Battery weirdness... - PeachParts Mercedes-Benz Forum

bhatt · #1 01-19-2008, 09:00 AM

I have a 2 year old Interstate battery in my W140 500SEL. Never had a problem with it, but have heard these cars go through batteries quickly. It is now on it's 3rd Canadian winter.

I usually park the car in the garage, but was visiting relatives in Detroit a few weeks ago. Parked the car on the driveway and didn't drive it for 24 hours (it was 0 degrees fahrenheit, so pretty cold out!). I then started it to move it off the driveway (car ran for maybe 15-20 seconds) and shut it off. Didn't drive it for another 24 hours.

I went to start it and it would turn over but not quickly enough to catch. I cranked it for a few minutes (so there was obviously juice in the battery, just not "enough" to turn the starter fast enough). Hooked up jumper cables, waited 20 seconds, and it fired right up.

Haven't had a problem since (although it's been garaged every night since).

Recently, when I start the car after a really cold night, it throws an ASR light and goes into limp home mode. If I immediately shut it off and restart it, there is no problem for the rest of the day (even after making multiple trips)

My theory...
Battery is dying. Reserve capacity is fine, but the cranking amps are significantly reduced. Car starts with low levels of battery juice, so it throws an ASR error code. 2nd try starting the car works find (there is obviously no ASR problem) because there is enough voltage to keep the system running fine.

Do I need a new battery? Or could this be another problem like an alternator? I am assuming with the cold weather/parking outside issue, it's likely the battery but don't want to change it if not necessary.....

Help!

Thanks..