I set the troublesome pack aside & made it to my doctor's appointment by switching to the official TS LI pack I happened to have with me...
I've had random loss of power events over the 6 years I've been using the LiFePO4 pack. (China, unmarked mongrel cells, reworked for smart charging.) I've had all manner of failures, usually a welded trace breaks. Not totally surprising since the use cycle involves breaking the unit down each time... it's just a lot of handling. I know the pack is charged... I have just 20 minutes of use on it. Have to be careful I don't fry myself!
I brought it it & put it on the bench, got it out of the soft travel case, removed the hard battery support tray & soft polyfoam padding, so I'm down to the pack. I started testing... I got nowhere fast. NO POWER on the Anderson SB50. I actually managed to disassemble the SB50 connector this time without destroying it.
In my efforts to stabilize the 3P7S pack, I had hot glued all the cells possible, duct taped the outside, then 2 layers of electrical tape (black sticky) to cover the contacts... then still more as wrapping to stabilize the harnesses. There was NO movement in the wires at the pack. Rock solid. I spent an hour gently cutting away & peeling the tape with scissors without shorting anything out or cutting the tiny balance leads or pulling them off with the sticky tape.
All I can find is the main power lead positive tests open. SERIOUSLY! It's a big ass wire. How can it be open? But it tests open. It has the Anderson contact soldered to one end. It has a round ring terminal soldered to the other & the ring soldered to the end of the cell. I have power through the ring terminal soldered to the cell. An open wire?
I hate the welded, now soldered tab, cells. I wish I could solder a brass machine screw to the cell, & bolt to it. I didn't have time to test the rest of the traces, but nothing visual. I need to go through the rest of the pack again.
I'm going to have to skin this big ass wire once I get it replaced... so I understand WTF. I'd have never guessed the main power lead itself.