The leaves do not need to contact each other in any other point than at the battery terminal screw which compresses them into one flat ring.
Sent from Mail for Windows 10 From: Mr. Sharkey via EV Sent: Wednesday, October 2, 2019 4:18 PM To: [email protected] Cc: Mr. Sharkey Subject: Re: [EVDL] LiFePO4 Thermal Imaging Opinions? Well, it looks like this issue may have been one of my own making. When I went to remove the cell interconnect strap, both bolts into the cell terminals were "just snug", not tight. Apparently I got distracted when completing the BMS card swap, and didn't torque the bolts. The straps are made up of four .025" "leaves" of copper stock, with a little hickey bend in the center for mechanical relief between the cells. A sleeve of heat shrink tubing protects the center of the completed strap, and holds it together for assembly on the pack. This was one that I had disassembled to repair, probably because it had been intentionally bent by the previous owner to do something that it wasn't intended to do. When I took it off, it didn't look at all unusual on the top, and the bottom looked fine, it had been in complete contact with the cell terminals by the appearance of the anti-corrosion grease. Inside was a different matter. I cut the heat shrink off and found this: http://www.westlanetv.org/~sharkey/evgfx/Hot_Strap.jpg The four leaves from right-to-left are top-to-bottom, respectively, and the bottom of the photo is the end that was connected to the too-warm cell in the IR photo. I wish I had been able to use some brand name green abrasive pads instead of the dollar-store pretend ones, cleaning the discoloration out of the straps would have been much easier. Afterwards, I hit them with real white Scotchbrite, then gave them a shine with Brasso for good measure. A wash with denatured alcohol, and I put them back on the cells. I'm going to go all over the battery and check all the fasteners for proper torque before putting the cover back on the pack. In the long term, I think I might build a new strap. If this one was so abused that I needed to take it apart to use it again, there may be some issues with the leaves not making as complete of a contact with each other as new, flat straps made from new stock. I don't have any .025 stock, so I use five leaves of .020 copper to build new straps. I hope to have another session with the IR camera next week to see if my efforts to correct this little screw-up have been successful. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/index.html INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20191002/d9339c05/attachment.html> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/index.html INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
