Mercedes-Benz Forum banner

1 - 7 of 7 Posts

·
Registered
1985 380sl - charcoal grey w/lt grey interior
Joined
·
182 Posts
Discussion Starter #1
all,

so i charged my battery last week and it registered 12.59 volts

i let the car sit for a week and today the battery showed 11.89 volts...i was able to start the car and i let it run at idle for 10 minutes.

after turning the car off i tested the battery and it shows 12.59 volts

so i assume my alternator is ok? ...and the battery is at the end of is life and needs to be changed?
 

·
Registered
W210.265/2001, W220/S500/2000, Porsche 997 C2S/2006, GMC K1500/1992
Joined
·
2,157 Posts
Your battery is weak, even it sit for a week, it should be around 12.5 to 12.35V. Anytime it drop below 12V is a warning sign.
 

·
Registered
W210.265/2001, W220/S500/2000, Porsche 997 C2S/2006, GMC K1500/1992
Joined
·
2,157 Posts
You can still use the battery til it will not start the car but do not go out of town with it.
 

·
W210 Moderator
99 E320
Joined
·
5,105 Posts
i'm going to be the gadfly and say it's not conclusive. the alternator/voltage
regular appears to be okay, however it's too soon to point to the battery as
failing. it may be just fine, but there is a drain on the battery even with the
ignition off. odds favor weak battery but that doesn't mean it needs replacing.
more sampling tests are needed.
 

·
Registered
1997 E320, 1997 S320
Joined
·
2,946 Posts
best way to find out is to unplug the battery every time the car is sitting for long time, but make sure you know the radio code. nothing can drain the battery when it's unplugged. if the voltage drops, than it's the battery. if it doesn't drop, than something else is draining it.
 

·
Banned
1999 E300 TD
Joined
·
2,045 Posts
Screw the radio code------------somewhere in the stickies a very bright guy came up with that 9V battery attachment that plugs into the cigar lighter.

I thought that was ingenious and will save loads of time resetting everything!!
 
1 - 7 of 7 Posts
Top