subrt.p

Hi guys, it looks like I need to fully chargé battery in my MB CDI. The question is if I have to disconnect it completely before or simply hook up to the charger. I asked local service and got answer in conflict to what is given in manual.
Thanks - Pavel

Carsy

I have done it both ways on a C220 CDI .

Safest is to disconnect.

Most important to completely remove key first to protect electrical gear.

Best to slow charge for 24 hours or so .

subrt.p

Thanks Carsy. Isn´t there a risk of loosing all stored data (radio, telephone, navigation, etc.) when I disconnect the battery?
pavel

vic viper

Using a modern electronic charger you dont need to unhook, just connect and charge.

Mike20

I have been regularly using a MB trickle charger without disconnecting the battery without any problems on my 2007 w204 C280 (3L V engine). The charger is actually made by CTECK (model XS3600) and is fully automatic. I am not sure if this charger is suitable with later models which have an additional stop/start battery and whether it charges both the batteries or just the main battery.

subrt.p

Thanks Mike,
there is realy a lot of "mysteries" concerning MB models and maybe even differencies between models for europe, USA and other countries. Do I understand it right there are two batteries in C class, CDI? Where is the second located and what it is for?
Regards

Carsy

Pavel, There is one battery in my 2007/08 220CDI. JC

Mike20

With stop/start models there are two batteries one main battery in the engine compartment and a smaller one in the boot next to the spare wheel cavity. The smaller battery works to restart the motor when the engine turns off with the stop/start system so that the main battery is preserved. Must admit I am not totally familiar with how the system works particularly at night - the headlights remain on when the engine stops (do not know what the limit of this is).

Have recently purchase a new c250 cdi which has two batteries. Not sure how the trickle charger will work on the new car ie in which sequence the two batteries are charged.

subrt.p

Mike thanks again for your explanation and good luck with your new MB. I am afraid my battery is at the end of life and simple recharge is not sufficient. I am going to také my car to local service today to see their judgement.

vic viper

Nope, the smaller battery is used as backup to sustain the car functions when the engine turns off, such as the Infotainment, blower, lights and so on. The starter motor is still powered by the main battery.

subrt.p

Thanks for explanation Vic. I only wonder if I have start/stop model. How could I reveal it?
Pavel

vic viper

If you do you should have a button in the centre console called "ECO" with a green LED

djejglk

I guess the US versions are different. I have a keyless go version and there IS an area in the trunk for a battery (you can see the outline for it), but there is no battery back there.

vic viper

The bodywork looks the same on all models, all cars have the battery recess, it would be far to costly to make different bodyparts depending on car options.

subrt.p

Pls, one more question Vic. Today I got a sad result from local MB service - battery is not sufficient for winter starts. They offer replacement (original MB part) for approx. 3 times the price of Varta Silver Dynamic (77Ah, 780A), that I can buy in specialized battery shop.
Solely disconnection and atachment of the new one looks simple and can be DiY but I am afraid of potential risks. Is the replacement safe, should I meet any precautions or better leave it to service men. To save money is very seductive but I do not want to damage something. What do you think about it.
Lots of thanks - pavel.
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vic viper

Of course there is always a risk of damages when replacing the battery but the dealer is risking the same thing when installing an original part.


To reduce risks to a minimum you should use a special device that keeps the power on while replacing the battery.

Carsy

My original OEM is a Varta Glass Matt Battery 70 amp /Hr 760 AEN .

Paying the dealer 3X the price is extortion.

If you are concerned buy the Varta from an auto electrician who can install it for you with the equipment Vic speaks of..

The main thing when installing is to remove the key totally.

I understand the W204 electrical system is much more robust than the w 203 which had problems with electrical spikes damaging SAMs.

C300fan2

For those in Canada with the W204 model.(c300 v6 sport) Mercedes part # is 000-982-32-08-m22. Dealer price 269.99$. Prefect fit compatible battery is available at Costco. Group H7 Fitment Code 22 119.99$

Easy replacement, 10 min job, no need for any special tools or knowledge.