Auxiliary battery

[Andy 321]

Hi everyone,
Just joined the Forum and have bought a E250 AMG Coupe about a year ago and love it.
Since working from home due to lockdowns an error issue appeared Auxiliary Battery error. I have been taking the car out on essential runs and after the recent cold weather snap the error appeared. It goes away when the car is started a second time and has now recently appeared once. On reading a fault issue web site it suggested that damage could happen if the car was driven beyond a 100km distance. Spoke to Mercedes Benz who wanted to take it in and run it through a diagnostic test (£100.00 per hour but thought it would take a lot less time than an hour. The replacement battery is £98.11 + time to install it.) I don't want to pay for unnecessary work if this could be down to recent cold weather, but is it German engineering and should be weather proof as Germany has very cold winters. Can anyone think of why the error message is appearing and what I can do to fix it.

 

[sonic]

Charge the battery up & see what happens then, 7 years life is not bad for a battery.
Batteries are the same in any car when its cold, the efficacy is dramatically reduced.
Both my cars are garaged & if not used I charge them every other week.

 

[Jkh112]

I had the auxiliary battery warning on my 2014 E class last year.
I charged the aux battery (small one under the boot floor) but the error soon came back. Bought a replacement battery (from MB Grangemouth as they give a good discount). Easy to fit, no coding needed.
The error has not returned since.
Stop/start also works more regularly (this may be a good or a bad thing depending on your pint of view).
If your battery is 6 or 7 years old and is throwing up errors then probably time it was replaced.

 

[Gazwould]

Good thing or a bad thing... it's a ****ing no brainer !

 

[Andy 321]

Thank you both,
Sounds like a replacement, are there one or two auxiliary batteries. Don't want to replace the wrong one.

 

[onefortheroad]

Thank you both,
Sounds like a replacement, are there one or two auxiliary batteries. Don't want to replace the wrong one.

Just 1 in the boot , drivers side uk. Under black plastic cover.

 

[Andy 321]

Thank you. I don't do any mechanics just very basic stuff.