Nintendo Switch starts to get hot after reconnecting battery

Hello guys

I have a problem with my switch. It has custom firmware on it, with autoRCM enabled. After not using the device for a long time the switch did not want to boot (load via payload injection). I was trying all kinds of solutions, letting it charge over night etc. etc.

I then wanted to check if my battery was fully drained and couldn’t charge because of that. I opened up my switch, disconnected the battery and tested it (2.7 Volt). I then reconnected the battery to my switch. When I do that I get a very loud coil wind (I guess) and the switch gets very warm. This did not occur before, so i am a little bit surprised here. I still can’t boot or interract with the device in any way and I am scared because of the coil wind + hot parts.

I was just wondering if you guys had any idea what the reason for this behaviour could be.

Thank you very much

Which parts are getting hot?