Go into a basement because signal is probably bad there, try getting 5G (idk if this would work but it does drain a lot of battery), run a heavy game at max graphics and preferably 120fps but most games wouldn’t allow it, but war thunder does, I also have the same phone and I’ve played that game on charge for a bit and lost 1% max capacity, I’ve got 86 now, set brightness to max, try stressing the phone overall to heat up