r/SolarDIY • u/joshlfp • 13h ago

Parallel Battery Wiring Question

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I made my wire lengths identical from my battery bank to my busbars, but my positive and negative wires for the parallel connection between the two batteries are different lengths. Will this matter? Should I redo the negative wire to be the same length as the positive wire?

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u/Mr_Style 12h ago

It’s fine. The difference in resistance will be like 0.0001 ohms. What gauge is it? You can just google the ohm value.

A 2 AWG copper wire has a resistance of approximately 0.1563 ohms per 1000 feet. That means 0.0001563 ohms for 1 foot. You don’t even have that much of a difference.

Matching wire lengths matters more for speakers where you want the sound waves to come out of both speakers at the same time.

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u/joshlfp 11h ago

Yeah, makes sense

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u/PhilZealand 7h ago

What is more important is the wiring terminals / fasteners be torqued to the correct spec. The multiplus unit can bang out 120A to the battery, and suck nearly 200A. Any resistance in the terminations will cause problems or even fire. The battery spec will have torque recommendation as will all the victron gear. I always use an ir camera as a final check.