# Battery Box For Tesla S Batteries



## alexbeatle (Jul 28, 2020)

Hi folks,
Planning a Tesla Model S battery box - 8 pieces: 2 rows, 4 high. It'll be a bench to sit on top of.
Any suggestions on the box material? Is cooling fans ok to have to ventilate? Any other advice or challenge somebody faced with one?
Thanks in advance.


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## brian_ (Feb 7, 2017)

alexbeatle said:


> Planning a Tesla Model S battery box - 8 pieces: 2 rows, 4 high.
> ...
> Is cooling fans ok to have to ventilate?


Why would you use cooling fans with modules that have built-in liquid cooling?


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## alexbeatle (Jul 28, 2020)

brian_ said:


> Why would you use cooling fans with modules that have built-in liquid cooling?


These would be more for any heat that could be trapped inside (ex. from ambient temp. high,), or to promote general air flow. The modules themselves would definitely be liquid cooled.


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## Tremelune (Dec 8, 2009)

I could see having some circulation fans, but I wouldn't bother until the temp inside the box was shown to be the weak link in the cooling change. My guess is that it won't have much effect all.

I'm curious to see what people are building. I was gonna build my box out of aluminum angle iron and some plastic sheeting to keep out dirt and fingers, possibly with inlet and exhaust fans as described above (my pack is air-cooled Leaf modules).


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## alexbeatle (Jul 28, 2020)

I'm


Tremelune said:


> I could see having some circulation fans, but I wouldn't bother until the temp inside the box was shown to be the weak link in the cooling change. My guess is that it won't have much effect all.
> 
> I'm curious to see what people are building. I was gonna build my box out of aluminum angle iron and some plastic sheeting to keep out dirt and fingers, possibly with inlet and exhaust fans as described above (my pack is air-cooled Leaf modules).


Thinking the box needs to be a little more secure than have plastic walls?


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## Tremelune (Dec 8, 2009)

Secure from what? Fire? I have an extinguisher between my legs, and the batteries are usually at their hottest when the car is being charged and unattended...If there's a fire in that box of metal, I think the game is over anyway...

Anyone have any good resources on how to build battery boxes...?


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## alexbeatle (Jul 28, 2020)

Tremelune said:


> Secure from what? Fire? I have an extinguisher between my legs, and the batteries are usually at their hottest when the car is being charged and unattended...If there's a fire in that box of metal, I think the game is over anyway...
> 
> Anyone have any good resources on how to build battery boxes...?


I'm, like you, looking for the best practices, hence the thread. I'm just thinking if a fire in a metal box - it's contained, plastic will start to melt.


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## electro wrks (Mar 5, 2012)

Here's one of the original battery enclosure patents from Tesla describing the potential fire danger and their proposed design in response: US20100273034A1 - Battery pack enclosure with controlled thermal runaway release system - Google Patents
There are later patents that describe the actual system now in use in the Model S and X. Here's one of those patents: US8557416B2 - Battery pack directed venting system - Google Patents


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## brian_ (Feb 7, 2017)

Other than relief venting to handle problems in the pack as described in the excellent links provided by electro wrks (and as implemented by every manufacturer, not just Tesla), I don't see any point in ventilation, and I'm not aware of any production EV with liquid-cooled modules which provides air circulation to the pack case.


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## brian_ (Feb 7, 2017)

alexbeatle said:


> I'm just thinking if a fire in a metal box - it's contained, plastic will start to melt.


True... I have yet to hear of a production EV which uses a polymer (plastic) battery pack case - although there could be one - and there is good reason for that.


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## electro wrks (Mar 5, 2012)

Tesla does have another small vent or two near the top of the battery enclosure in addition to the many pop-off side vents. I'm not sure how it works. In an ideal world, it would relieve small amounts of pressure and vacuum and keep water and dirt out at the same time. Thanks to boekel for these photos.


















Front, top cover flipped upside down with vent in center.










Close-up, inside view of valve. The part# brings this up: TA292-R Breather Valve - AGM Container Controls


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## justdave2 (Mar 3, 2019)

The modules are significant weight ~70lbs/31Kg and in a vehicle should be very secure. No thin aluminum or plastic should be used without some serious engineering (like the original model S tray). Built some DIY powerwalls and was amazed at how 6+ modules would start to deflect square steel tubing frames. Please be careful with these. Also, consider some kind of engine hoist design if you will have an 8-module + wire, contactors, battery box you plan to drop into a car.


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## remy_martian (Feb 4, 2019)

alexbeatle said:


> I'm, like you, looking for the best practices, hence the thread. I'm just thinking if a fire in a metal box - it's contained, plastic will start to melt.


Ever heard "died of smoke inhalation"?

Some plastics give off cyanide when they burn.

Others, chlorine gas

Odds are you are not smarter than any factory automotive engineer, so pay attention to what they've done in all your "research" vs deciding you like the idea of a watching a slow melt as your nervous system shuts off.


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## alexbeatle (Jul 28, 2020)

remy_martian said:


> Ever heard "died of smoke inhalation"
> 
> Some plastics give off cyanide when they burn


Hence, I vote for metalic.
Comes to question: steel vs. aluminum? How thick? 
Any suggestions?


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## remy_martian (Feb 4, 2019)

alexbeatle said:


> These would be more for any heat that could be trapped inside (ex. from ambient temp. high,), or to promote general air flow. The modules themselves would definitely be liquid cooled.


Heat can't get "trapped" - it's being sunk into the liquid cooling system. It's also not "cooled better" by putting fans in the battery box.

The neat thing about the fans, though, is it increases first responder safety. If you can keep them running, the car will be a pile of ashes and metal globs by the time they arrive.


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## remy_martian (Feb 4, 2019)

alexbeatle said:


> Hence, I vote for metalic.
> Comes to question: steel vs. aluminum? How thick?
> Any suggestions?


That question can't be answered because you have not defined what the box does and what loads it has to carry. Your fabrication skills and available resources also come into the decision.


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## SouthCoastEV (Jul 16, 2019)

You said it will be a bench, is there anything nearby that can get in the vents (assuming you still want the cooling fans)? Is this going on a vehicle, or some other application?


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## alexbeatle (Jul 28, 2020)

SouthCoastEV said:


> You said it will be a bench, is there anything nearby that can get in the vents (assuming you still want the cooling fans)? Is this going on a vehicle, or some other application?


Going on the vehicle.nothibg should get into fans as planning on small computer fans. As mentioned most of cooling/heating is via liquid.


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## remy_martian (Feb 4, 2019)

We have a technical term we use in engineering for the kind of airflow you'll get over a traction battery with computer fans:

"fart in the wind"

You need to hone your listening skills. It's impossible to talk and listen at the same time.


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## alexbeatle (Jul 28, 2020)

remy_martian said:


> We have a technical term we use in engineering for the kind of airflow you'll get over a traction battery with computer fans:
> 
> "fart in the wind"
> 
> You need to hone your listening skills. It's impossible to talk and listen at the same time.


If you have nothing to say, please try not participate in discussions, which could be useful to other in this forum.
Thanks in advance.


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## remy_martian (Feb 4, 2019)

I've said it to you before, I'll say it a third time because you suck at listening. In a liquid cooled battery box, fans do NOTHING but pull dust in. Get them out of your head.


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## Jb24601 (Aug 29, 2019)

.


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## alexbeatle (Jul 28, 2020)

Jb24601 said:


> Fwiw


Thanks!
Considering this design with angles for shelving the modules inside. Paint with liquid rubber on the inside to avoid conductivity. 2 bays, 4 tall each.
Wasn't sure what the thickness is. Looks like define steel to me. 2mm maybe!?


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## remy_martian (Feb 4, 2019)

Liquid rubber? 

Avoid conductivity?

Shelving?

Wut?

The man says he can't imagine 4 up, and along you immediately come with...a 4-up IKEA-shelved design.

The Tesla modules sit on mounting tabs - they are NOT designed to sit on "shelves" and those mounting "rails" in a Tesla battery are solid and thick. 

Given where you plan to put your batteries, and that most crashes are while moving forward, to avoid the box becoming a proctology tool, your box of modules needs to withstand around 15 tons of horizontal force. 

A 4-up box that is floor mounted is going to be a heavy mofo and keeping it from tearing out of the floor will be challenging. It will have a higher-than-stock CG, meaning it'll have the performance handling characteristics of a hay wagon.

As far as fire goes, a mere dent or puncture of any cell will likely light it off. In a 4-up, you pretty much guarantee you'll light off the stack of 4 - at least, if one mere cell lights off. With your fans idea, the full pack will likely light off.

With what you're considering for a design though, you'd never die from burns...the box will smack you flat like a mosquito in July.


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## alexbeatle (Jul 28, 2020)

remy_martian said:


> Liquid rubber?
> 
> Avoid conductivity?
> 
> ...


Suggestions?


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## remy_martian (Feb 4, 2019)

Mount the batteries by their tabs.

If you can't design a box, build and test some before they see a single battery

Figure out how you'll anchor the box to the car

Lower the CG by putting as many modules in the first layer. Even Tesla resorted to stacking...


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## alexbeatle (Jul 28, 2020)

remy_martian said:


> Mount the batteries by their tabs.
> 
> If you can't design a box, build and test some before they see a single battery
> 
> ...


Can you please share some pictures of your previous builds for inspiration. I can tell you've built a few already.


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## oudevolvo (Mar 10, 2015)

Fully agree with JB here, in my view you need boxes that give you time when you need it.
Even though my boxes are not in the interior I have chosen for stainless steel boxes with stainless steel frames holding them.
I have also added Tesla vent caps so I know where they will vent if they need to.
Updates on my development can be found on https://www.oudevolvo.nl/en/?s=Battery+box&lang=en


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## alexbeatle (Jul 28, 2020)

oudevolvo said:


> Fully agree with JB here, in my view you need boxes that give you time when you need it.
> Even though my boxes are not in the interior I have chosen for stainless steel boxes with stainless steel frames holding them.
> I have also added Tesla vent caps so I know where they will vent if they need to.
> Updates on my development can be found on https://www.oudevolvo.nl/en/?s=Battery+box&lang=en


Beautiful box!


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## Jb24601 (Aug 29, 2019)

.


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## remy_martian (Feb 4, 2019)

remy_martian said:


> Mount the batteries by their tabs.
> 
> If you can't design a box, build and test some before they see a single battery
> 
> ...


By "tabs", to clarify, I don't mean the electrical posts, but the FR-4 rails that run on the sides of the module.


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## itchyback (May 28, 2014)

I have designed a aluminium box to hold four modules stacked on top of each other and verified it with FEA. 
The box is 3mm aluminium 5052 pop riveted (not welded) to join the corners. This far exceeds Australian design rules for registered cars to withstand 20g forward impact, 15g side impact and 10g rear/rollover impact. 2mm aluminium would also work but as its prone to fatigue and impacts from rocks etc from underneath, use 3mm. 
It mounts into the car with an angle steel seat 20x20mmx 3mm and square section attaching it to the car chassis 25x25x2. This too far exceeds the same Australian design Rules for registered cars. 
That may be enough info to get people out of trouble, but not everyone or every situation. design it thoughtfully and check with an engineer.


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## remy_martian (Feb 4, 2019)

Could you be a dear and post either a link to, or a PDF, of those rules? A lot of good parameters there.


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## alexbeatle (Jul 28, 2020)

itchyback said:


> I have designed a aluminium box to hold four modules stacked on top of each other and verified it with FEA.
> The box is 3mm aluminium 5052 pop riveted (not welded) to join the corners. This far exceeds Australian design rules for registered cars to withstand 20g forward impact, 15g side impact and 10g rear/rollover impact. 2mm aluminium would also work but as its prone to fatigue and impacts from rocks etc from underneath, use 3mm.
> It mounts into the car with an angle steel seat 20x20mmx 3mm and square section attaching it to the car chassis 25x25x2. This too far exceeds the same Australian design Rules for registered cars.
> That may be enough info to get people out of trouble, but not everyone or every situation. design it thoughtfully and check with an engineer.


Great info! Given pop rivets on the external box, how do you prevent water coming in? Say you drive over a puddle that could potentially splash onto the box.


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