A.M.

I have driven the car maybe once in the last month. I noticed the "Convenience Functions Disabled Due to Low Voltage" message in the dash at my last start up, went away after a few minutes of driving.

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.

Critter

Check voltage on battery under the hood, probably DOA (under 12.5V)also check battery voltage in trunk (should be 12.6V and up) car not running. Replace one or both, running voltage with good batteries should be 14.2-14.3V.
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.

A.M.

Very useful information. Your right should not ignore a warning on a benz...can lead to failure as I'm experiencing right now.

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.

Critter

Okay, how old are the batteries, anything over 5 years. REPLACE them. If you own a charger unhook the negative terminal on the trunk battery and charge the battery for minimum 4-6hours or over night if using a small charger ie 10 amp or less.

A.M.

I do not own a charger. I'm not sure how old the batteries are. Bought the car 6 months ago. Passed 2 PPI with flying color.

Critter

You there!!

Critter

Look on the batteries they should have a date on them, PPI means squat.

Critter

Date sticker is usually on one of the sides of the
battery

A.M.

Thank you very much. I'll take a look when I get home!

Critter

Any stickers with dates on them.
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.

A.M.

Well ****ty. now the trunk wont open, cant take a look at the battery.

Guess Ill be calling roadside assistance tomorrow.

Shieeeeeeet.

Rocman8

Use your blade key!

A.M.

Dont have one.

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.

Rocman8

Just making sure you know it's the little metal strip that slides into your remote and what you would attach the rest of your keys to.

A.M.

God damn noob...learning curve. lol.

A.M.

Recharge by feb of 2014 is whats on the sticker.

Toadster

fortunately you can get a new battery for relatively cheap - I found one at Sam's Club for $129

there are more expensive ones, but for $129 you get a 3 year warranty, and 2 year pro-rated after that

cetialpha5

Is that a regular flooded battery or an AGM battery at Sam's club? If it's an AGM, that's a pretty good price. I believe factory is AGM and they are supposed to last longer than flooded batteries. If OP isn't a Sam's club member, I would suggest Advance Auto, they have an AGM battery for $189 and there's a coupon code that can be used online to take off $50 (TRT30 or WD51A) so it's $139. AGM also doesn't normally vent gasses like flooded batteries so you're less likely to get corroded terminals.

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.

Elhonaz

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

Critter

So if that is true then he needs both batteries, because failure of the trunk battery will be covered by the aux battery in which is toast long ago.
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.

Toadster

The $129 is the following:
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

Toadster

the AUX battery can be had for ~$65
Aux Battery ACDelco ATX14BS (14-BS) Maintenance Free Absorbed Glass Mat (AGM) Powersport Battery $67

HeissRod

What does warranty matter if the battery is the wrong type?

Toadster

energy is energy - lead acid battery will start and run your car like an AGM one will

Elhonaz

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.