Good morning forum, on Sunday my daughters car would not start so I used my jump box and got it started and when it started I noticed that the battery and ABS light was on so I drove it a few miles to my house and noticed they would come on and off. Once I got to my house and turned off the car it started right back up with no issues with the light still coming off and on initially and going off but if I drove it they would pop in and out. So I unhooked the positive terminally for just seconds and the care stayed running so I assumed it was a bad battery and I bought one and changed it. Once I installed the new battery the car started up with no lights but when I drove it I saw the lights again with the brand new battery installed. Now It seems to may be a bad alternator so I left the car parked with the new battery installed, didn't drive it or anything and when I went to start it yesterday the car had to be jumped again, how did the new battery die with out running or anything, also could it be a bad alternator?

 

In the first dead battery episode was the battery dead and you needed to jump it?

Unhooking a battery terminal with the engine running on a system having an alternator can damage the alternator voltage regulator.

The ABS light may be coming on because the battery light is on, the ABS may be detecting low voltage or something else. The ABS system itself may not have a problem.
Use a volt meter and check voltage at the battery with the engine running at 2000 RPM. Should be between 13.2 to 14.8v.

As to the new battery. if new battery was charged when you turned off the car and went dead there is a parasitic drain on the battery when the engine is off.

Does the car have an aftermarket alarm, stereo, remote door lock, etc. Is the trunk light turning off with lid closed. Sometimes the heater blower control will malfunction and allow the blower to come on with ign key off.

For parasitic battery drain issues, check for a parasitic current load using an amp meter installed between the negative battery terminal and ground cable. The internet has lots of videos and posts on checking for parasitic drain problems. This is typically done by removing a fuse(s) until the drain is gone.

The alternator could also be bad and now allowing a battery drain, ign key off.

It is normal for a car to have a very small constant current drain, something like 25ma. Each model of car has its own max drain specification.

 

Thanks for everyone ones assistance and information, it turned out to be a bad alternator and after looking at the Youtube video more that I wanted to handle. Shop replaced it on Wednesday and she is good to go. Thanks again

 

Thanks for posting back with the fix.