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2016 B Class CDI180
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Discussion Starter · #1 ·
Hi,
I'm in UK and having problems with intermittent stop-start function in my B Class cd180. It is almost certainly due to low mileage (13,000 in 3 years).Having read all the posts I am pretty sure that the auxillary battery needs charging but I cannot find it. I have seen the main battery under bonnet and the tiny 1.2AHC which is under the trim in the passenger footwell but cannot find the Auxillary 12v 12 AHC Gel battery that powers the Stop Start. The car is still under guarantee but I don't want to sit in a MB dealer (1 hr away) for 2 hours while they charge the battery. I know what I am looking for but cannot find the location. Several sites have been discussed (under passenger footwell) but I can only see the 1.2 AHC battery and fuses under there. Also "under the boot" has been mentioned. Can anyone point me in the right direction please?
 

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2016 B Class CDI180
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Discussion Starter · #3 ·
Auxiliary battery location.

Hi,
I have checked the 2 hatches either side of the boot (trunk). However, I have seen 2 quite wide ridges running front to rear in the trunk with plastic covers and they look similar to an E Class auxiliary battery replacement video on YouTube. I will have to pull the plastic plugs and investigate. Very puzzling. Thanks for the suggestion.
 

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2016 B Class CDI180
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Discussion Starter · #4 ·
I have checked the 2 ribs running through the trunk with no joy. I checked the main battery and the voltage seemed a little low at 12.2v so I charged the battery. It has an 80 AHC AGM battery which seems more than adequate for a 1461cc Diesel engine so maybe they have cut out the stop-start auxillary battery and just kept the small 1.2 AHC for accessories and the main one under the bonnet doing normal starting and Stop/Start.
I am due a long run in 2 days so I will see if the amber stop-start symbol turns green again. Otherwise I will report it to MB as a fault. I am aware that AGM batteries cannot be charged with normal battery chargers. I used a CTEK with an AGM setting. It came up a treat.
 

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2006 W245.232 | 2012 W246.243 | 2013 W176.043
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162 Posts
Hi many

do u managed to find the aux battery?

its under the front passenger foot rest. u need to pull down the carpet and floor panel. then u will see some plastics covers. the battery is under the plastic covers which u need to unhook it from the slot.

follow the red wire and u will see the battery, a bit tricky but u can do it.
 

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2016 B Class CDI180
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Discussion Starter · #6 ·
Battery still not found but stop/start working again.

Hi Hafiez,
Thank you for your suggestion. Could you please be more specific? In the uk the passenger side is on the Left as you face forward. In countries that drive on the right it is on the right. I have examined the uk passenger footwell closely and by pulling back the carpet can only see a fuse box and the tiny 12v 1.2 abc battery which is not the one I am looking for. Other posts show it is the size of a motorcycle battery.

Today I drove a total of 200 miles in the vehicle. After 180 miles the stop-start began to function correctly. I am not sure if it was because the auxiliary battery was now charged or because I braked really hard to avoid an idiot, and there is a loose connection.

I will call in the MB dealers and report it as a fault under warranty.

Thanks.
 

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2006 W245.232 | 2012 W246.243 | 2013 W176.043
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162 Posts
yes, im using the same car. u have to look at the passenger side foot rest.
that 12v tiny battery is the aux battery. it has negative and positive terminal right?

https://www.benzworld.org/forums/w246-b-class/2833809-w246-diy-remove-install-either-battery.html

view this link, other member already posted before.

as for the an event stop start began, I think that because your battery has loose connection with the cable. I have the same problem as you last month. the battery suddenly work after sudden brake. upon checking, yes the connection cable loose with the battery. IMO, this battery is seldom gives problem and no need to replace it. just check the connection. after I tightened the cable, my car start-stop works as it should. this fix no need for u to go to the workshop. u can do it by yourself.
 

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2016 B Class CDI180
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Discussion Starter · #8 ·
Still cannot locate Stop/Start Battery

Hi Hafiez,
I have been under the passenger footwell again and the stop start battery cannot be seen. The plastic cover is for the fuse box and no other battery is visible apart from the tiny auxillary battery and it is very small with push on connectors. This battery is definitely not the stop/start battery as the wires are too small to start the car. Visible is a brown (positive) thick cable which disappears into the central console and looks like it may be the size of a starter lead. As the car is still under warranty I do not want to strip all the carpets out looking for it. MB must have made it accessible if its life is only 4-5 years.

If you google MB B Class 246 stop start battery you will see a motorcycle size battery which is 150x90x45mm and this is what I am looking for. The MB instructions you sent me (I have seen already) mention removing the bolts in the additional battery terminal and the tiny battery has push on terminals.

I may have confused you with the model. It is a 2016 W246 B 180 SE D Auto, I took the description from the last MB service sheet which was wrong. If I could work out how to post a photo on here I would send you a clear photo. Different MB models with Stop start seem to hide the battery(ies) under seats, Floors, trunk, side panels, I just cannot find mine!
 

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2016 B Class CDI180
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Discussion Starter · #9 ·
Hi Hafiez,
I have been under the passenger footwell again and the stop start battery cannot be seen. The plastic cover is for the fuse box and no other battery is visible apart from the tiny auxillary battery and it is very small with push on connectors. This battery is definitely not the stop/start battery as the wires are too small to start the car. Visible is a brown (positive) thick cable which disappears into the central console and looks like it may be the size of a starter lead. As the car is still under warranty I do not want to strip all the carpets out looking for it. MB must have made it accessible if its life is only 4-5 years.

If you google MB B Class 246 stop start battery you will see a motorcycle size battery which is 150x90x45mm and this is what I am looking for. The MB instructions you sent me (I have seen already) mention removing the bolts in the additional battery terminal and the tiny battery has push on terminals.

I may have confused you with the model. It is a 2016 W246 B 180 SE D Auto, I took the description from the last MB service sheet which was wrong. If I could work out how to post a photo on here I would send you a clear photo. Different MB models with Stop start seem to hide the battery(ies) under seats, Floors, trunk, side panels, I just cannot find mine!
Having spotted that all recent MB cars have a QR Code (Marked Rescue Card) on the Drivers door pillar, I scanned it. It did indeed show a diagram which listed Fuel tank, airbag and other major components. Both Batteries were listed as: On-board electrical system Battery and Additional battery for ECO Start-stop.


Though the diagram (shown looking down on the car) shows the steering wheel on the Left (on my car it is on the right) it shows the position of the large main battery to be under the hood on the left (looking forward) which is correct for my model. However, it shows Battery number2 (additional Battery for ECO Start/Stop as being on the opposite side to the main battery just to the right and below the centre video screen. A side view shows this second battery as being in line (at 2 O'clock) to the wheel hubcap, under the footwell. I have found the tiny 1.2 AHC battery in the passenger footwell (above the fuse panel in photo) but no joy with the other battery which measures 150x90x45mm.

Despite having the "treasure" map, I still cannot find the battery location. Interpreting the diagram, it would be where the foot pedals are located. I have removed the only cover in that area and pulled up the carpets as best I can. On the passenger side, unless it is buried under the fuse box panel I cannot see it or any cover that might be hiding it. I have seen other photos that show a stout red wire leading to it but I cannot see any such wire leading to it.


Trying not to get fixated with this but having spent 4 years as a vehicle mechanic and rebuilding 6 classic motorcycles from the ground up, it should not be impossible for me to find this da**ned battery. Photos attached.
 

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2006 W245.232 | 2012 W246.243 | 2013 W176.043
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this how its look under my carpet.

sorry I don't know how to rotate it...


I wonder why yours look different.

is it because facelift and pre-facelift...?
 

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2016 B Class CDI180
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Discussion Starter · #11 ·
Still cannot locate Stop/Start Battery

Hafiez,

Thank you so much for posting these. I clearly have a slightly different model to you but these photos are very helpful. They tell me I have not gone crazy!

I am going to call in to the MB dealer tomorrow and ask him where the battery is hiding. I will let you know the result.
Manny
 

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2004 Mercedes S350
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21 Posts
Any news ??? I’m also having a hard time finding that battery....the little battery i think is the alarm/siren battery...
 

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2004 Mercedes S350
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Finally I’ve figure it ou what was preventing the start/stop from kicking in....internal resistance of main battery, the ecu will check internal resistance and if not lower enough it’ll disable the start/stop, even though the car cranks up very well and strong.....so if you want to disable the start/stop, change your main battery for a smaller capacity one or for one that is not in a very good condition....lol
 

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First and foremost - thank you to all who posted in this thread. It has been most informative and useful. Like all, I have a problem with my W246 start/stop that works well for a bit after visiting the service and gradually degrades to a point where it no longer functions (orange light all the time, never kicking in).

Following your kind instructions, I was able to find the location - only to be shocked by the puny little excuse of a battery found there (see image attached)
2612413


1.2Ah ??? ARE YOU KIDDING ME??? Most of you have quoted 12Ah, online I could find some 13Ah batteries (Varta) fitting the same form factor but ONE-POINT-TWO Ah???

OK, OK, OK (breathing in a paper bag). How do I best approach this? I would like to upgrade to proper 13Ah but notice this will call for replacement of the plastic cradle, so it can be fitted in the first place. Has anyone undergone similar disappointment and successfully walked out on the other side? Any links and tips are most welcome.

Thank you for the great forum and any advice you might have.
 

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B250 2013 Sport Jupiter Red, Honda 2018 CR-V Touring, Dark Blue
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Hi, why do you want to upgrade, the MB spec for this battery is only 1.2Ah, not 13 Ah?
 

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Hi, why do you want to upgrade, the MB spec for this battery is only 1.2Ah, not 13 Ah?
Odd enough, most manuals refer to it as a 12Ah - I am desperately searching a way out of this mess, where every year I pay $200 for a new battery because something is off - it either does not charge properly, or retain charge properly, or I don't know what. Surely does not serve the purpose of keeping the start/stop alive.

I am not an electrical engineer or expert - just searching for a bazooka to take that proverbial fly off my radar.

The manual for DIY replacement shows a much bigger (size and capacity) battery than the one I posted... Like this document, posted higher in the thread (https://www.benzworld.org/attachments/w246-r-i-additional-battery-g1-13-pdf.2180865/ )
 

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W163 W202 W203 W246 MB100D
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hello, reviving this months old thread, anyone having luck on keeping the eco start stop working?

I recently changed the main battery on my W246 (size DIN88) - took days of driving before it went back to life but did not work long enough (5mins) or on some days never.

I then changed the small battery (same spec but not MB original - $20 vs $120) and it worked longer 10mins maybe but then again inconsistent, sometimes 30mins, in some cases, a quick 2 min drive is enough to enable it but then disappears. I am aware there are many parameters that enable this system (engine temp, cabin temp, seatbelt etc etc and most of all battery charge I think). I noticed sometimes it gets enabled when I switch off the A/C so electrical load must be a factor too!

This doesn't always work and I don't really see a pattern! to be honest its ok for me and I guess for many others too
I will probably switch it off anyway if it keeps getting enabled

just curious if anyone has found a definite solution to always keep it working (green icon to show ECO enabled)
The internet is full of complaints about this.

thanks!
 

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B250 2013 Sport Jupiter Red, Honda 2018 CR-V Touring, Dark Blue
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Mine has been working consistently since changing out the thermostat, and also an MB brand small battery in the passenger footwell few years ago, and the ECO light does come on frequently on the dashboard near speedometer

what year is your car? Is your car showing any codes?
 

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W163 W202 W203 W246 MB100D
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nice! great its working ok for you.
ours is a 2015, january built. no codes...
if that's the case, I might try and put back the original MB aux batt (tests seem to indicate its fine) or try to get a new one from dealer

what thermostat was changed? (where abouts in the car?) thanks.
 
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