I've discovered another treachery of ebike wiring. Wire color means nothing and can't be trusted.
If you have a pair of wires, one carrying 40 volts and the other the ground, red can be the ground and black can be the 40 volts.
If you have a set of mating connectors, the wire that is red on one plug can be black on the other and vice versa. So, if you plug them together, red becomes black and black becomes red after passing through the mated connectors
@MLE_online awful. My son and i are rebuilding the LA battery for my old e-bike.
The fuse was bypassed with a wire-nut.
And the battery terminals were soldered on.