Just replaced W204 battery and things are not well.

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Broosta

New Member
Joined
May 29, 2018
Messages
18
Location
Norfolk
Car
Mercedes C250 CDI AMG Sport Edition
I was having strange issues - stop/start option vanished, sometimes (3%? of the time) won't start due to ignition not fully er ignitioning?
My independent garage said it was the battery going - car still on original battery after 11yrs! This garage is quite a way off and I last went there about 6 months ago or more.
I got a few quotes and none were under £200 for battery replacement so I got one (Bosch S5 A11 AGM) and did it myself in about 10 mins for £167. Nothing needed resetting - windows good, trip mileage the same, no warning lights.

Now I seem to have lost the Navi maps from command - not the end of the world as it was useless anyway but still.
The music on the hard drive is not always able to play, and the USB music is intermittent but the SD card music is fine as is the radio.
Command sometimes hangs on the start screen - sometimes I can press the radio button and it goes to radio but not always.
Also the stop/start is still not there - does show in yellow on turning the key without starting engine though.

I did reset the stereo system several times by holding the button down before changing the battery as it was doing it before too. And a lot of the stuff above was going on before I replaced the battery but not all.

I have heard some people say the car ECU needs to be told the battery is a new one with a full charge rather that the old not fully charged one but I've also heard many more people say nothing needs doing.

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Qs.
1) do I need to take the car to somewhere to have the ECU told it's a new battery?
2) is that stuff all due to the same problem?
3) there is only 1 battery in my car(2014 w204 estate C250 CDI with stop/start)?
Many thanks in advance!
 
Looks like you have replaced with the correct battery.
I did mine myself and had no problems and didn’t need resetting or telling the car it was new. Are you sure you don’t have an auxiliary battery in the boot ?
Scan the door QR code and it will tell you if you do and where it is.
 
I did have to get a reset done on mine, i replaced the consumer battery in the boot just to be safe and MB used the STAR system to do the necessary .... Obviously mine is a lot older and not the same model so you may have something different going on??
 
Looks like you have replaced with the correct battery.
I did mine myself and had no problems and didn’t need resetting or telling the car it was new. Are you sure you don’t have an auxiliary battery in the boot ?
Scan the door QR code and it will tell you if you do and where it is.
Thanks, yeah I just scanned the QR code in the passenger door which I think does indicate a 'stop/start' battey in the driver side of boot.
I'm not sure what to do about that now though. I never did get any actual battery warning messages coming up. I might just run it for a bit and hope the big main battery charges the auxilliary one to some extent and improves things before replacing the auxilliar battery as that looks a bit more involved to access it.
 
The W204 facelift certainly has two lead-acid batteries, one in the boot and the other in the engine bay.

On some models the battery in the boot is the auxiliary (stop/start) battery, on other models the battery in the boot is the (main) starter battery.

You need to measure the voltage of each battery first thing in the morning before switching the ignition on. If the voltage is below ~12v, than the battery isn't doing well (or there's a parasitic drain somewhere). However, unfortunately this doesn't work the other way around, i.e. a healthy voltage isn't proof that the battery being in good condition overall.

But checking the battery voltage with the ignition off should be your first step (both batteries).
 
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Thanks, yeah I just scanned the QR code in the passenger door which I think does indicate a 'stop/start' battey in the driver side of boot.
I'm not sure what to do about that now though. I never did get any actual battery warning messages coming up. I might just run it for a bit and hope the big main battery charges the auxilliary one to some extent and improves things before replacing the auxilliar battery as that looks a bit more involved to access it.

The auxiliary battery in the boot is under a black plastic cowling inside the spare wheel well, on the right-hand side.

Also, on the W204, there's no error message on the dash for failed auxiliary battery (unlike the W205, where ther is).
 
Check this out on Youtube to see how you can carry out a reset .
I have been googling the net looking for such info for a few days now but without finding anything conclusive, which is why I'm now posting on here. I've only found info on how to reset the windows and sunroof and how to do a command reset in command and the steering wheel - all which I have done and it hasn't helped so far.
I even found out how to get into the command engineering menu (press [hang-up] + [1] + [#] together) which I did but can't see a setting to change which would help.
 
The W204 facelift certainly has two lead-acid batteries, one in the boot and the other in the engine bay.

On some models the battery in the boot is the auxiliary (stop/start) battery, on other models the battery in the boot is the (main) starter battery.

You need to measure the voltage of each battery first thing in the morning before switching the ignition on. If the voltage is below ~12v, than the battery isn't doing well (or there's a parasitic drain somewhere). However, unfortunately this doesn't work the other way around, i.e. a healthy voltage isn't proof that the battery being in good condition overall.

But checking the battery voltage with the ignition off should be your first step (both batteries).
I found the auxilliary battery in the boot and measured the voltage (whilst connected) which was 13.57 V - before having started the engine since yesterday. The other main battery is brand new so I didn't measure that.
Should I disconnect the auxilliary battery? Will the main new battery be constantly giving the auxilliary some voltage whilst they are both connected to the car?
I did measure the old battery just now (disconnected to anything) which was 13.0 V, so not sure what that tells us but anyway.
 
I just disconnected the aux battrey and tested the voltage - same as when connected (13.5V).
 
Just because you have a brand new main battery, that doesn't necessarily mean that it's without a fault. If it had been sitting around for a while before you bought it, it could be "sulfated". Sulfation is less likely with an AGM battery, but it can happen. If it is sulphated, it's not going to recover just from getting charged in the car. Some battery chargers can recover sulfation. You can check for possible sulfation: any voltage less than 12.6 volts for an AGM battery indicates that your battery is undercharged. And that's possibly the result of sulfation, but not guaranteed!

If the voltage is below 12.6 volts, my recommendation would be to report it to where you bought the battery and get it exchanged.
 
Just because you have a brand new main battery, that doesn't necessarily mean that it's without a fault. If it had been sitting around for a while before you bought it, it could be "sulfated". Sulfation is less likely with an AGM battery, but it can happen. If it is sulphated, it's not going to recover just from getting charged in the car. Some battery chargers can recover sulfation. You can check for possible sulfation: any voltage less than 12.6 volts for an AGM battery indicates that your battery is undercharged. And that's possibly the result of sulfation, but not guaranteed!

If the voltage is below 12.6 volts, my recommendation would be to report it to where you bought the battery and get it exchanged.
Hi, thanks, I just checked the new battery and it's 13.5ish V, so presume that means it's probably ok?

Also I just filled the fuel tank as it was low (on reserve) and drove around for about 45 mins with much of it being 'spirited'.
Initially nothing changed (during the drive) but then I unplugged the USB stick and the SD card and eventually command would play from the hard drive.
Still no stop/start happening though, yet.
 
Try charging the aux battery overnight, you may find it will work perfectly for a day or two then revert back to failing.
Mine is the same year as yours and hasn't worked for years, I always turned stop start off anyway.
 
Try charging the aux battery overnight, you may find it will work perfectly for a day or two then revert back to failing.
Mine is the same year as yours and hasn't worked for years, I always turned stop start off anyway.
Unfortunately I don't have a battery charger!
But TBH I'm the same as you - I always turned it off asap when it was working, which was over a year ago now.
And it's more that I want it all to be working as normal to indicate there are no faults anywhere - then I'd turn stop/start off but it would be my choice rather than because something's wrong and I don't know what!

I'm going to see how it goes over the next few days and if it gets better then obviously thats a win! But if it gets worse (as in command/USB/SD doesn't work properly) then I might pull the fuse out as that's the only thing I haven't tried yet that I've heard might help (other than go to a garage or Mercedes!).
And if everything except stop/start works then I think I'll replace the aux battery.
 
Your auxiliary battery has had the same life has your main battery. Mine didn’t give me any warnings that it was knackered.
The voltage reading was the same as yours. It’s also responsible for your audio system.
It’s the cheapest of the two batteries.
 
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Everyone should have a battery charger surely.
12V/6Amp Car Battery Charger, Smart Fully Automatic Battery Charger with Temperature Compensation for Most Types of Lead Acid Batteries https://amzn.eu/d/bq5X6vy
 

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Everyone should have a battery charger surely.
12V/6Amp Car Battery Charger, Smart Fully Automatic Battery Charger with Temperature Compensation for Most Types of Lead Acid Batteries https://amzn.eu/d/bq5X6vy
Well maybe!
I thought I'd left those days behind when I used to have old hot hatches with old parts in them but now I feel like I've moved up the ranks a bit and have cars with newer superior electronics and if I get a battery that's having issues and is 11 years old I'll simply replace it.
I mean I'm not Shmee and don't have loads of cars sitting around that don't get driven enough so I don't have the same problems.
I know most of the car youtubers have CTEK chargers (too much £s for me).
And I've just been googling a bunch of chargers to the extent that I would be wary of the one you linked to - no name chinese brand with no reviews. Even the CTEK ones have some iffy reviews which put me off so any lesser brand is even more of a gamble I'd think.

I was considering getting a battery tester though - TOPDON BT200 https://www.amazon.co.uk/gp/product/B08H8DT2MF/ref=ox_sc_act_image_1?smid=A35JGKY8F8YGPG&psc=1 but I'm going round in circles with this! Not sure what to do!

The charger I'd been considering - NOCO Genius 10UK https://www.amazon.co.uk/gp/product/B0828H7PNP/ref=ox_sc_act_title_2?smid=A3P5ROKL5A1OLE&psc=1 but now looks a lot of money since it might just mean I need to buy a new battery, and then I'd not need either item for at least another 5 years if the last 5 is anything to go on!

 
Buy one from LIDL ! They cost around £15 and work very well ..... Had mine for years
 
Buy a battery, you won’t need a charger then.
If you drive it you won’t have to use a trickle charger.
 
I actually went ahead and got the battery tester I linked to above.

I tested:-
1) the old battery that I took out - 77% charged but only 22% health, so did need replacing.
2) the new main battery - 100% charged and 100% health, so I'm happy that is as I hoped and expected.
3) the aux battery in the boot - 100% charged and 100% health (also should be 170CCA but is 240CCA), which I was surprised about but happy as it was also the original 11 year old battery.

So now that I've driven the car a few days with the new battery the stereo is 100% working as it should and the starting motor seems to turn more briskly.
The only negative (or is it a positive?!) is that the stop/start is still not kicking in. And I'm merely curious about that rather than worried, as I'd turn it off whenever it was on anyway.
 

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