Rewired with 4/0 Cable and Symmetry: 10 Kilowatt Battery System in Mercedes Sprinter with dual Lithionics 400-amp batteries, dual Xantrex Freedom XC Inverter/Charger
Due to my concussion my writeup with pictures is delayed. A more detailed report to follow as time allows when I recover sufficiently to work at the computer for some time.
My new 1.5-inch-thick hickory butcherblock table is now in place. It turns out to be a very challenging issue to wire dual inverters to dual batteries and dual bus bars and fuses using 4/0 cables in a confined space; my usage constraints made it particularly challenging but other configurations might be easier. A 144-inch wheelbase Sprinter leaves little room to place both batteries along with wiring and outlets, etc, at least for my requirements with a 44 X 29 inch table and need for legroom and storage room underneath. It is not that it cannot be done, it’s that between the very thick cables and my requirement to maximum leg room and other space and where I wanted the outlets, it’s a tricky business to pre-plan all cable routing.
To my knowledge, this is the most capable battery system ever installed by ADF Sprinters (they do about 280 Sprinters a year). Or maybe ever installed in a Sprinter, period. I working both with Lithionics and ADF Sprinters to wire it as good as it can get in terms of proper electrical performance.
- The dual Xantrex Freedom XC 2000W inverter/chargers are bolted on under the hickory table, so strong and tough that care is required to not break the screws. Sorbothane is used in many places between such hard contct surfaces to allow a little give on very rough roads.
- The dual Lithionics batteries now each have a 250 amp fuses on the way to the bus bar. Negative and positive 4/0 cables to the bus bar are now identical length, which should deliver symmetric draw from each battery — to be verified soon.
Here is the cabling required:
- One 4/0 cable from positive terminal of each battery to 250 amp fuse box then to positive/hot bus bar, identical lengths for symmetry. We ended up keeping this cable length to only 5 feet.
- One 4/0 cable from negative terminal of each battery to bus bar, identical lengths for symmetry.
- Dual 1/0 cables from alternator to bus bar (for charging).
- One 1/0 cable from positive bus bar to each inverter, equal length for symmetry (4/0 not needed for ~12 inch run, besides, 4/0 lugs won’t fit into the inverter).
- One 1/0 cable from negative bus bar to each inverter.
- Dual 4/0 grounding cables of equal length from chassis to negative/grounding bus bar.
That’s a LOT of cabling! It’s not as elegant as I would have liked, but the space constraints made it tough: the 4/0 welding cable cannot just be bent to fit; one has to plan out where excess cabling length will be looped or routed for example, since the cables between the hot and ground bus bars *must* be identical for symmetric performance. Thus one cable has to be coiled, complicating matters a bit more.
Shown below, 4/0 welding cable.