S212 E350 Stop start not working

[costacor]

Hi all. Longtime lurker first time poster

So my 2012 S212 E350 which has always been serviced by MB under the service plan but is not doing the stop/start thing anymore.

I used the secret menu to check out battery condition and it states 12V engine off and 14.5V when engine on

Battery never been changed, so would I be correct in thinking it’s the battery that’s probably causing the issue? How do you find out the status of the aux battery? Shall I just change the battery? No visual indications anything is amiss

Other than that, never had an issue with the car in all the years I have had, save for rear air suspension. Lovely motor

 

[onefortheroad]

Charge the main until it says 12.7 v or near enough. Usually 24 hours on a smart charger . See if things improve. Also maybe charge the small aux ,check dates ,maybe time for both ?

 

[costacor]

Thanks dude. Neither battery being changed in my ownership and that’s 8 years now . I’m surprised they have lasted this long . Would it be just better to change both? Is the aux battery change a simple Kwik fit job?

 

[malcolm E53 AMG]

If the main battery is the original you are doing well I changed mine a couple of years ago.

I’m in the process of ordering a new auxiliary battery before it causes problems

 

[onefortheroad]

Thanks dude. Neither battery being changed in my ownership and that’s 8 years now . I’m surprised they have lasted this long . Would it be just better to change both? Is the aux battery change a simple Kwik fit job?

I'd imagine so. I changed mine myself .

 

[Gazwould]

Stop Strain not working is cause for celebration

My 2011 battery has very similar readings and is starting the engine no problem and that was 1.5 years ago .

 

[tpn]

My stop start stopped working some time ago and it was a failing main battery. 11.85 at the battery. You need to check at the battery as other components will be taking some power.
I never use the stop start, but I do like to know why it is not working.

Unfortunately my main battery dropped to the stage where it failed to turn the engine and took out the A/C Module

 

[ajlsl600]

And where was the protection to avoid that happening.
My understanding, stop start u avail during regen?