Best use for Tesla 3 modules with damaged cells?

[zl3ag]

First post so be gentle.

As noted by TrueSoln, here in NZ we (now) get our Tesla 3's from China and the standard range ones come with CATL LFP cells.

These are the usual 2 short/ 2 long modules but possibly easier to electrically split the cells apart than the US ones.

Difficult to physically re-configure to shorter lengths due to the single cooling tube on the bottom.

So I'm thinking that even thought the cells are pretty much brand new (2022) and there is a damaged cell at the front of module 1 and 2 due to the accident, the best use for these modules would be to leave them as they are physically, and reconfigure them to 48V modules by cutting the alloy busbar between certain cells and wiring up generic external 48V BMS modules.

Note: The above image shows a close-up of one terminal of the cell with the flexible BMS circuit board laying on top and an exposed portion of the inter-cell busbar with the oval laser weld that connects the underlying LFP cell with the busbar. Just above is another exposed part of the aluminium busbar that narrows in size, presumably as a fusible link. The plan is to dremel through that link to seperate the cells then SOMEHOW connect cables there to use as new connection points? Tig welded alloy cable?

They would then be mounted vertically in a container so that a passive cooling system could be set up using the standard Tesla cooling tubes (with external radiator on the shaded side of the container and used as a large 48V solar storage battery.

The slightly damaged cells still show a voltage, but any current demand would likely cause a fire so I would leave them in place, but disconnected. Left in place because I supect these cells might be glued down to the aluminium cooling plate and to the adjacent cells.

Although I need cells for ev conversions I think I'm better off using batteries from other vehicles for this as they are so much easier to physically reconfigure due to cells being completely seperate with their own cooling plumbing? I'm talking about Kia/Hyundai/Leaf here.

[bigmotherwhale]

I would use the whole pack without any reconfiguring (but still with the bad cells removed) for energy storage, you can get high voltage solar inverters to work with them relatively easily, do you know if the BMS is the same as the NMC version?

Edit: is that battery electrolyte that's from a split cell? If it is you should remove and dispose of it safely, you cant have that stuff about reacting with the atmosphere. Its quite toxic.

If you do need to reconfigure, it is possible to solder or spot weld onto aluminium but they were originally done with laser i imagine, nuts and bolts with terminal lugs are easy if you have the space.

TIG might be possible with all the sensitive electronic components removed but the heat generated will have to be managed and you wont be able to weld onto battery terminals directly or anything in close contact.

[zl3ag]

Thanks for the welding info.

I don't think it's electrolyte.

The car was in a very nasty accident - I think they may have hit something very solid in the passenger front corner. The alloy rim on that corner was smashed into pieces, and the top strut area ended up waaaaay back from where it should have been and the A pillar basically folded towards the passenger seat. I don't think the passenger faired very well. Part of the bodywork folded down into the passenger foot well and pierced through the bottom of the floor, the top steel of the battery pack and the opaque plastic covering the 5th cell back from the front of the pack. During outside storage water pooled in the compartment, and dripped through the hole, rusting on the way.

There is a aluminium beam in the sill channel of the Model 3. The passenger side one was shunted back inside the sill so far that it nearly sliced through the 2 rear brake lines in front of the rear wheel.

I was going 48V as I already have other stuff ready for that, although I do have higher voltage inverters, etc so I may do a stocktake before I decide what voltage to use in the end.