W212 Aux battery malfunction

theworkerb

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Dec 13, 2019
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London
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E63 AMG
Hey guys,
So I get this error message on the first time that I start the car. Subsequent starts are fine. I bought a battery charger and charged the main battery and still saw the error the next morning. I then met a friend and placed the charger on the aux battery and after a couple of minutes the light indicated that it was fully charged. I then placed the charger back on the main battery and it started charging again and didn’t indicate fully charged before I took it off charge as I had to run some errands. Should the main battery discharge that quickly? Could that message display even if the fault isn’t actually with the battery?
 

Riva811

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CL500 Blueefficiency
if the error keeps coming up after the car has been off for a while then its the battery
 
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theworkerb

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E63 AMG
The main battery or the aux?

would isoft or similar provide further detail?
 

Riva811

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828
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London
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CL500 Blueefficiency
The main battery or the aux?

would isoft or similar provide further detail?
it will provide the same error potentially. if you leave the car off for 8-12 hours and then set your key to position 2 and use isoft to check battery voltages it might come up with something. I prefer doing it with the voltometer. If the voltage is under 12.6V then best to replace it.
 
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theworkerb

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So aux battery was 12.8 this morning and the front battery is 12.2. Based on your advice it’s the front that would need replacing?
 

AMGeed

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2014 E63 Biturbo
Do new batteries need to be registered/coded?
No. Just a straight swap.
Maybe the windows and pano' roof will need resetting.

I'd say the original battery needs replacing. Its done well to last 7 years.

Make a note of the Part # on the battery and get a quote from a Mercedes commercial dealer. Cheaper than the car main dealers by a long way.
 

E55BOF

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Not the local MB commercial dealer I tried.

If you connect either a battery trickle charger or another 12V battery to the car's connector terminals before you unbolt them, you won't lose any of your settings.
 
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theworkerb

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Thanks for the replies fellas, will start looking around for quotes. Mercedes commercial seller?
 

KillerHERTZ

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Easy to swap over yourself, I have created a guide here:


ECP + First time discount and it wont cost you much.
 

Benz2fast4u

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Jan 28, 2013
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L
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E320 CDI V6
Hey guys,
So I get this error message on the first time that I start the car. Subsequent starts are fine. I bought a battery charger and charged the main battery and still saw the error the next morning. I then met a friend and placed the charger on the aux battery and after a couple of minutes the light indicated that it was fully charged. I then placed the charger back on the main battery and it started charging again and didn’t indicate fully charged before I took it off charge as I had to run some errands. Should the main battery discharge that quickly? Could that message display even if the fault isn’t actually with the battery?
Hi, just out of interest, what does the error message say?
 
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theworkerb

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E63 AMG
Easy to swap over yourself, I have created a guide here:


ECP + First time discount and it wont cost you much.
I’ve watched that, great vid as always. At the moment I’m thinking of getting one from Mercedes, this one lasted 7 years which is impressive
 

E55BOF

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Battery Megastore (on eBay as batterymegauk)) is excellent - they supplied the correct OE Varta for my CLS, next day delivery if ordered by 16:00, cheaper than Tayna.
 

Crispian22

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Mar 12, 2021
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Warwickshire
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Ml63 amg performance pack
I replaced my aux battery in my ML last week,got a new one from Merc,just over £100,which i didn't think was too bad a price.

I didn't have a warning on the dash,the reason I changed it was,
A,It was coming up for 7 years old.

B,every now and again, the drivers door didn't lock/unlock,I figured it was either the lock solenoid on its way out,or possibly low voltage from the battery, the battery was easier(and cheaper) to change and has fixed the problem!
 

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