So I bought a super clean vert a few days ago, guy told me I needed to bring my own battery. Drove 3 hours away from my house, bought the vert installed my brand new battery and drove home, got about 5 minutes from pulling into my driveway and things started shutting down, dash or headlights stopped working. By the time I made it home the battery was drained and had to jump start.


Alternator test fine
New alternator fuse
Battery reads 11.7v while running and no increase at higher Rpm
If I take the battery terminals off the car it will still run for a few minutes but with hardly any power and dies immediately if I try and turn some lights on.

Why is the car still running once the battery is disconnected when the alternator isnt doing its job?

I don't know but maybe the ground wire off of the side of the alternator isn't connected? I think you'd have the heavy gauge wire, the plug with a few wires and the ground wire all coming off of the alt. Do you have all of those?