Extra auxilliary FIAMM battery in boot E class ?

[kc1952]

Can anyone tell me what the little battery made by FIAMM does in the boot of my w207. 2012. I didn't know it was there until I lifted the plastic cover from it in the spare wheel well. Someone must know what it is there for. It's nothing to do with the main battery. I know that because if that's flat and the car barely starts the one in the boot doesn't seem to help. I haven't put a meter on it yet to see what condition its in, but would love to know WHY its there.

 

[Mr. B]

Can anyone tell me what the little battery made by FIAMM does in the boot of my w207. 2012. I didn't know it was there until I lifted the plastic cover from it in the spare wheel well. Someone must know what it is there for. It's nothing to do with the main battery. I know that because if that's flat and the car barely starts the one in the boot doesn't seem to help. I haven't put a meter on it yet to see what condition its in, but would love to know WHY its there.

The auxiliary battery will run things like stop / start if fitted.

 

[Mr. B]

Sorry to hijack your thread but speaking of auxiliary batteries I would like to know if you keep the main battery on trickle charge during the winter months will it also charge the auxiliary’s battery at the same time OR does the auxiliary battery need to be charged separately?

 

[mersum1es]

Sorry, wrong car... first I read this is W211, then W221

 

[Aded]

Hi all,I love to know more about this auxiliary battery as well pls.My car w204 c class got the battery as well,is it for eco only, and sometimes I turn off eco button since my mechanic said not good to be using it.

 

[merc07]

Sorry to hijack your thread but speaking of auxiliary batteries I would like to know if you keep the main battery on trickle charge during the winter months will it also charge the auxiliary’s battery at the same time OR does the auxiliary battery need to be charged separately?

No it won't charge the aux while trickle charging the main - I had the same question a couple of weeks back and went out and measured it in the end.
It will have to be done separately.
This was on a w204

 

[markjay]

The auxiliary battery runs the electrical consumers in the car while the engine is switched-off due to the Stop/Start (ECO) function, for example when stopped at traffic lights. This allows the main battery to maintain full charge so it can start the engine. If the stop is too long and the auxiliary battery voltage drops below a certain level, the engine will start itself so that auxiliary battery gets re-charged. A green ECO button means that all preconditions for Stop/Start have been met, including (but not limited to) that both the main and auxiliary batteries are sufficiently charged.

 

[Petrol Pete]

Hi KC, welcome. Have a close look at the battery , see if you can see a date code on it. If it says 2012 be prepared to buy a new one soon.

 

[Gazwould]

Hi all,I love to know more about this auxiliary battery as well pls.My car w204 c class got the battery as well,is it for eco only, and sometimes I turn off eco button since my mechanic said not good to be using it.

Today is a good day for you .

At the top of the auxiliary battery is a 7.5A fuse , remove it and it permanently disables the pesky stop strain .

 

[kc1952]

Thanks for that guys. I was clutching at straws trying to find a reason for my ongoing ACTIVE BONNET PROBLEM. Don't think its the aux battery. thanks.

 

[Angiross]

can i replace the auxilliary battery on my 212 Eclass 2014 with a motorcycle battery as they seem the same spec but loads cheaper?

 

[AMGeed]

can i replace the auxilliary battery on my 212 Eclass 2014 with a motorcycle battery as they seem the same spec but loads cheaper?

Yes. Its the same battery. 12v 12Ah

 

[Fastcar155]

Hi ,

I understand that it has been proved that Stop Start systems damage car systems./ / Started motirs

 

[Muckypaps]

Changed my starter four times in 5 years, Renew timing chain on every B service,