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View Full Version : New battery damaged if discharged within a week?


charlene8603
05-17-2010, 02:38 PM
First the question, then the backstory: if something goes wrong in a car's electrical system to cause a brand new battery to die within a few days, is the battery "as good as new" when it's recharged? My BMW dealer says yes, but I'm suspicious.

The backstory: I have a 2007 535i with about 60,000 miles on it. Just prior to the battery dying, the clock kept re-setting each time I turned off the engine. After the car was towed to the dealer, I asked the SA to look into the broader issue, but he didn't and said it was a simple matter of replacing the battery (at over $500!). This time, I am forcing them to run proper diagnostics. In going through various forums I found a technical bulletin from BMW advising dealers that, in fact, it's only in rare instances that replacing the battery solves the problem.

That leads to question #2: does anyone know if that might ALSO mean that I didn't have to have the battery replaced? In other words, not only did they not address the causal factor, but additionally they probably replaced a part that didn't have to be replaced?

For those who believe the solution is managing the drain on the battery by regularly driving long distances, locking the car at night to force it into sleep mode, and so forth (things I've read at various forums): while those things may help, the issue for me is that I haven't needed to do any of them for the last three years that I've had the car.

Any light you can shed on those two questions would be appreciated. Thanks.

w5lx
05-18-2010, 07:00 AM
For those who believe the solution is managing the drain on the battery by regularly driving long distances, locking the car at night to force it into sleep mode, and so forth....Any light you can shed on those two questions would be appreciated. Thanks.

I don't lock either one of my cars at night and they both enter sleep mode after about 10-15 minutes. I don't think you have to lock the car to force it into sleep mode......someone please correct me if I am wrong. What I do however, is to store the CA module far away from the garage to keep it from interrogating the entry system which would eventually run down the battery.

HPIA4v2
05-19-2010, 06:47 AM
First the question, then the backstory: if something goes wrong in a car's electrical system to cause a brand new battery to die within a few days, is the battery "as good as new" when it's recharged? My BMW dealer says yes, but I'm suspicious.

The backstory: I have a 2007 535i with about 60,000 miles on it. Just prior to the battery dying, the clock kept re-setting each time I turned off the engine. After the car was towed to the dealer, I asked the SA to look into the broader issue, but he didn't and said it was a simple matter of replacing the battery (at over $500!). This time, I am forcing them to run proper diagnostics. In going through various forums I found a technical bulletin from BMW advising dealers that, in fact, it's only in rare instances that replacing the battery solves the problem.

That leads to question #2: does anyone know if that might ALSO mean that I didn't have to have the battery replaced? In other words, not only did they not address the causal factor, but additionally they probably replaced a part that didn't have to be replaced?

For those who believe the solution is managing the drain on the battery by regularly driving long distances, locking the car at night to force it into sleep mode, and so forth (things I've read at various forums): while those things may help, the issue for me is that I haven't needed to do any of them for the last three years that I've had the car.

Any light you can shed on those two questions would be appreciated. Thanks.
1)it's as good as new, but the lifetime is reduced (it'll die sooner than typical 6-7 years).
2)If you never had problem in the first 3 years and no electrical problem, you may have defective battery.

cac3a
05-19-2010, 07:21 AM
I just had that problem recently.
Two ways to track it:
1.Check the voltage on batter every couple days and see if it stays the same. If you have some electrical problems, most likely they will slowly drain it again
2. Get the old battery, charge it out of the car for 24 hours and check if it picks full charge & keeps it.

I had someone do that(1&2) for me as i though I had other problems then the battery. My 545 was acting funky on the old battery, clock would die, increased emissions warning would come, cd memory wasn't working, steering wheel wouldn't stay in my settings. It was driving me nuts, then the battery died, I got new one ($465) and everything is working fine. My battery was 5 years old, so it was time for it....

I'll add one more thing regarding not oem batteries before you try to save some $$$, which I learned on my car. Battery is just a battery, one would think that if its within BMW manufacturing specs, should work the same way. Well, I had an Interstate, battery put in(registered it and everything that dealer would do) for half the cost of the dealer and we found that voltage on the alternator was bouncing up and down between by 2 volts. It can move up to .2v! So I took it to the dealer to get my alternator fixed, they said eeeeehhhh you don't have oem bat and not oem bats can cause voltage to bounce. I didn't believe in this and told them to put oem battery,which they did and said that there was no problems with my alternator. Didn't believe in this either cause I saw the meter originally bouncing and battery is just a battery in my mind. I took the car to the original shop where we saw the bouncing voltage, checked again and it wasn't bouncing anymore. The mechanic has been working on bmw's for 20 years and was surprised too...

beden1
05-19-2010, 02:41 PM
Car batteries are not deep cycle like boat batteries, and are not designed to become fully discharged. Your battery should be replaced by the dealer as it's life has been severely shortened. But, the computer system will re-set in your BMW if the battery is down to 20%, which is not totally discharged. You should check the battery status with a tester.

We lock our '08 535xi and our battery charge seems to last longer. I also have to maintain the battery with a tender if it's not driven more than 2 days.

BMW has not fixed this issue, which they should more than saying the cars are not driven enough. We don't have any problems with our non-BMW cars.