Originally Posted by Car1
Open the front engine access, look down on lower, right side.
I relocated mine from under the step to the engine compartment to shorten the starter cable run and keep it from overheating while it snaked around hot metal. Created a mount such that the bottom of the battery was mounted a little high to keep the water splash down and protected from the same with a barrier. All the cranking problems vanished and the battery life was extended as well.
If you can follow the starter cable it would lead to the engine battery.
In some sprinters the thing is under the drivers feet!