Pressure testing battery pack

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notam2

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Joined
Sep 22, 2022
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So I recently bought a 2012 Leaf with a degraded battery and am in the process of upgrading it to a 40 kWh battery that I bought as part of a donor car.

An issue I'm having is that at some point, the previous owner of the donor car jacked up the car and missed the jack point, lifting the car by the battery pack. Or maybe some forks got it at the yard. Either way, there is a seam between two pieces of metal on the underside of the battery pack and that seam is caulked at the factory. A three inch section of the bead is no longer sealing the case, and there's maybe a 1mm or 2mm gap letting air into the battery pack.

Any idea what would be a best practice to reseal the battery pack?

Also, I found a previous post by Dala on pressure testing a pack. See:

https://www.mynissanleaf.com/viewtopic.php?t=31153

I had an idea I wanted to share on pressure testing a pack. My cpap machine is capable of accurately maintaining a pressure of 0.23 psi (approximately 17 cm of water column), so I was thinking of hooking my cpap machine up to the 'new' battery pack with some vinal tubing, a barb fitting, a check valve, and a manometer tapped in between the check valve and the battery pack. Thoughts?
 
Stupid question: what happens if you don't seal the pack? I get that is the original design goal, but what are ramifications if you don't? Doesn't mean you can't take measures to prevent water/moisture from entering the "crack"...but that's not the same as pressure sealing.
 
Stanton said:
Stupid question: what happens if you don't seal the pack? I get that is the original design goal, but what are ramifications if you don't? Doesn't mean you can't take measures to prevent water/moisture from entering the "crack"...but that's not the same as pressure sealing.
Click to expand...

See the 2012 Zero Motorcycle recall.

You want to seal the pack.
 
Stanton said:
Stupid question: what happens if you don't seal the pack? I get that is the original design goal, but what are ramifications if you don't? Doesn't mean you can't take measures to prevent water/moisture from entering the "crack"...but that's not the same as pressure sealing.
Click to expand...

To be honest, I was kind of wondering the same thing myself. If I built an unsealed power wall I doubt that I would seal it up the same as a battery pack. I suppose corrosion from humid air entering the pack could be a long-term problem. Two months ago I encountered an underpass that had three feet of standing water after a storm and had to turn around. Driving through something like that could be problematic without a sealed pack. The remote chance of that happening or the 'crack' causing a short is enough for me to want to seal it up. How hard can it be to fix a three inch "crack" anyways.

Someone suggested a polyurethane sealant called Window Weld to me. I believe it can support operating Temps from around -60 to 90 degrees Celsius. Wish I knew what Nissan used originally, though there are probably a few different products able to seal up the pack.
 
Would the modules from the new pack fit in the old case?

Personally, the only way I would trust the new pack to be completely sealed would be to make sure the mating surfaces are flat and then re-seal it with the same kind of sealant originally used. To do that would probably mean taking the pack cover off, getting it straightened out as needed and then re-installing it. It seems unlikely that a gap would open up unless the metal case was deformed somehow and in that case, I would fix the metal before re-sealing.
 
The 2011 and 2012 had a bunch of bolts holding the two case halves together. The cases were just held together with sealant on the flanges beginning in 2013. I would not trust that the rest of the flange surfaces and sealant are OK because the whole case may have been distorted (with resulting stress on the flange joints) by the improper lifting. It might be best to split the cases, repair the damage to the flanges, and use the proper sealant and procedure to close/glue/seal the battery case.

I suspect the damage was done by the salvage yard. I considered buying my 2011 back and converting it to a small flatbed pickup, but gave up after seeing damage to the underside caused by the salvage yard using a large forklift to move it.
 
Given that I'm upgrading from a 24 kWh battery to a 40 kWh battery, I don't think a brute force module replacement is the way I want to go. I don't think I can use my old lower case on the new battery as there are some subtle differences, including a PTC heater connector on the new battery that the old battery doesn't have.

I've thought about cracking open the new pack to inspect and reseal it, but I'm not sure that I'll be better off. The pack looks pretty solid. I'm actually impressed that the rest of the caulking retained its bond despite the force applied to the underside of the battery. The metal is only deformed to the extent of maybe 1mm or 2mm at most. Even if I cracked the pack open I'd probably fix the issue by patching the three inch segment where the bond isn't holding instead of tearing everything apart and resealing the entire bead. I probably can't do just one bead anyways, because breaking that bead would damage an adjacent bead...so apart from being an order of magnitude more work, I thinking I should only fix what's actually broken.

I'll likely go with a urethane patch over the three inch segment. There are some urethane sealants that can patch boat hulls watertight below the water line. If it passes a pressure test after curing then I know its sealed and I should be good.
 
notam2 said:
Given that I'm upgrading from a 24 kWh battery to a 40 kWh battery, I don't think a brute force module replacement is the way I want to go. I don't think I can use my old lower case on the new battery as there are some subtle differences, including a PTC heater connector on the new battery that the old battery doesn't have.

I've thought about cracking open the new pack to inspect and reseal it, but I'm not sure that I'll be better off. The pack looks pretty solid. I'm actually impressed that the rest of the caulking retained its bond despite the force applied to the underside of the battery. The metal is only deformed to the extent of maybe 1mm or 2mm at most. Even if I cracked the pack open I'd probably fix the issue by patching the three inch segment where the bond isn't holding instead of tearing everything apart and resealing the entire bead. I probably can't do just one bead anyways, because breaking that bead would damage an adjacent bead...so apart from being an order of magnitude more work, I thinking I should only fix what's actually broken.

I'll likely go with a urethane patch over the three inch segment. There are some urethane sealants that can patch boat hulls watertight below the water line. If it passes a pressure test after curing then I know its sealed and I should be good.
Click to expand...
I don't think you can use the new cells and controller in the 2012 case even if you open both cases and try to move everything. After thinking about it some more, I agree with your latest reseal/patch approach. If it holds pressure in accordance with the service manual test method, then you should be OK.
 
^what he said :D

The only caveat I would add is to check the condition of the patch/sealant after a day/week/month/year to make sure everything is working according to plan.
 
I used the 999MP-57302NP as specified in the manual--overall a beautiful product to work with. Required 2 tubes at $48 each--and I was being very frugal with application. 3 tubes onhand would be a good idea. And a Ryobi electric caulk gun, which was really struggling to push the material. The material is quite stiff, so bring it up to at least 80 deg F. If I did it again I would probably try a cheaper betaseal product on a test item to see if it performed the same. The foam dam is there to prevent sealant from bonding areas that cannot be accessed when cutting the shell off.

For pressure testing I used a $40 manometer from the big online retailer. A perfect tool for this job. There was a tiny leak at the top of the front arch which I was able to seal by forcing more sealant in there, and barely hit the leakage target specifiec in the manual. If you pressure test, you will need to fully tape off the whole aluminum connector plate--it leaks a lot of air.
 
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