Why is my battery dead? - The Unofficial BMW M5 Messageboard (m5board.com)

NachtBlau · 3rd November 2009, 21:02

The last time I drove my beast was a week ago Monday.

Last Friday, I took a road trip in my truck, and the battery was dead. My duba$$ self left the lights on the previous night. I used the M5 to jump start it, then parked the M5. The truck drove great the rest of the weekend.

This morning, I went out to start the M5 and the power was TOTALLY dead. I didnt leave any lights on and I could not find anything else so obvious. What gives?

I didnt have time to mess with it, so I decided to leave for work. Im about to leave in a few minutes to go jump start it a drive it around for 20 minutes.

felstmiester · 3rd November 2009, 21:16

Jump it, but strait away as it cranks over turn the lights on and heater on full for a few seconds to stop any surge. Don't forget to turn off what you don't need on after though.

Drive it about for 20 mins then get it home turn it off and then try it again in ten mins. Give us an update then.

NachtBlau · 3rd November 2009, 22:58

The battery was D-E-A-D!!!! I mean TOTALLY dead. I hooked up the jumpers and it took a good 20 minutes before I can start it. In fact, it took a good 10 minutes before any electronics worked.

Then I drove it around for about 30 minutes and went on some roads where I can get the RPMS up.

E55AMG2 · 3rd November 2009, 23:20

BMW batteries are pretty poor in my experience. They dont like to hold their charge when sitting around, nor do they like to be left sitting w/o a battery tender. On top of that, the car never truly shuts down...it goes into a low power standby mode. This, on it's own, kills weak batteries after just a few days of the car sitting.

My guess is that jumping the truck killed the battery and you didnt leave the M5 on long enough to recharge it adequately.

NachtBlau · 3rd November 2009, 23:27

Quote:

Originally Posted by E55AMG2

BMW batteries are pretty poor in my experience.

Hmmm. I just sold my 15 y/o E36 and it had the same battery in it from day one.

Quote:

Originally Posted by E55AMG2

My guess is that jumping the truck killed the battery and you didnt leave the M5 on long enough to recharge it adequately.

My guess as well.

Also, I must note, that I had a "CarChip" in the ODB. But I doubt those things pull any power when the car is off.

E55AMG2 · 3rd November 2009, 23:31

Quote:

Originally Posted by NachtBlau

Hmmm. I just sold my 15 y/o E36 and it had the same battery in it from day one.

My guess as well.

Also, I must note, that I had a "CarChip" in the ODB. But I doubt those things pull any power when the car is off.

OBD isnt powered when the car is off. You've also got to consider how long the car sat for before you bought it. When I bought mine (actually both of my BMWs), I had to change the battery w/in a few days of buying the car. I run Die Hard International Group 49's w/o issue, and there is a 5 year prorated warranty should I ever have one.

NachtBlau · 20th November 2009, 15:03

NachtBlau · 20th November 2009, 15:04

jclyman · 20th November 2009, 17:26

Sorry, but if you had done a search, and read some other battery posts, ALL of your questions would have been answered.

NachtBlau · 20th November 2009, 17:39