Well can anyone help me out? Ive been wrenching on my vehicles for 30yrs and have never ran across anything like this. I have a 98 i30t and it started acting up and not starting. But throw the jump pack on it and it would start. So wondering what was going on i wired a little digital meter up to the battery. Becausei could tell when the alternator would start charging. So after i start the car about 10 to 20 mins the alternator will kick on. The meter will read 11-12v and after i start the car it will slowly go down. Sometimes it gets down to 8v it has a hard time to even stay running then it will kick on and start charging. 13.5v then if i s*** it off , as long as its not over 6hrs it will charge when i start it. I really don't know what, how, or why? Ive cleaned all thw ground connections under the hood. Anybody know what is going on? I replaced the alternator 1yr ago.