Won't Start after charging battery
 

Hi All

Hoping you could confirm my thoughts. Went out this morning to start the car and I had zero dashlights. Tried to start the car and wouldn't even click the solenoid. Sigh... I gave it a boost and it started right away. When I removed the negative lead from the booster cables, the engine died. Hmmmm. Started it again and same thing.

Metered the baterery and it was 11.5. Charged it and the charger said it was at 85% capacity, Charged to 100% in 10 or 15 min.... already suspicious. Same thing. No dash lights and no start. Now the battery charger said it was at 10% capacity. (WTF) Then re did the connection and it was at 65% capacity. All with the battery cables disconnected from the car. Put an ameter between the Plus post and the lead and read 0 draw on the current with key off.

I'm thinking battery, but likely an altenator as well. Thoughts?


Peter - powerless in Toronto

Check the other end of the negative cable where it mounts to the chassis. Also, check the engine ground. It's located on the passenger side motor mount arm. Clean and reattach both ends of the cables.

Thanks Cooljess76

I did check and they were fine. Finally broke down and bought a battery load tester.
At rest the battery is fine. Under load 1v. If I boost the car and let it idle for a bit i can remove the booster battery. When I put on a load it stalls the car. If I leave the booster battery on and put a load test on the charging system it falls bellow 11v or fail.

I am assuming its a alternator which took out the battery.

Sigh... Going shopping on Monday for parts.

Thanks again
Peter

You know the more I think about this. I think its the regulator (diode) that is leaking and drained the battery. Hence why its draining the battery.

Peter

Hey Peter, with the engine running, you should see close to 14v across the battery terminals and at the back of the alternator. I had a bad engine ground and was getting between 10 and 11v. It would fluctuate and slowly build up to 11.7v then drop back down to 10v. In your case, maybe the alternator is bad. You can always take it to your local auto parts store and let them bench test it. They'll be able to tell you right away which part of the alternator is failing. Anyway, hope you get things sorted out soon man. Best of luck, wish I could offer more help.

Resolved
 

Thanks to all. Just thought I would add the fix.

The ground was fine, I have double checked them both and all is good.
The voltage on the battery at rest was 12.5v.
With the key out and red battery disconnected, there as 0 amps flowing from the battery + terminal to the cable cable.
With a battery load test, the battery read 1.5v.
When I boosted the car and disconnected the boosting battery, the car stalled.
When I boosted the car and left the battery on the load test on the charging circuit fell bellow acceptable but I would expect that with a bad battery.
The battery is a BMW original about 1.5 years old.
I replaced the battery with a Napa Battery ( 6 year warranty vs BMW's 1 year warranty).
All is well since battery was replaced.

Cheers

How much voltage are you getting between the battery terminals when the car is running with the new battery? How about @ the back of the alternator? I ask because when I was having charging system issues, I was getting 10.5-11.7v. 3 batteries and 3 alternators later, I found the REAL problem. Every time I'd replace a battery, it would work fine for about 2-3 months before it would die. I was using Sears Diehard batteries which have a 10 year warranty. You should see 13.5-14v between the terminals when the engine is running. If not, then you've just put a bandaid on the problem and it will certainly haunt you later down the road. If you're not seeing 13.5-14v, I'd highly suggest actually removing both of the grounding cables(negative battery cable and main engine ground located on the passenger motor mount arm) and scrubbing the contacts with a wire brush. Who knows, maybe your old battery was the culprit. But when I visually inspected my grounds, they looked clean and tight. It wasn't until I removed the lower engine ground that I noticed some pitting where the cable must have been arcing because there was no corrosion. Best of luck to ya.

With the new battery it was 13.8v I think. I will double check when I get a moment. Likely tomorrow. I do remember checking it, just cant remember. If its light enough I will check at the alternator as well.

I did check the ground(s). They were all good. Clean and solid. Even took a jumper cable and ran it from the battery to a variety of grounds on the car (engine.. etc) Made no difference (as you would expect). Car has been great since the battery was replaced. I will keep an eye on the voltage.

Funny I never think of Sears for a battery. Don't know why.

Thanks
Peter