TSDZ2 power loss due to stupidity

So I was messing around awhile back with one of my TSDZ2 bikes and sparked the pos terminal which resulted in total loss of power. Usually you go to the fuse and replace that and on you go but there was no fuse.....so I assumed that it was the controller and although I have changed out controllers before and know the process I didn't have one and the bike got put aside and life went on with my other bike which eventually got replaced with a Luna Z1 over a period of time.

My son finally decided that he wanted an eBike for commuting and fishing access so I offered up my working motor but adapted to the non working frame because he didn't want or need a FS bike. He lives in Vancouver and came down to my place and we spent some of the day swapping out parts and making the hardtail work again and he took it home happy as a clam at high tide.

All went well until it didn't and the other day he said that after recharging the battery it wouldn't show any power so I told him to go through all the connections. He did that and still no power so I told him to remove the plastic cover on the battery plate to see if the connections in there were good. He did and sent me a pic of the pos wire where it exits the plate fully exposed with the housing torn open and the wire mostly parted. Told him to solder the wire and see if that did it but it didn't fix it so I am assuming that it shorted out like the one I described above.

So I am assuming that the controller is the issue for both motors but just checking here for confirmation or something I might be missing? Any input appreciated.

Bike

If there's literally no power (no voltage at the battery terminals), the problem is the battery.

If there is power (full normal voltage at the battery terminals of the controller, and correct battery meter reading on the TSDZ2's display), but no response from the system after it's turned on, it could be the controller.

If there is power (full normal voltage at the battery terminals of the controller) but the system won't turn on, it could be the controller or it's display.