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Old 06-16-2019, 06:25 PM   #1
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Battery Cable for Inverter

Is 2/0 sufficient to run 10' from the inverter to the battery box?

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Old 06-16-2019, 08:56 PM   #2
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Is 2/0 sufficient to run 10' from the inverter to the battery box?


What’s the load/inverter? Usually 2/0 welding cable is a pretty safe choice, but it’s worth running the numbers on before you commit.

The closer the better though, no matter the cable size. At 12V the loss for big loads adds up fast.
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Old 06-16-2019, 09:23 PM   #3
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Yah, a 300W inverter charging a laptop is very different from a 3kW one fully loaded using an electric galley and doing laundry aboard.

Download Circuit Wizard from BSS website, make sure to use the circuit's round-trip distance, both wires, use a 1% voltage drop and round up.
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Old 06-16-2019, 09:50 PM   #4
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What’s the load/inverter? Usually 2/0 welding cable is a pretty safe choice, but it’s worth running the numbers on before you commit.

The closer the better though, no matter the cable size. At 12V the loss for big loads adds up fast.
The house inverter will be within 2', the battery bank will also supply the garage inverter (3500/7000). It will power 2 receptacles and the overhead light, occasional tools.
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Old 06-16-2019, 09:50 PM   #5
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Is 2/0 sufficient to run 10' from the inverter to the battery box?

I think its better to run from each of your batteries to a positive bus bar co-located with the inverter. Then add a DC breaker to each run for the maximum amperage you want to see per run. Even if you use 2 or 4 AWG it shouldn't matter. If your breakers trip, you should either upgrade your wires and breakers, or add more batteries with more runs. And you should always get breakers sized to trip well before your cables get hot.



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Old 06-16-2019, 09:54 PM   #6
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Definitely planned on having a shut off for the garage when not being used. I'll mark that on my electric board.
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Old 06-16-2019, 10:01 PM   #7
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The house inverter will be within 2', the battery bank will also supply the garage inverter (3500/7000). It will power 2 receptacles and the overhead light, occasional tools.


Pretty big numbers. Probably worth doing the math on it. Looking at 300/600 amps.
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Old 06-16-2019, 11:15 PM   #8
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The number of receptacles, even the size of the inverters are not in themselves all that relevant.

For any given circuit, what is the maximum amps current rate that will be drawn at any one time by the various possible combinations of load devices running concurrently?

And which of those devices are sensitive to voltage drop, what % V drop are you willing to accept on that circuit?

The above might mean #6 AWG is OK for safety, but over a long enough distance, holding to a target V drop of only 1% may require a #2 wire.
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Old 06-16-2019, 11:24 PM   #9
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My question was based on the fact I couldn't find the 10' of 4/0 wire I bought, searched for an hour couldn't find it. Then thought for a moment and realized I had used it to put a longer cord on my PC oven to move it over. So no 4/0. but I have 50' each of black and red 2/0.
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Old 06-17-2019, 08:20 AM   #10
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Might check out McMaster Carr welding cable.
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Old 06-17-2019, 10:30 AM   #11
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Welding cable is not tinned, so best avoided if any connections are exposed to the elements.

UL 1426 fine stranded marine grade is what I use
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Old 06-17-2019, 10:31 AM   #12
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My question was based on the fact I couldn't find the 10' of 4/0 wire I bought, searched for an hour couldn't find it. Then thought for a moment and realized I had used it to put a longer cord on my PC oven to move it over. So no 4/0. but I have 50' each of black and red 2/0.


If you don’t mind terminating more cables you can double it up.
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Old 06-17-2019, 12:22 PM   #13
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The number of receptacles, even the size of the inverters are not in themselves all that relevant.

For any given circuit, what is the maximum amps current rate that will be drawn at any one time by the various possible combinations of load devices running concurrently?

And which of those devices are sensitive to voltage drop, what % V drop are you willing to accept on that circuit?

The above might mean #6 AWG is OK for safety, but over a long enough distance, holding to a target V drop of only 1% may require a #2 wire.


For what wattage and run? If my understanding is even close to correct 10’ of #2 would be quite problematic at 300 amps.
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Old 06-17-2019, 12:41 PM   #14
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There is no need to guess, not a matter of opinion,

just download Blue Sea's Circuit Wizard, or use one of the hundreds of alternative references

and look it up based on objective data
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Old 06-17-2019, 02:20 PM   #15
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For what wattage and run? If my understanding is even close to correct 10’ of #2 would be quite problematic at 300 amps.

That is my understanding also David, 100 amps at most.


Good catch!


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Old 06-20-2019, 02:27 PM   #16
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I don't think sizing your battery bank cabling based on the anticipated combination of loads you're planning on running is the best practice. Sizing the battery bank itself, sure. But why would you not size the wiring based on the peak current the inverter is capable of pulling (which would in most cases be roughly double the continuous rating)?

Power demands and needs can change, calculations can be in error, etc. But the inverter's only going to pull so much power (outside a malfunction / short).
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Old 06-20-2019, 02:45 PM   #17
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Well in my case loads run through inverters is way less than 5% of the total, they are nearly irrelevant.
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Old 06-20-2019, 05:25 PM   #18
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The last time I bought 4/0 welding cable from eBay it was only about $4 a foot, US made CCI Royal/Excelene, decent quality, and free shipping.

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Old 06-22-2019, 10:26 PM   #19
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I would find a voltage drop calculater (Calc) and stay within 1-2 percent for normal loads. Surge loads would probably be ok for 5 percent drop without causing a low voltage shutdown of your inverter.
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