jamiem1987

Hi guys I'm new to this forum so hi and great forum....


Just a quick question regarding the battery voltage on a w220 2004 s500..


Been playing about with holding the REST button in on the climate system to view various parameters, I've noticed the battery voltage with the engine off reads low (around 11.7v after been stood over night but around 14.2v with the engine running). The engine starts fine with no hesitation and all of the electronics work fine. I've put a multimeter on the battery and with the engine off its around 12.08v which again seems low. It's a genuine Mercedes AGM 95a battery.


I'm wondering if the low voltage readings could be because of the systems that power up on the car when you open a door etc. such as the command fan running putting a draw on the battery hence the voltage reading lower than it would be without the draw> Could someone else do a check on their w220 and tell me the battery voltage?


Don't want to get stranded with a dead battery!


Thanks

fxdeebee

resting =12.34
Key on, engine not started = 12.04
Engine on = 14.12


REST button diagnostics agree with multimeter +/- .006 v

jamiem1987

brilliant thanks for that, i think there must be systems that draw a lot of power when you unlock the car that drags the voltage down, ive heard the systems on these cars can be awake for 30 mins pulling 4amps before they shut down.

Yours seems low like mine with the key on so hopefully theres not much concern. The voltage on mine doesnt drop below 10v when cranking

Thanks again