Changing battery W219

[mikerd4]

My car is slow to turn over on start up during the cold mornings, I was thinking of replacing the battery. Is it a simple swap out job or is removing the battery going to require the car to be hokked up to a Mercedes computer to reset everything?
Also whats the aux battery for that Ive only just discovered is fitted to the CLS?

 

[KillerHERTZ]

Test the voltage first, with key in position one, and the dash set to outside display screen hold reset which should beep.
Then leave that screen on and check voltage levels?

 

[mikerd4]

Thats not going to test cranking voltage though? Batteries fail under load especially when cold. Whats the aux battery for? Can I change the main one and not lose any settings?

 

[whitenemesis]

The AUX battery in the engine bay is a back-up for the main system battery in the boot. It will only come into play should the system voltage drop critical.

If you replace the system battery you will have to normalise windows and sunroof.

 

[KillerHERTZ]

Thats not going to test cranking voltage though? Batteries fail under load especially when cold. Whats the aux battery for? Can I change the main one and not lose any settings?

Your welcome.


Yes it will, you will see a dip in voltage as you start the car.

 

[mikerd4]

Didnt realise it would stay on as I turned the engine over thats brilliant thank you.

How do you normalise the windows? Does the aux battery maintain other settings?

 

[KillerHERTZ]

At windows lowest level, hold down for 5 secs, then raise window to highest point and hold up for 5 secs. This teaches the car the range of travel for the window.

 

[andy27168]

Hi,
Do you get the warning message "consumables switched off" when you start up? if you don,t then I would just leave it alone.
Regarding the aux battery under the bonnet passenger side under the pollen filter, if the date stamp on top of battery states its over 4 years just replace it.
If you replace the Aux. battery disconnect the rear battery first, then replace the Aux battery, and reconnect rear battery.

 

[mikerd4]

Thanks for the advice guys. I havent looked a the battery but I strongly doubt it has been replaced in the cars lifetime.

 

[mikerd4]

Got around to checking it this morning.
Battery at 11v in position 1. Drops to 9v when turning over. Jumps to 14v when running.

 

[charlieboy2608]

You may also have to reset other items like memory seats/door mirrors-not 100% sure-but just be aware of it.

 

[KillerHERTZ]

You may also have to reset other items like memory seats/door mirrors-not 100% sure-but just be aware of it.

Shouldnt need to unless the battery has discharged over a week or so.