by with fabbing 'spacers' to hold cells in existing space, which is a little too big, and avoid complete re-fab for the middle and back racks.


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## marc02228 (Jan 15, 2011)

Looks really good!

What dimensions do the front-boxes have and how much higher did you build the box in front of the motor?


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## dtbaker (Jan 5, 2008)

marc02228 said:


> Looks really good!
> 
> What dimensions do the front-boxes have and how much higher did you build the box in front of the motor?


well.... I built the 3 boxes first, then laid them in the bay propped up with clearance and tried to get the angle to follow the hood line. There is not a lot of clearance with the 130ah cells as they are a lot tller than 100ah. I also allowed an extra 1/2" on the bottom for insulation. The back corners basically have no clearance to the brakelines, and the middle is very close to the motor cable mounting bolts.... Its a pretty tight fit. 

After I had the three boxes welded together, I tacked on 4x 'mounting brackets' to match the mounting bolt holes (weld nuts) the previous builder had welded into the chassis. Doing it again, I probably would use 6x of smaller rivet-nuts to avoid welding on the chassis.

At this point I have hand-fit the boxes and haven't measured/documented exact dimensions of how things worked out..... HHHmmm, perhaps I will though, and offer the plans for some nominal fee to pay for the time it will take to draw up neatly.

The Miata is such a nice car to convert, there are probably a lot of people that couple save a few hours by having a dimensioned design to work from. I suppose I could even jig up and fabricate the whole box for sale, but shipping would be a killer.

I'll add some more pictures when the rack is 'done' complete w/ holes for cables, etc.....


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## njloof (Nov 21, 2011)

dtbaker said:


> The Miata is such a nice car to convert, there are probably a lot of people that couple save a few hours by having a dimensioned design to work from. I suppose I could even jig up and fabricate the whole box for sale, but shipping would be a killer.


That's pretty much what the folks at http://evmiata.com do... I found it really handy when designing my particular build to know exactly how much battery space I could count on... That, and my welding skills aren't that good.


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## dtbaker (Jan 5, 2008)

njloof said:


> That's pretty much what the folks at http://evmiata.com do... I found it really handy when designing my particular build to know exactly how much battery space I could count on... That, and my welding skills aren't that good.



hhmmm, looks like their boxes are designed for lead, and not deep enough for taller Li cells like the 130ah for sure... I was somewhat surprised to see they ignore the whole volume taken up by the gas tank to avoid removal headaches. I wonder how many they sell 'pre-fab'?!


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## dtbaker (Jan 5, 2008)

catching up on progress I made in a few hours, over the last couple weeks. 

glued feet on the Belktronix dc-dc, and finished up the front rack... except for lids for the cells.


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## dtbaker (Jan 5, 2008)

finished up mounting the controller cooler (heater core) to front grill, installing it, and plumbing... ready to fab lids for the battery rack and drop cells in soon!


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## skooler (Mar 26, 2011)

Hi Dan,

I'm intrigued by your battery boxes!

I think I might have to use polypro on the RX8 now.

Any 'gotchas' that you can think of?


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## dtbaker (Jan 5, 2008)

skooler said:


> Hi Dan,
> 
> I'm intrigued by your battery boxes!
> 
> ...


only downside of the natural white polypro is that it it shows messy welding or cuts more than black ABS. In 1/4" sheet they are about the same strength, but the polypro is more acid resistant, but that's a non-issue with a lithium build. Only trick to cutting /working is to use a coarse blade rather than a fine one; that will generate too much heat and weld the cut back together behind the blade!

Its a bit of a pain to clean up too because the tiny chips have a little static cling, and get everywhere.... I'm sold on plastic battery boxes because of the non-conductivity, no-paint, relatively light, and strong enough if you design well.


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## dtbaker (Jan 5, 2008)

front battery box is finally bolted in, complete w/ dc-dc, charger, circuit breaker mounted. I also have lids made.... so now doing final prep on cells and will be loading 'em up over the next few days! Should be rolling soon after fabbing some quick box/lids for the mid and rear battery boxes.

There are more images on my site, but here are two views from the sides.... pretty tight fit with these 130ah cells! 

Also included one image with son Thomas stress testing the box; pleased to report almost zero flex! Turned out very sturdy....


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## dtbaker (Jan 5, 2008)

big milestone today.... finished up under the hood! Just have to rack 12 cells behind passengers, and 12 more in spare tire wheel well. Almost ready to roll!


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## PTCruisin (Nov 19, 2009)

dtbaker said:


> big milestone today.... finished up under the hood! Just have to rack 12 cells behind passengers, and 12 more in spare tire wheel well. Almost ready to roll!



This looks great Dan!


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## dtbaker (Jan 5, 2008)

PTCruisin said:


> This looks great Dan!


thanks.... getting to the stage where the end is in sight, and I can't wait to get this thing on the road!


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## dladd (Jun 1, 2011)

looks great! I'm planning on doing a similar battery box for my soon to be added front cells and have a few questions...

How are the boxes attached to the car? How are the batteries attached to the boxes? Is there any metal support structure for the Polypro, or do you think it's strong enough on its own? How think is the material you used? I recall you did a cool little thing with a strip of Polypro along the top edge of the cells on your other car to hold them down in the boxes, are you doing that again?


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## dtbaker (Jan 5, 2008)

dladd said:


> How are the boxes attached to the car?


if you go to my website and step thru the construction of the boxes you'll see the 'ears' on the sides. They match up to 4 big weld-nuts that Henry had put in for his rack. If I were to do it from scratch I would recommend 4 or 6 maybe a little smaller, and no need to weld in if you get the heavy-duty 'Riv-Nuts' that are like drywall anchors only heavier. You could drill into chassis rail, install 4 or maybe 6 and be in great shape.



dladd said:


> How are the batteries attached to the boxes?


well.... first, they are a very tight fit. actually have to use rubber mallet to get the last cell in. second, the little AL angles I use to hold the plexi lids on have screws that stick thru the walls a little JUST at the top of the cells, locking them down. third, the lid itself is pretty close to the top of the terminal bolts even if the screw tips didn't hold the cells in cae of inverted rollover..... should be fine.



dladd said:


> Is there any metal support structure for the Polypro, or do you think it's strong enough on its own?


no metal edges.... very strong. I actually jumped up and down with one foot in each side.... pretty much no flex or problems. the ears to chassis are short and gussetted, and with the front box and rails in back, it is amazingly stout structurally.



dladd said:


> How think is the material you used?


1/4"



dladd said:


> I recall you did a cool little thing with a strip of Polypro along the top edge of the cells on your other car to hold them down in the boxes, are you doing that again?


no need for extra strip with screws sticking thru.... I didn't like those strips anyway as they blocked vertical airflow. I switched to using wood rails between cells with screws into ends, and then screwed lid down from top into the wood. Little different with these boxes as I used little AL brackets along edges of lids.


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## dtbaker (Jan 5, 2008)

batteries are all in, everything wired up, wheels are turning!
.... ready to register, insure and get on the road ....
few little details to clean up, but ready to roll before xmas!


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## dtbaker (Jan 5, 2008)

titled, licensed, and registered....
LEGAL in the road!

and wow, what fun to drive! I have to think about ome way to record acceleration and/or make a digital video for youtube... Its really fun when running controller wide-open. Still figuring out how to limit things for the non experienced without making it too tame.


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## mk4gti (May 6, 2011)

Hey that's awesome! good work  I bet the swift will "feel" slow after you get hooked to 1k amps 

I'd like to know where you found the "braided battery straps" as seen in this picture?

Thanks


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## dtbaker (Jan 5, 2008)

mk4gti said:


> Hey that's awesome! good work  I bet the swift will "feel" slow after you get hooked to 1k amps


yeah.... I thought the Swift was fine (30kW thru an ADC8") till I experienced 100+kW through a Warp9. Very hard to dial back. A whole new grin when you can break tires loose on acceleration... Its wicked fun!



mk4gti said:


> I'd like to know where you found the "braided battery straps" as seen in this picture?


got'em from evtv. CALB and most others seem to ship only with the standard length for 'row' connections, and do not offer the different lengths required to step over to a different 'column.'


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## TheSGC (Nov 15, 2007)

dtbaker said:


> yeah.... I thought the Swift was fine (30kW thru an ADC8") till I experienced 100+kW through a Warp9. Very hard to dial back. A whole new grin when you can break tires loose on acceleration... Its wicked fun!
> got'em from evtv. CALB and most others seem to ship only with the standard length for 'row' connections, and do not offer the different lengths required to step over to a different 'column.'


I still have yet to pump 1K through my FB1-4001a yet, I'm waiting for water cooling and better weather so I can install my new circuit breaker.

I ended up using the connectors from CALB and just did a slight modification on the holes to make then step over to the other 'columns'.


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## dtbaker (Jan 5, 2008)

TheSGC said:


> I still have yet to pump 1K through my FB1-4001a yet, I'm waiting for water cooling and better weather so I can install my new circuit breaker.


WHAT?! how could you resist cranking it up to see what it could do for 10 seconds! The controller, motor, and batteries will be FINE for 10 seconds. 
The cooling is a good idea for long-term though. A little tranny cooler and a LIang pump into a 1 liter reservoir does the trick perfectly




TheSGC said:


> I ended up using the connectors from CALB and just did a slight modification on the holes to make then step over to the other 'columns'.


yeah, the 100ah cells its SHORTER to jump columns, so I just kinking the connectors a little more. With the 130s I needed significantly longer connects so ordered the 80mm straps.


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## Ziggythewiz (May 16, 2010)

TheSGC said:


> I ended up using the connectors from CALB and just did a slight modification on the holes to make then step over to the other 'columns'.


Depending on the size you can get connectors for a different size cell to do end-end connections.


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## dtbaker (Jan 5, 2008)

Ziggythewiz said:


> Depending on the size you can get connectors for a different size cell to do end-end connections.


yes you CAN... but you can't order x number of different lengths for cross connections from calibpower.com as they ship only with full set of 1/cell all same length. So x-connects have to be ordered elsewhere. The braided straps from evtv are just one solution.... but a pretty good one, although expensive, as the braids are forgiving for anything shorter than max.


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## Ziggythewiz (May 16, 2010)

dtbaker said:


> yes you CAN... but you can't order x number of different lengths for cross connections from calibpower.com


I have. The only issue I had was the shipping starts at $15 so better to order more than less.




TheSGC said:


> from CALB and just did a slight modification on the holes to make then step over to the other 'columns'.


What tool(s) did you use to make the mod? Most of the ones I tried ended up mangled or took excessive work.


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## dtbaker (Jan 5, 2008)

Ziggythewiz said:


> I have. The only issue I had was the shipping starts at $15 so better to order more than less.


THATS the point. I knew how many I wanted in the original order... x 'regular' bars, and y 'x-' bars, and they couldn't do it so I had to order separate from evtv for the longer ones this time.





Ziggythewiz said:


> What tool(s) did you use to make the mod? Most of the ones I tried ended up mangled or took excessive work.


shorter is easy, I used a socket as a 'form' and bent.... http://www.envirokarma.org/ev/gallery/110227_connector_adjust.htm

longer is messy and reduces contact area and solid area for bolt/washer which I didn't like and so went with braided.


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## Ziggythewiz (May 16, 2010)

I ordered some 70ah bars along with my 40AH cells.

Yeah, shortening is easy, I just do that by hand. I wish they came with the elongated holes on both ends.

I think the longest bars are only ~70mm anyway, so bigger than that you'd have to use the braided straps. I've been meaning to try and make some of my own, but too many things to be done.


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## TheSGC (Nov 15, 2007)

Ziggythewiz said:


> What tool(s) did you use to make the mod? Most of the ones I tried ended up mangled or took excessive work.


I just used a vice to flatten the connector then I clamped it down to the bench and use my DeWalt hand drill to elongate the holes slightly. I only needed 5mm so I just slightly elongated both holes until they aligned.

I have the CALB 180AH and I think CALB only has one size buss bar that they ship.


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## dtbaker (Jan 5, 2008)

TheSGC said:


> I have the CALB 180AH and I think CALB only has one size buss bar that they ship.



They have different sizes for different cells, but won't mix sizes for cross connects.... you get x connectors for x cells. I've asked calibpower to consider stocking a few 'extras' in appropriate lengths that could be swapped out in initial order/shipment, but so far they haven't.


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