My girlfriend bought a 1992 Geo Tracker for a beater car to take fishing. I noticed immediately that the battery light was on, the owner said dash lights have been on since he’s owned it. So the second day driving it died, I jumped it and got it back home and ran some test with a multimeter, battery was dead obviously, but what surprised me is with the car running, it was showing 61 volts! So I figured okay the voltage regulator is bad, I took it out and had it bench tested they said it’s good, so I brought them the battery, they tested and said it had a bad cell, so I bought a new one, threw everything back together and it was running fine. Throughout the night the battery light popped back on, so I hurried up and got it home, checked again, now it’s showing 30 volts. I’m at my wits end, and don’t even know where to begin, so can someone please help, I’ve never encountered this before.