rtlc427480 avatar image
rtlc427480 asked

Long Wire Runs to Battery From MPPT 100/15

I have looked via the search and not found a clear answer..

To save running additional wires through already crowded firewall grommets is it a no-no to use existing circuits?

This is a LandCruiser 4x4 in which there already is a Bluesea busbar for chassis ground inside the vehicle, via 4 awg marine Ancor wire. The battery in engine bay is to chassis ground via 2 awg Anchor marine wire (all lugs properly crimped).

For positive circuits to the interior there is an 8 awg (20 amp maxi fuse at the battery) to the back of the vehicle with distribution via a Blue Sea fuse box.

There is also a 4 awg marine Ancor positive wire circuit to a busbar at the back of the vehicle for an air compressor and inverter, fused with a resettable 70 amp Cooper Bussman breaker at the battery.

Both the 8awg and 4 awg runs are 12’ to 14’ runs from the battery.

What downfall would there be of running the output (battery side) 0f the MPPT 100/15 battery + connection to either of the positive circuits and using the chassis ground circuit for the battery – connection, instead of a new run (would use ancor marine 10awg if needed). The circuits are oversized for what is needed for the 100/15 so resistance and drop are minimized if I’ve figured things correct.

The solar panel positive and negative will be direct to the MPPT 100/15.

The Load side of the MPPT 100/15 will not be used.

Thanks for your thoughts and ideas.

MPPT ControllersbatteryGrounding
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1 Answer
JohnC avatar image
JohnC answered ·

Hi, If I'm reading your intentions correctly, it seems ok to me. You'd have to be careful with all your connections to make sure no high resistance spots are created, for the earth-return equally.

Under full production, say set up for the current to push one way, the V's at the batt should match those at the mppt output terminals. If they don't the mppt will be working a false V, and won't perform to expectations. Watch too for hot wires/connections.

Treating the mppt as a separate power source would be advised, so maybe an inline fuse on it's +ve outlet too.

But you seem pretty well advised and aware, so likely capable of dealing with any issues that might arise. Most of this stuff is commonsense and care. Good luck with it.

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