Battery dead? Help...
Couple weeks have gone by, same message pops up when I put the key in the ignition, but now the car wont turn on and a red Brake code pops up telling me I have less braking power...
Not sure if all she needs is a jump? Which If I understand has to be done with the battery in the trunk?
Pretty depressing, was going to have my res delete + cls mufflers installed this week.
Trunk battery starts the car, battery the under the hood powers the brakes.
Guys you should not neglect a warning message on a Benz, they pop up for a reason.
Probably the small battery is toast and running off the alternator which will be toast next, trying to charge that big resister that used to be a battery. Voltage regulator and or alternator would be next step.
Battery tenders are cheap and if you do not drive for months at a time are priceless, Harbour Freight sell small cheap models .75amp perfect for keep battery charged.
Hope this helps.
But what can I do today? Jump start it? Get her to the garage? Wait and buy a voltage meter? I'd really like to get her started and in proper hands.
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From your original comment, I would replace both batteries or if you have a buddy, remove both from the car and take them to Auto Zone or a place similar to get them to load test and charged for you, they will know quite quickly if they are good or toast.
When you stated the convenience functions were not available and then after you drove the car the message went out tells me that your alternator is working at least, go check the batteries.
Maybe I can swap out the aux battery with agm motorcycle one tomorrow. See if that gets the juices going.
That or have MB make me a new blade.
Oh well, its winter...Got my faithful 2.slow to get me around.
there are more expensive ones, but for $129 you get a 3 year warranty, and 2 year pro-rated after that

There are many 2 amp battery charger/maintainers out there for around $20-$30. Only thing is that at 2 amp, an 85-95amp hour battery that's half dead would take 20+ hours to recharge. A 10 amp charger would just take a few hours to get it mostly charged. I think you can also take your battery to an auto parts store and they can charge it up for you.
Not true. The small is a backup battery for the whole system in case there is a malfunction on the main system.
http://bayhas.com/mercedes/w211/cont...ct_battery.htm
Ha ha double failure, That why I like the E it is go or no go, same with the CLK.
It was my understanding that the aux was mainly for the braking system found on 55 series cars, but being a backup is news and should be changed every three years just to ensure a backup is there when your trunk battery fails.

Some owners do not even now about the firewall mounted battery let along know what it does in these cars.
There are many 2 amp battery charger/maintainers out there for around $20-$30. Only thing is that at 2 amp, an 85-95amp hour battery that's half dead would take 20+ hours to recharge. A 10 amp charger would just take a few hours to get it mostly charged. I think you can also take your battery to an auto parts store and they can charge it up for you.
Specifications
- 12 volt
- 730 CCA / 910 CA
- Exceeds OEM Specifications
- Patented Grid Design
- Solidium Weld System
- Centered Lug and Uniform Plate Thickness
- Maximum Starting Power
- Lead Acid Battery
the $189 battery is AGM
both have the same warranty
Aux Battery ACDelco ATX14BS (14-BS) Maintenance Free Absorbed Glass Mat (AGM) Powersport Battery $67
The aux battery is found on every w211 from 03 to 06, when it used the SBC braking system. In 2006 when w211 got facelift, SBC was not continued.





