Forum Discussion

1L243's avatar
1L243
Explorer II
Dec 19, 2021

Battery Bank Wire Size

I built my battery bank four 12 volt deep cycle batteries with 340 amp hours. At the time I had not added the 500 watts of solar and a 2000 watt inverter that I now have.

At the time I used 2 AWG cable between the the batteries which are wired in Parallel. The 2 AWG was a upgrade from the 4 AWG battery cables that it came with.

I'm using 4/0 cable from the inverter to the batteries. I occasionally have a high demand on the battery bank by running the microwave or a drip coffee maker. These events only last for 2 to 5 minutes at a time. When this occurs the battery voltage will drop suddenly as low as 11.8 volts due to the high demand. As soon as the demand is over the voltage recovers almost immediately to it's pre voltage level before the event.

I decided to beef up the battery cables that link the four batteries together with 2/0 cable. I could not find anything that really set the parameters for battery cable size.

I have not had a chance to try it yet but I am curious to see by
increasing the battery cable size to 2/0 if the voltage drop during a high amperage discharge will improve.

Any thoughts.
  • time2roll's avatar
    time2roll
    Nomad
    Dec 19, 2021
    Have probably moved from a bit undersized to somewhat oversized wire. Battery voltage will still sag at high draw situations. Generally I would recommend 400+ amp hours for a 2000 watt inverter. Eventually if you move to LFP batteries the voltage will hold up significantly better.
  • Skibane's avatar
    Skibane
    Explorer II
    Dec 19, 2021
    At 150 amps (approx. 1800 watts), a 5 foot run of 2 gauge (10 feet total wire length) will introduce around 0.3 volts of drop.

    So, if your fully-charged batteries have a "resting" voltage of 12.5 volts, you would expect 12.2 volts at the end of your 5 foot wire run when drawing 150 amps - and any additional drop would be due to the internal resistance of the batteries themselves.

    Going to 2/0 wire gauge under those same conditions would produce a voltage drop of 0.15 volts in the wire.

    A 0.15 volt improvement isn't much.

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