Tuglyfe Box Mod Needs Reviving

[Acindivo]

TL;DR Friend put battery in tuglyfe box mod in series when both are supposed to go positive side up. Now only the battery that sits in the slot that my friend didn't .... up in works.

My buddy and I were chilling and he wanted to use my tuglyfe box mod w velocity v2 rda. He put the batteries in series rather than both positive side up. The instant he put the second battery in, the positive side of the battery touches the negative side of the box which created an orange light at the connection. He pulled it out and threw it on a rock outside. (I recycled this battery) A day later, I put some new samsung 25Rs into it to use it but I realized the battery life was nothing like it was. I put the batteries on the multimeter and the battery that was in the side that got ....ed up was fully charged while the battery on the right was completely depleted. The negative connector (the one that had the incident) in the box is rough and blueish (I can add pictures if needed). Not sure what to do with this. I really don't want to trash this mod. All help is appreciated.

 

[Bad Ninja]

You most likely either melted a connection or fried the Mosfet.

Check all the connections, wires, solder first.
If they are all good, it's the Mosfet.

 

[Ben85]

I'd be cleaning up the bluish connection and seeing if that solves the issue. I'd doubt it's the mosfet as it is still firing.

 

[Acindivo]

You most likely either melted a connection or fried the Mosfet.

Check all the connections, wires, solder first.
If they are all good, it's the Mosfet.

Specifically what do you recommend me doing? I'm pretty new to this tugboat box mod and not familiar with its internals. Only understand enough to get by. Also, to clean up the connection, I rubbed some iso alc on it and it seemed most of the color has gone, but its still rough. Maybe this may be the problem?