W222 - Stupid question....where is the battery !!?

CDK1

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Greetings,
Purchased the 2014 W222 S400 Hybrid L SE Line last year.
Beautiful vehicle one of the best S classes I've had - and I've had four S classes, starting from the 1998 S350 Limo which was built like a tank.

Anyway, recently I went away for a few weeks and after about 10 days I got a text from 'Mercedes Me':
"The starter battery charge status of vehicle ……. is critical. If you have any questions, please call 0800 1 7777777."
I managed to get my son to go round and switch the car on for a while and all seemed to be well.

That got me thinking - where is the battery?.
There was nothing in the manual, but there is a section about a how to disconnect the electrical system in an emergency - and in that sketch it shows the 12v battery in the boot. It looked like it was behind the back seats in the forward part of the boot.
But when I empty the boot, take off the felting, etc, I found the cut-off switch on the right, and looking towards the back seats expected to see the battery - but found a solid metal bulkhead there. So where is the battery?
Any advice would be appreciated.
Regards
CK
 

mercmancdi

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If not below cover under bonnet I would have thought it was under all the boot covers , but you were in there . Beats me.
Not the same but maybe a clue.

Both the main batter and the auxiliary batterywithin a 2015 S550 are located within the trunk. The main battery is located under the carpeted panel at the very rear center of the trunk. The auxiliary battery is located behind the passenger side panel of the trunk.
 

bembo449

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The 221 has plenty of plastic covers so i assume the 222 has even more ? Follow the wiring pal , the thickest cable under any bonnet is usually the starter cable from the battery :D
 

Wighty

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Could it be under the rear seats ?
 

bembo449

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owts possible Wighty but I reckon as its the starter one it will defo be under the bonnet ?
 
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CDK1

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Thanks guys - helped by a technically minded friend, and in his garage as weather was wet & freezing, finally found it!
It is mounted on a metal frame in a compartment behind the backrest of the rear seats.
It is approachable from the boot by removing the carpet trim in the boot behind the rear seat, behind this is a metal bulkhead which can be unbolted to reveal the compartment. In there are a number of electronic (presume) control units, including the starter battery on the left and a suitcase sized Hybrid battery on the right.
Warning - be VERY careful - possibility of high currents in there - you don't want to blow any circuits (expensive), start a fire or injure yourself.
Whilst in there, I decided to replace the starter battery originally put in during manufacture in Sept 2014 which had been triggering the 'Mercedes.Me' warning messages.

I will try to post a picture as soon as I can.
CK


BTW, to stop the battery low messages, I had purchased a solar panel which can be left on the top of the dashboard and connected to the EOBD socket. This helped keep the weak battery charged on weekends and whilst I was away on later trips.
There are a number on sale at Halfords and on line. Just make sure it comes with the EOBD connector as on some you only get the old fashioned battery spring clips or have to buy the EOBD connector separately.
"AA 5060114614185 Solar-Powered Car Battery Charger"
https://www.amazon.co.uk/gp/product/B00AC1LLQY/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

You MUST disconnect it before you switch on or start the car.
 
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