E-Class (W212) 2010 - 2016: E 350, E 550

What is electric box next to spare tyre

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Old 03-03-2022, 02:40 PM
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W212 E Class 220D
What is electric box next to spare tyre

Hi,

When I lift the floor of my boot I see a spare wheel and to the right there is a large electric box of some sort with cables hanging out if it. Does anyone know what this is?

Thanks
Old 03-03-2022, 04:28 PM
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MY'14 W212 M276 3.5NA @60kMi
AUX...

Originally Posted by gussy81
Hi,

When I lift the floor of my boot I see a spare wheel and to the right there is a large electric box of some sort with cables hanging out if it. Does anyone know what this is?

Thanks
This I believe is your 12Volts AUX battery flanked by its SSR Mgt relay where fat cables are terminated.

Some W212 models have their MAIN batt there to keep people guessing I suppose

Having found that location, you can now conveniently charge both batteries directly from there by switching the (+) lead from one big red cable to the other.

This trick becomes handy when the MAIN is flat and you can't pop the hood open easily.

Last edited by CaliBenzDriver; 03-03-2022 at 07:40 PM.
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Old 03-03-2022, 05:13 PM
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2016 E350 4Matic wagon, 2019 Ford Expedition 4x4
Originally Posted by gussy81
Hi,

When I lift the floor of my boot I see a spare wheel and to the right there is a large electric box of some sort with cables hanging out if it. Does anyone know what this is?

Thanks

a photo of this would be helpful, as there's a number of possible things there.... the rear SAM, the HK Logic7 subwoofer, a stereo amplifier, and yes, the aux battery if you have push-to-start (if you don't, a much smaller aux battery is located under the driver side instrument panel).


this is under the rear deck of a US 2016 model E350 wagon (aka estate aka touring), the black plastic thing that says "harman/kardon" is the subwoofer, and the thing below it is the R-SAM and aux battery.



Last edited by Left Coast Geek; 03-03-2022 at 05:15 PM.
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Old 03-06-2022, 08:27 AM
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W212 E Class 220D
Originally Posted by Left Coast Geek
a photo of this would be helpful, as there's a number of possible things there.... the rear SAM, the HK Logic7 subwoofer, a stereo amplifier, and yes, the aux battery if you have push-to-start (if you don't, a much smaller aux battery is located under the driver side instrument panel).


this is under the rear deck of a US 2016 model E350 wagon (aka estate aka touring), the black plastic thing that says "harman/kardon" is the subwoofer, and the thing below it is the R-SAM and aux battery.



This is what I am referring to. Thanks
Old 03-06-2022, 09:02 AM
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Originally Posted by gussy81

This is what I am referring to. Thanks
Nothing has changed... It's your Auxiliary battery... Tons of threads about it here, some good, others not so much...
Old 03-06-2022, 09:37 AM
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1922 Ford Model T / no OBD
What country you are in?
My US E250 Bluetec doesn't have spare as they fit DEF tank in the space. So beside tank and battery on the side, I also have DEF module there.
Old 03-06-2022, 09:46 AM
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Don't listen to these guys, that's part of the missile guidance system that isn't hooked up from the factory as you have to purchase armory from your authorized weapons dealer, check your local/county guidelines for state and local regulations.
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Old 03-06-2022, 10:47 AM
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MY'14 W212 M276 3.5NA @60kMi
Baby battery boot ports...


2-In-1 port for CTEK trickle charging


Originally Posted by CaliBenzDriver
This is your 12Volts AUX battery flanked by its SSR Mgt relay where fat cables are terminated.
...
Having found that location, you can now conveniently charge both batteries directly from there by switching the (+) lead from one big red cable to the other.

This trick becomes handy when the MAIN is flat and you can't pop the hood open easily.
Your car uses 2x batteries. The Main battery up front does the important work and may benefit from CTEK maintenance.

Take your time to search this forum for tons of existing knowledge.



Last edited by CaliBenzDriver; 03-06-2022 at 02:22 PM.
Old 03-06-2022, 11:52 AM
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1922 Ford Model T / no OBD
Originally Posted by hyperion667
Don't listen to these guys, that's part of the missile guidance system that isn't hooked up from the factory as you have to purchase armory from your authorized weapons dealer, check your local/county guidelines for state and local regulations.
DARN, the salesman lied to me that this operate passenger ejection seat.
Old 03-06-2022, 01:54 PM
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W212 E Class 220D
Originally Posted by DFWdude
Nothing has changed... It's your Auxiliary battery... Tons of threads about it here, some good, others not so much...
Originally Posted by kajtek1
What country you are in?
My US E250 Bluetec doesn't have spare as they fit DEF tank in the space. So beside tank and battery on the side, I also have DEF module there.
I am located in Ireland. Car imported from UK

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