Allen

My car is 3.5 years old. In the first 2 years, it was driven about 35,000 miles. Since then, it has been driven about 1 hour every 2 or 3 weeks...and now has 40,000 miles. So when the car began it's "not being driven" phase...I bought a Deltran Battery Maintainer, and the car stays on that all the time.

Well this morning, I press the START button, and the engine doesn't turn over at all. Lots of lights come ON while I am pressing the button, but go OFF when I release. Also, the seat bolsters VERY slowly squeeze inward when the button is being pressed. There are no fault messages showing and no problems apparent. It really seems like the battery is just dead. My question is...why did the battery go dead when is stays on that maintainer? I use the exact same model maintainer on another car ('97 911), that battery is now 10 years old, and it cranked fine, even after sitting unplugged for 3 weeks. All indication lights on the maintainer are showing "normal"...ie: just like the other car.

Is there something "special" about these cars / batteries that they don't "like" or respond to maintainers? Again, the maintainer inidication lights work exactly as they should. Any idea?

Gilgorm

I don't recall ever seeing this problem on any forums.
I suggest you try a full blown charger on the battery although it could be toast. If it doesn't charge then it is time for a new battery.
Unfortunately, comparing your 97 to an 08 is like comparing an old computer to a new one. The electronics in newer cars are significantly more complex (especially BMWs) compared to your 911.
That said, the maintainer should have done its job unless the battery was just too far gone.
Can you jump start the car? I had a 93 MB with a bad alternator and once jump started the car would only drive a few miles before the electronic ignition failed and the entire car shut down at highway speed because the battery was totally fried.
Good luck.

Allen

I called the dealer and they said it is covered under the factory warranty...expires 12/2012. So I'm gonna try to jump it off this afternoon and drive it to the dealer. If it won't jump off...I'll have BMW come pick it up.

I am kinda puzzled why the maintainer "let" the battery die...if that is in fact the case; which I think it is. I mean the car went on the maintainer within days of stopping the 100+ miles per day driving...so the battery SHOULD have been in excellent shape at that time. I dunno...I too have never heard of anything like this.

Rizbel

Bad batteries will not properly charge even with the best charger. Prolonged state of low/empty charge will destroy a battery by becoming sulfated, it can no longer hold a charge.

luigi524td

+1 Resuscitation after death ... even with a good battery maintainer properly connected (under-hood post + ground) some batteries once turned to vegetative state will have no hope of quality of life required by volt-hungry BMWs

Allen

Any ideas as to why / how the battery got dead? It was driven for 2 years, 100+ miles a day at least 5 days a week since new...that's a wonderful life if you're a battery...it should have been in great shape. THEN...it was put on the maintainer. I guess my point is that the battery should have been in great shape when it went on the maintainer. I can certainly understand that a battery on it's last leg (almost dead) would die even if was hooked to a maintainer...but that SHOULD have not been the case. Thanks for the responses....just trying to understand what happened.

gotabyte

I don't have faith in that driving profile stuff. If you were taking the car out for < 10 minutes a day and not giving it enough time to recharge that would be one thing but the alternator can easily replace what it took to start the car in a short period. The batteries they are supplying are defective. Their lifespan seems to be about 3 years on average from what I was told and that is pretty early.

Gilgorm

Regarding battery life, my 08 535i is on its second battery since I've owned it and it only has 28,800km (17,900mi).
I only fully charged the original battery once (after two weeks in the body shop it was stone dead) but the current battery has a warranty for two more years (replaced in April with only 2 weeks left on original 4 yr vehicle warranty).
I would guess that batteries of forum member cars average three years.
Even my key fob batteries have only lasted a year (replaced under warranty). LOL
GL at the dealer.