GRAFH

Does this mean their is a problem with one of my batteries or just a general service warning???????????

JeffyPooh

It means it's 76°F. ;-)

Battery or alternator or something related.

GRAFH

Oh snap. I'm hoping it's just low voltage in one of the batteries. It went away after driving awhile. The car sat a while with out being started so may have just got low.

MercFiveHundred

I got the same message. I didnt drive it for about a week. Went shopping for stuff and no problems and no error messages. I think it's just that it sat or the rear battery will need replacing soon.

gaazmon

it will come back again. probably the aux battery in the engine compartment. gonna change mine soon.

andreholl

I had to replace my aux battery under the hood when I got that warning.

squerly

Batteries will suffer damage when discharged beyond 25% of their storage capacity. At 50% they have suffered greatly. Not a good idea to let them get to this stage of discharge unless you have enough disposible income to replace the batt's. I keep a battery tender on mine when it going to sit undriven for any amount of time.

dmpc06

On which battery does one put the tender the one in the trunk or the one under the hood?

vettdvr

Let it sit overnight do a volt check on the aux bat if less than 12.0 V change it.

squerly

I wouldn't think it matters as the charger should feed both batteries simultaneously.

GRAFH

So I fixed it by topping of the 6 cells with distilled water and slapping a trickle charger on it over night. Started up the next day and it didn't come on. Fyi each cell needed 2/3 cup water to top off. Make sure the drain tube is attached properly because when on the trickle charger some may boil over.

edwinwalke

What kind of battery do you have in the car. Quite uncommon to have to add water to a battery these days.

Diesel Benz

No it does not work that way, there is an isolation relay that opens when the ignition is switched off (also at other times but that is not relevant here).

Diesel Benz

It should not be common on a W211, these are supposed to come from the factory with AGM (sealed) batteries. If you open the cap, the battery is gone. Perhaps the cars you refer have the AGM battery replaced with an ordinary one (which is not good).

squerly

I thought about that when I posted, but figured if there was one that somebody would jump in. Thank you DB, I stand corrected. So apairently he will have to put a tender on both of the batteries to get the desired results?

lkchris

WTF? RTFM

vettdvr

Water? mine is a gell cell battery and I never add water. Where did the water go? Heat drives the water out if it is a conventional battery. An internal high resistance will also generate heat and cause the water to evaporate. You have a heat source causing the water to boil out.

I think you will still need a battery. But what do I a know anyway. ??

GRAFH

Stock Mercedes battery made in Spain. I may have added a little too much water that's why a little drained out of the drain tube when it was on the charger. No return of the "workshop light" so far and the battery seems fine.

willy_manilly

Not sure if this has been stated above as i CBF reading.

But check the SBC Aux battery under the hood, when thats about to fail that CHECK BATTERY warning light comes on, and if that batterys low, it will drain and cause errors on the 2nd battery in the boot.

GRAFH

Where is it under the hood?

GRAFH

Wow a few of you guys must not wrench on your own rides, one of you is in Europe so that may be the reason why you have a water less battery. Here are a few pics of both of my stock batteries. Both require distilled water. I topped them both off, gave them full charges on the trickle charger and all is well now. No need to buy a battery quite yet.





Also be sure to clean up the battery posts and inside the terminals with one of those battery post brushes before reconnecting. FYI the main battery in the trunk took 3 days to be fully charged with the trickle charger. I don't like the idea of having the aux battery (water) right under the cabin filter. If it sulfates those fumes will be sucked right in to the cabin lol. Going to try and find an optima type that will fit there.

stockC43

The battery is the same glass mat style battery as a optima. optima's are just wound in stead of flat panels. the mb batteries are sealed so no worries of any fumes. your best bet is a oem battery to keep the light off

GRAFH

Wow, did you read this thread? Or look at the photos? It's obvious from the photos that the stock batteries are not sealed and require water. Also I stated I topped both batteries off with water. Also I don't need new batteries since I fixed the problem with water and a trickle charger.

JeffyPooh

It might be a case of YMMV.

The big battery in the trunk of my car is more-or-less sealed. I think that it might (?) have caps under the big battery top decals, but it's obviously intended to be maintenance-free. Adding water, assuming it's possible, would make the battery in my car extremely ugly - with torn off decals.

The last time I added water to a car battery would have been in the 1970s.

GRAFH

WOW Do you see the 6 white caps on top of the white battery? Those are the caps for the cells. They unscrew with a butter knife. Doesn't get an easier and you won't mess up any stickers The aux battery just has one large strip cap that comes off with a small screwdriver.