There are some good videos that show you how the standard electrics work on a Sprinter. Here’s one that opens up the distribution box on the house/starter battery.
However, many videos and blog posts assume you have a left hand drive model. Even the manual – written in UK English – assumes you have a LHD model.
I wanted to figure out how to disconnect the battery so I could safely connect a split charger. Here’s how I found the ground point from the negative terminal of the battery on our 2012 NCV model.
Remove the trim around the footwell on the passenger side. Helpfully, it’s marked with a battery icon
Remove the toolbox cover in the passenger footwell by turning a slot headed screwdriver in the plastic fastener
Unscrew the four screws holding the lower console casing in place. You’ll need to lift up the heavy floor mats to reach this. Slide the casing horizontally towards the seats.
There’s the earth point for the black cable from the negative post of the battery, on the centre console column. The battery is under the black panel in the footwell.
A closer look at the earth point
Inside the battery compartment. This is an aftermarket battery. You can just see the distribution box from the positive terminal (red cables) down on the right hand side
Andrew Sleigh 
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