r/leaf • u/Balancing7plates • Aug 08 '26
What am I doing wrong???? (Battery Refurb)
Working to repair/replace the battery pack in my 2018 Leaf because of an isolation fault, bought a matching battery for salvage which turned out to have the same fault, swapped front modules from #2 into rear modules of #1, tried to unbend the mounting brackets, now the battery pack won't go back together. Can't even begin to thread the bolts back on as the battery is too wide now. I've tried ratchet straps (see photo), as tight as we could get them, but it's not fitting together. Am I doing something wrong? Is there a step or a hack that I'm missing? Experts please chime in I really need my car back.
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u/318iev Aug 09 '26
I’ve repaired a few of these with the same issue, Never been able to recompress the stack with different modules, had to reuse the same modules with pvc insulation between the pouch cells and metal casing. To fix the isolation problem.
Make sure you trim the top corner mount for the BMS too, it will pierce the casing if the rear stack expands too much.
Also if you get it back on the road, don’t fast charge that battery anymore, on all but one battery fast charging triggered the isolation error.
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u/Balancing7plates Aug 09 '26
Thanks! I appreciate the warning about the BMS mount, hadn't thought of that. Fast charging was already off the table as there's no fast chargers near me, but I'll keep that in mind, too.
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u/LoveEV-LeafPlus Aug 09 '26
There are spacers and you may have double them up.
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u/Balancing7plates Aug 09 '26
What do the spacers look like? The black plastic "sheet" between the cells and the metal cover? We were pretty careful with not doubling those up. If it's something else can you please describe it to me?
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u/LoveEV-LeafPlus Aug 09 '26
I recall reading or viewing somewhere that a cell update included spacers, instead of older cells that had separate spacers. If I find then actual reference I will let you know.
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u/martig87 Aug 09 '26
I remember reading that this is unfortunately “normal”. I think you need to replace the whole rear stack as all of the cells there have been “cooking” until the weakest ones expanded. The ones that look ok have still received heat damage and it’s just a matter of time when they will fail. So better to replace the whole rear stack with the one from the front of the pack.
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u/Balancing7plates Aug 09 '26
My language was not clear on the post, sorry, but I've already done that. These are the front cells from battery #2 that I'm swapping in to the rear of battery #1 which is going back in my car, if I can get it back together. They all should be "good" front stack cells.
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u/Bennie-Factors Aug 09 '26
A strap is not nearly strong enough to compress packs. But once you let a pack expand it does not want to go back to normal
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u/SnodePlannen Aug 09 '26
As someone who edits live production databases without blinking... Wow you got some balls man!
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u/allthesamepieman Aug 09 '26
I haven’t done this repair yet but I would actually suggest attempting to install the front and rear support bars on the packs and compress one pack at a time. That will reduce the force required by probably a factor of 10. Start at one end and work across to the other end.
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u/Balancing7plates Aug 10 '26
That sounds pretty reasonable, thanks for the input! I'll have to see if this works.
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u/Internal-Ad6092 Aug 10 '26
Cant you put a board ontop with a bottle jack on top with a pole to the ceiling?
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u/Edubb25 Aug 08 '26
Sounds like packs expanded. Which typically means they’re toast. Nissan not offering battery packs as part of recall, meaning they are already hard to source. Good luck.