Z4-forum.com

I'm writing this to alert you guys with new cars that aren't driven that much. Also, I'd like to have your opions as to what I should do,

My Z4 has 9400 miles after 18 months use. Car didn't start the other day and AAA jump charged the battery. AAA said I should replace the battery. Also had another tech check battery and he said that it seemed OK and needs to be recharged. The indicator eye on the battery is a black color, indicating that the battery needs recharging, but it isn't yellow=replace battery. Anyway, I called my friendly SA at BMW and he told me that the battery wasn't under warranty because I didn't drive the car enough to keep the battery properly recharged. He said that I had to do over 10k miles/yr for the warranty to be in effect. Called BMWNA, and they verified.

What exactly did BMW NA verify?

Is it just with the newer models? Mine is 2003 with 16K miles on it and I didn't drive it for almost two weeks and it cranked right up. What's the deal?

fire-n-ice wrote:Is it just with the newer models? Mine is 2003 with 16K miles on it and I didn't drive it for almost two weeks and it cranked right up. What's the deal?

Batteries are fickle things.

I don't know if what I'm about to say is true with the newer batteries and cars.

I was always told that when a battery goes flat ( not charged ), the car alternator does not have the ability to charge the battery in full.( black indication ) I was told to charge the battery and the car would then be able to keep the battery charged at that point, assuming the car is driven. The car alternator just does not generate enough amperage to charge the battery completely. I'm really surprised that BMW would not charge the battery correctly for you or even to tell you to charge the battery completely.

With the battery showing black there is most likely nothing wrong with the battery other than it needs a complete charge.

IMHO

20ducks wrote:What exactly did BMW NA verify?

That due to my limited use of the car, the battery was not being properly charged and that the warranty is therefore voided.

IMZ4N wrote:I don't know if what I'm about to say is true with the newer batteries and cars.

I was always told that when a battery goes flat ( not charged ), the car alternator does not have the ability to charge the battery in full.( black indication ) I was told to charge the battery and the car would then be able to keep the battery charged at that point, assuming the car is driven. The car alternator just does not generate enough amperage to charge the battery completely. I'm really surprised that BMW would not charge the battery correctly for you or even to tell you to charge the battery completely.

With the battery showing black there is most likely nothing wrong with the battery other than it needs a complete charge.

IMHO

Reasonable information, agrees with what others have told me. I now have the Battery Tender Plus on order.

I have a 2005, and during a major cold spell this past winter the battery lost enough juice to keep it from turning over, although the dome/dash lights still worked.

I bought a new battery tender on eBay for around 55 shipped. It's convenient, you just plug it into the DC outlet, instead of having to clamp it onto a terminal lead. It did the job over the winter, and I haven't needed it in the spring/summer, even when the car hasn't been driven for a week or two.

I would also agree with IMZ4N. Even after a long drive the alternator does not charge the battery 100%. Afterwards, If I hook up the tender, it will still show it's charging for 8-10 hours after I plugged it in.

friend had the same problem 1 mth ago. battery went flat and they did not warranty it but couldnt get on z4um to find that post about the warranty

I don't drive the Z very often so I also use a drop charger. It's simulating a normal battery use process. They sell for around 50euro's or about 45 USD, it's a good investment . I use such a charger on my moto's to.

IMZ4N wrote: . . . I was always told that when a battery goes flat ( not charged ), the car alternator does not have the ability to charge the battery in full. . . . The car alternator just does not generate enough amperage to charge the battery completely.

Not true. The alternator has plenty amperage to charge a fully discharged battery. The problem is that when a battery discharges too much it produces sulfate crystals which adhere to the lead plates and reduces the available power that the battery can produce. This basically kills the battery.

Deep cycling=battery death.

Useful bit of info about batteries...
http://www.edmunds.com/ownership/techce ... ticle.html