https://i.kym-cdn.com/entries/icons/original/000/010/669/Sheeeit_Banner.jpg how many nuffins did a dindu do if a dindu dindu nuffin?

i bought a second hand semi-ded UPS for dirt cheap, replaced battery and MCU filter caps, and it was great worked like that for 5 years or so then it was away from me for half a year in unknown condition and then transported to me it came with dead battery bought a new battery, plugged it in, seemed good incidentally unplugged the battery when it was plugged in a working (but not loaded) UPS, and something exploded inside with a nice bang and flash have no clue why disassembly shown a fried MOSFET not sure if it makes any sense to try to fix it but sadly .me is not Moscow, so can't buy loads of used UPSes for dirt cheap the fried one is at the right: https://tinystash.undef.im/il/4Z7EYDuSqDh47tQcw4qGjUuJv9VNfVCr24nGmvB8zZ7kdZo1ZnNtfPxyAps7zXFeg5JJvp5rj8W6zNSBAwc2Epvz.jpg no idea what it feeds, so no clue why opening it would cause a short also some sus deposit, couldn't identify the culprit: https://tinystash.undef.im/il/2QpKK6BDiUkgcMewPmmXPCyrqKTSJPRX5JCU8JAGnECakmaiHqNgDTtoBdP7huAKvJCRL4934NokVsvwES6QBezF.jpg i wonder if it makes sense to dig any further or if i should write it off and buy a brand new one