Aux battery information

[Danthenewbie]

I know i know this question is always floating about but i can never find the exact answers im after so ive come to everyone with my questions.

i have a 2014 w204 and recently the ECO word on the speedo has vanished and the ECO button also is not illuminated.
Start/stop only worked for a little while after i brought it but now its stopped completely and like i say the ECO word on speedo has vanished and also the HOLD brake has stopped showing and working as well.
My questions to you all are, without going direct to MB and paying loads does anyone know where else the batteries are available from ie link to websites etc. My second question is could the SS stop working if the main battery (under bonnet one) is on its way out as well? Have heard there is also another small battery under dash but wasnt sure if this was just rubbish.
Thanks in advance for any reply, your input is appreciated.

 

[Gazwould]

Main battery .

A 5 year rebranded Yuasa 115 AGM for £113 is favourable .

204 aux is in the boot .

 

[robin.large]

ECO not showing very likely auxiliary. They last around 6 years. But MB are very fussy about both batteries.
Halfords can check both for you!

Sent from my ONEPLUS A5010 using Tapatalk

 

[Blobcat]

ECO not showing very likely auxiliary. They last around 6 years. But MB are very fussy about both batteries.
Halfords can check both for you!

Sent from my ONEPLUS A5010 using Tapatalk

Please don’t go near Halfords for any battery related problems.
Unless you want them to blow up your cars electronics...

 

[malcolm E53 AMG]

Tanya online are very good put your vehicle details into their search engine but do check it against what you’ve got in the car I always buy OEM Varta batteries

 

[Gazwould]

ECO not showing very likely auxiliary. They last around 6 years. But MB are very fussy about both batteries.
Halfords can check both for you!

Sent from my ONEPLUS A5010 using Tapatalk

It's main as it's also affecting brake HOLD , on a 204 aux has nothing to do with brake HOLD , I should know because I've the aux battery totally removed .

 

[onefortheroad]

Please don’t go near Halfords for any battery related problems.
Unless you want them to blow up your cars electronics...

The recent 115 agm battery i bought at halfords ,they said over the phone ,sorry we can't fit your battery due to covid 19... in my best polite phone voice I said oh its no bother really ,I'm sure ill manage.

 

[Tony Dyson]

https://www.tayna.co.uk/car-batteries/varta/f21/ This is the same as you'll get at Mercedes but with a 4 Year guarantee MB only give you three.
Have you checked your batteries, are you sure they need replacing?

 

[onefortheroad]

3 year warranty £125

https://www.ebay.co.uk/itm/Exide-EK...533914?hash=item3431118fda:g:tSIAAOSwu4xe42Ci

 

[AMGeed]

If the battery is the original, make a note of the part number and get a quote from your local Mercedes commercial dealer.
Chances are it will be the same as the Mercedes main car dealer at a vastly reduced price.

 

[Danthenewbie]

Thank you for the replies everyone. Ive not had the batteries checked for power outage.
Only asked about the main battery as last few weeks the car has struggled to start.
What is the power suppose to be of main battery and aux battery when running and not running does anyone know.
Sorry if these are stupid questions just use to driving french cars that dont have any sort of luxury lol

 

[Tony Dyson]

12.6v is the optimum voltage of a battery without the engine running and c14.8 with.

 

[sonic]

Problem is cold weather & reduced driving due to Covid, the battery is not getting enough charge.
Buy a charger/conditioner about £15-20 at Aldi put it on charge every other week. Apart from being charged, it will dramatically increase your battery life. My E class battery is almost 10 years old, the wife SLK battery died at 9.5 years.

 

[Danthenewbie]

Cheers for everyones replies youve been really helpfull.

 

[jimbg]

 

[Danthenewbie]

Checked on multimeter today and aux battery is fine however main battery was no good,put new battery on and went for a drive and with 30 seconds stop/start was working and HOLD was also working.
Thank you for everyones input as it has helped out.

 

[Gazwould]

Now you can disable the start strain wrecking ball .

 

[Chudleigh Cannon]

Jumping on this thread with a similar problem.

used W204 C Class diesel estate bought last week aware of ECO not showing green so haggled for discount for price of new battery.

ECO switch showing green but ECO display on dash only yellow (even after several long drives)

Checked main battery, OK at 12.7 V dormant and 14V running

Went to check Aux battery and live terminal came off in my hand when unclipping cover (see photo), severely corroded. tested battery 11.3V so basically dead but I guess just enough juice/connection to power switch/display but not stop/start?

Ordered new Varta battery from Tayna, arrive today so went to fit (see photo)

First thing I noticed was the new battery doesn't have a breather tube like the old one (original MB).

Connected battery, start engine, still no green ECO switch and no ECO display at all on dash.

Tested Aux battery 12.9V dormant and 14 V when engine running so taking a charge.

Questions....

what next?

would the lack of a breather tube stop it working? does anyone have a non-breather battery fitted and working OK?

Could it be a fuse? where is the fuse for the stop/start on a W204 estate (2013)

I know some people have disabled the Aux permanently but i'm not keen to drive it with 'electrical issues'

It looks like the Varta will be going back to the shop, any recommendations for a replacement aux battery, with breather?

Help!

 

[Gazwould]

Could be the brake vacuum sensor but you need diagnostic for that .

And what 'electrical issues' will you have ?

Fix it !

 

[Chudleigh Cannon]

brake vacuum sensor? connected to aux battery? how would that affect stop/start connections?
with the old battery it was at least 'connected' now nothing.

electrical issues? having a +/- cable in the boot not connected to anything ?

the driving in do in rural Devon i'm unlikely to make much use of the stop/start and I can always turn it off at the flick of a switch, but i'd rather everything was 'working'