Battery Confusion - W204 C350

[sledlife]

Hi, I'm looking to replace the auxiliary battery in my C350 CDI BlueEfficiency (start/stop function stopped working).

I understood that the auxiliary battery for this generation is in the boot. However when I ordered a new aux battery from MB a smaller style one has arrived, whereas the one in the boot is quite large. MB are adamant this is the aux battery for my car.

After looking into it I think in my car the aux is in the engine bay, and the standard battery is in the boot, but I am hoping someone can confirm please so I know I have purchased the correct battery? Below is what I have...

New battery from MB:



Battery in my current engine bay:



Battery in my boot:

 

[alexanderfoti]

No, the engine bay battery is the aux battery and your main one is in the boot. Assuming its an estate?

 

[markjay]

The FIAMM bettery that MB gave you is exactly the same as the Auxiliary Battery in the boot of my W204 C180 Saloon (now sold).

The battery in the boot of your C350 is most certainly the main Starter Battery, and not the Auxiliary Battery.

So if the FIAMM battery from MB is not the same as the battery you have in the engine bay, then I think that the chap at the parts counter may have given you the wrong battery m

 

[merc07]

I have a C350 W204 saloon, and yes the smaller aux battery is behind the ecu under the bonnet and is exactly the same as your new one, the main battery is in the boot.

That battery contact is manky

 

[sledlife]

No, the engine bay battery is the aux battery and your main one is in the boot. Assuming its an estate?

It's a saloon

The FIAMM bettery that MB gave you is exactly the same as the Auxiliary Battery in the boot of my W204 C180 Saloon (now sold).

The battery in the boot of your C350 is most certainly the main Starter Battery, and not the Auxiliary Battery.

So if the FIAMM battery from MB is not the same as the battery you have in the engine bay, then I think that the chap at the parts counter may have given you the wrong battery m

I think the new MB one and my engine bay one are the same, will need to take the cover off to confirm part number

I have a C350 W204 saloon, and yes the smaller aux battery is behind the ecu under the bonnet and is exactly the same as your new one, the main battery is in the boot.

That battery contact is manky

It does look disgusting in that pic, but gives me hope I can clean the contact and get the battery working again perhaps

Thanks for the replies

 

[Diesel Benz]

The correct part should always be checked with the vehicle VIN. What was the part number of this battery that you got?

 

[OneForTheRoad]

Hi, I'm looking to replace the auxiliary battery in my C350 CDI BlueEfficiency (start/stop function stopped working).

I understood that the auxiliary battery for this generation is in the boot. However when I ordered a new aux battery from MB a smaller style one has arrived, whereas the one in the boot is quite large. MB are adamant this is the aux battery for my car.

After looking into it I think in my car the aux is in the engine bay, and the standard battery is in the boot, but I am hoping someone can confirm please so I know I have purchased the correct battery? Below is what I have...

New battery from MB:

View attachment 136947

Battery in my current engine bay:

View attachment 136948

Battery in my boot:

View attachment 136949

It's best to check yourself at times , the pictures on the EPC at most mb spares departments can be confusing to the operator/salesman.

A young lad at my local mb was telling me my 2004 e320 had 4 pot front calipers when I knew it had single piston Bosch for the SBC brake system. Utterly useless on this occasion.

 

[Skd884]

It's a saloon

I think the new MB one and my engine bay one are the same, will need to take the cover off to confirm part number

It does look disgusting in that pic, but gives me hope I can clean the contact and get the battery working again perhaps

Thanks for the replies

I never use stop/start

Charge your battery you might not require a new one.

 

[ToeKnee]

I guess the question is what did you ask for? If you just asked for the aux battery for your vehicle then that is what they have given you, if you asked for the battery that goes in the boot and not mentioned aux battery then they have given you the wrong one and it should be corrected by them

 

[John N]

Hi, I'm looking to replace the auxiliary battery in my C350 CDI BlueEfficiency (start/stop function stopped working).

I understood that the auxiliary battery for this generation is in the boot. However when I ordered a new aux battery from MB a smaller style one has arrived, whereas the one in the boot is quite large. MB are adamant this is the aux battery for my car.

After looking into it I think in my car the aux is in the engine bay, and the standard battery is in the boot, but I am hoping someone can confirm please so I know I have purchased the correct battery? Below is what I have...

New battery from MB:

View attachment 136947

Battery in my current engine bay:

View attachment 136948

Battery in my boot:

View attachment 136949

Unless my Eyes are deceiving me, the Battery you got from MB and the One in your Engine Bay are the same!

The only difference being the Orientation of the Positive Terminal Guard!

 

[sledlife]

Update:

I believe the small battery in my engine bay is the auxiliary. So I tried cleaning the battery terminals/connectors on the current battery but it made no difference. Swapped out the battery for the new one, but again no difference (FFS!).

Part numbers are slightly different but I think the battery is the correct one - 000 982 07 08 (old) 211 541 00 01 (new)

When I turn the car on the dash ECO button flashes on briefly then goes off. Same for the ECO logo in the drivers display. So I have no idea what the issue is. Had the car almost a year, display ECO logo has only turned green about twice ever, which is why I assumed it was a failing battery.

Any ideas where to go with this anyone? I've read main battery failing may also cause this so will see if I can get some testers on it.

 

[OneForTheRoad]

Update:

I believe the small battery in my engine bay is the auxiliary. So I tried cleaning the battery terminals/connectors on the current battery but it made no difference. Swapped out the battery for the new one, but again no difference (FFS!).

Part numbers are slightly different but I think the battery is the correct one - 000 982 07 08 (old) 211 541 00 01 (new)

When I turn the car on the dash ECO button flashes on briefly then goes off. Same for the ECO logo in the drivers display. So I have no idea what the issue is. Had the car almost a year, display ECO logo has only turned green about twice ever, which is why I assumed it was a failing battery.

Any ideas where to go with this anyone? I've read main battery failing may also cause this so will see if I can get some testers on it.

Stop start actually relies on the main to make it work. Try charging the big boot battery and see what happens.

 

[sledlife]

Stop start actually relies on the main to make it work. Try charging the big boot battery and see what happens.

Ok, just looked on the multimeter and it's saying 12.6v when car is off, and 14.7v when on, which appears in normal range. Will try and get hold of a charger to see if that does anything.

 

[Skd884]

I never use stop/start

Charge your battery you might not require a new one.

^

 

[Gazwould]

Stop start actually relies on the main to make it work. Try charging the big boot battery and see what happens.

Found the opposite with my 204 ( auxiliary in boot ) , you can remove the 7.5A fuse for the auxiliary battery or disconnect it for a temporary disable or totally remove the battery for a permanent disable .

 

[OneForTheRoad]

Found the opposite with my 204 ( auxiliary in boot ) , you can remove the 7.5A fuse for the auxiliary battery or disconnect it for a temporary disable or totally remove the battery for a permanent disable .

His aux is under the bonnet , his main is in the boot.

 

[markjay]

Update:

I believe the small battery in my engine bay is the auxiliary. So I tried cleaning the battery terminals/connectors on the current battery but it made no difference. Swapped out the battery for the new one, but again no difference (FFS!).

Part numbers are slightly different but I think the battery is the correct one - 000 982 07 08 (old) 211 541 00 01 (new)

When I turn the car on the dash ECO button flashes on briefly then goes off. Same for the ECO logo in the drivers display. So I have no idea what the issue is. Had the car almost a year, display ECO logo has only turned green about twice ever, which is why I assumed it was a failing battery.

Any ideas where to go with this anyone? I've read main battery failing may also cause this so will see if I can get some testers on it.

You did start your post with "I'm looking to replace the auxiliary battery in my C350 CDI BlueEfficiency (start/stop function stopped working)", and we responded to your question rather than offer a diagnosis....

There are many reason why Stop/Start won't work, the most common one is in fact a weak main batter (which, as we have established, in your car is in the boot). There are other potential issues, and STAR (or iCarsoft) will tell you which conditions have not been met. But I would start with measuring the voltage of the main starter battery (in the boot), with the ignition switched-off.

 

[Gazwould]

That's Eco for ya , it costs you more money than any tiny fuel saving .

There is also the wear and tear on various components .

My Eco earned me money as I sold my good auxiliary for £30 and saved 5 kg in weight .

 

[Bobmeister]

The stop start has loads of conditions for it to work such as internal temp, level surface, sufficient fuel, engine is warmed up, charge level and voltage of battery is sufficient. Needs a quality battery too, if your main battery is 7 urs old maybe replace it with a quality battery

 

[OneForTheRoad]

The stop start has loads of conditions for it to work such as internal temp, level surface, sufficient fuel, engine is warmed up, charge level and voltage of battery is sufficient. Needs a quality battery too, if your main battery is 7 urs old maybe replace it with a quality battery

I find mine works just as long as the battery is charged and the dash turns green. Other conditions just seem irrelevant .