W203 - 2003 model How to charge the battery

[colin_d]

Ok, its been a while since ive used a bettery charger, (10 years), and with all the modern electronics, is it ok to simply disconnect the battery to charge, or is it ok to charge whilst connected to the car? Last time was on an ols Audi and I lost the radio code.....!

 

[jud149]

Ok, its been a while since ive used a bettery charger, (10 years), and with all the modern electronics, is it ok to simply disconnect the battery to charge, or is it ok to charge whilst connected to the car? Last time was on an ols Audi and I lost the radio code.....!

I would disconnect the battery by removing the the negative cable. You'll probably need to resynchronize the ESP, the windows, and the sliding/pop up roof after reconnect. Check your owners manual for instructions if necessary.

 

[Chrishazle]

I'd think twice about disconnecting the battery on a W203, but you also have to think about putting a big voltage surge through the SAM's - you need either an electrical guru on here or Television on "the other side" (forums.mercedesclub.org.uk).
If your battery charger has a "slow charge" setting I'd think about using that with the battery connected, so you don't mess anything up.

 

[Classy6]

It's perfectly fine to disconnect the battery & charge it. If trickle charging batteries over night, they only typically draw a small amount of current, so it's not like you are putting loads of amps to start it - not that I've ever had a problem with boost starting Mercedes either.

Charging can also be done through the body using the positive post & a chassis ground - although for maximum efficiency I would recommend charging directly onto the battery terminals - whilst disconnected.

Disconnect the negative first, then the positive. Once disconnected you should have ample room to leave it in place & charge it, or if you want it's a 13mm IIRC to remove the battery to take it out the car.

On re-connection - as above, the most you will have to do on re-connection is set your clock, reset your windows, steering angle sensor & sunroof if applicable.

 

[m7m]

I have disconnected the battery of my E-class a few times and charged it outside the car. The only thing I needed to reset was the radio code.

Didn't know that the windows need resetting. How do you reset them?

 

[Chrishazle]

Read this.

203 Battery Change Procedure - Mercedes-Benz Owners' Forums

 

[Classy6]

I have disconnected the battery of my E-class a few times and charged it outside the car. The only thing I needed to reset was the radio code.

Didn't know that the windows need resetting. How do you reset them?

It only needs resetting if you have one touch up + down functions on the switch - you most likely will. After disconnection of the battery, you will find the one touch UP function doesn't actually work because it needs to be reset.

With the window switch, send the window down on one touch function about half way. Next send the window back UP using the one touch function again but KEEP HOLDING IT - hold it until the window is fully closed, then a few seconds after you should hear a relay click - you can't always hear it click but if you've kept it held down long enough then your one touch UP function should work again. Repeat for all 4 windows.