Water damaged game boy micro

Trying to repair a gameboy micro with water damage. The unit before repair would not charge the battery or and the leds would not work, it would work if a precharged battery was plugged in, again without the leds working. I replaced the power management IC which was missing a pin and it now charges. Leds still don’t work. My concern is whether this system is safe to use, how does the system know when to shut off the charge current? I’d rather not detonate a battery to find out need advice