I recently got this volvo and the battery died shortly after. I thought it was just an old battery because it wouldnt even stay running after a jump. I replaced the battery and about 3 weeks later now it died on the way home today. I jump it and it stays running but will not start after it's shut off.. I'm charging the battery now. It's at about 30% when i started charging.
I Need help to figure out what the problem is.
The alternator was just replaced before i got the car so i believe he had the same problem.

I havent yet opened the Chiltons to see what it says that's my next step. I guess from now on I will be disconnecting the ground when I'm not driving but I have a bad feeling it is draining while I drive.. Please help.. This car's electrical is ready to give up but the motor wants to keep going.. I need the car to stay with me at least another 6 months.
I did test the alternator and it seems like it's working (Positive lead on the positive lead ont he ALT negative to chassis, measured about 12-13 volts at idle).

If anyone has any ideas on anything I can test please just shout it out.
I was thinking voltage regulator but i have no idea where it is, how to test it or If that could even cause this problem...

[EDIT]
Charged battery and now it's running again.
Sometimes the dash lights (Battery, Park brake, brake, Light-out, wiper fluid and service) stay on while driving. Sometimes they don't MAybe that has something to do with it?

 

I broght the car to autozone. They hooked their little machine to the battery and the battery tested fine as it should.. But the alt is only putting out 30 amps (opposed to the 80 it should).Although the volts were good... Should I replace the alt or could this be a problem elsewhere?

 

I had a poblem with my 88 740. I took the alternator off and it benchtested at autozone just fine. just when it was on the car it wasnt putting out a good charge. all the wiring in the back of the alternator I stripped off the plastic covering, cut off the old connectors and put new ones on and that solved the problem. I think the wires were corroded but with the covering it was hard to see it.