W205 Auxillary battery charging.

[Aneshkrza]

Need some advice. My start stop in my W205 2016, hasn't worked. I recently fully charged my main battery. Do I need to charge the auxiliary battery? If yes, how do I change it ?

 

[OneForTheRoad]

Agm battery charger.

 

[fourwheels]

Mine frequently doesn't work. I'm just not doing enough driving under current restrictions for the car itself to fully recharge battery.
I trickle charge with a CTEK charger once in a while. S/S usually works then for a day or so before stopping again. Never seen the need to charge aux battery, even if you can. Others may know better.

 

[wongl]

Need some advice. My start stop in my W205 2016, hasn't worked. I recently fully charged my main battery. Do I need to charge the auxiliary battery? If yes, how do I change it ?

The Aux Battery on the W205 should be a capacitor, and when an error message is displayed on the dash, this will need to be replaced. Replacing it without the warning message is unlikely to improve matters.

If your W205 is not starting/stopping, chances are your main battery will need to be replaced. But only replace the main battery after you have eliminated all other causes.

 

[geoffus]

When my start/stop stopped working I left my main battery on charge overnight, next day the start/stop would work OK again.
Couple of days later it stopped again, the car was also sluggish to start when outside was very cold. In the end I fitted a new battery and now everything works perfectly again. If your Aux battery is low you will have a Auxiliary Battery Malfunction warning on the dash and IF it is a battery it can be charged like a motorcycle battery,

 

[John]

The Aux Battery on the W205 should be a capacitor, and when an error message is displayed on the dash, this will need to be replaced. Replacing it without the warning message is unlikely to improve matters.

If your W205 is not starting/stopping, chances are your main battery will need to be replaced. But only replace the main battery after you have eliminated all other causes.

They seemed to have changed from traditional battery to capacitor in 2016/2017 it looks like so it might be a battery.

@OP - If it has the aux battery, I would charge it fully and see what condition it is in after that.

After 5 years, it might be shot but you won't know until you try. You should replace main and aux batteries at the same time really.

If it is a cap, I would replace it personally as I've read they can be troublesome.

This was my previous post on it - with how to find the aux battery if it does have one.

Where is auxiliary battery in w213 E220d located? | Parts, Maintenance & Servicing

This will show you where the battery is and you just need access to the terminals to charge it like you would imagine.

I wired in a couple of wires on to my aux battery so I can charge it through the fuse hatch at the rear.

If your aux battery has never been charged, it may take a while to fully charge but it's a small battery so we are talking an hour or two at a guess.

My aux battery gets a charge once every quarter now and takes a few moments to fully charge now (and also it was new a year ago).

That will sort the stop/start.

 

[mikrt]

You'd do well to invest in an Icarsoft, not just for this issue, but any others which may pop up.
It will tell you which parameter/s aren't being met, preventing stop - start occurring.

 

[Gazwould]

The car fixed itself , why ruin it .

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[wongl]

I wired in a couple of wires on to my aux battery so I can charge it through the fuse hatch at the rear.

My aux battery gets a charge once every quarter now and takes a few moments to fully charge now (and also it was new a year ago).

I have done the same by fitting a set of CTEK quick connectors to my Aux Battery and giving it an all-day charge once a month while it is parked in the indoor parking lot at work.