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gabriel

cable size 48v system, 4x250ah batteries, 4m

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hi guys

what would be the right cable size between the batteries [250ah] and the inverter for a 48v system where the total cable length in less than 4m :huh:

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Depends on the maximum current draw of the inverter... the one thing you didn't specify :-)

Let's say it is 5kva. That's about 100 amps give or take. You want a voltage drop of less than 3%, preferably around 1%.

35mm^2 has a resistance of 0.65Ω per kilometer. You have 0.004 kilometer. So

0.004 * 0.65 * 100 ~= 0.3V. That's less than 1%.

25mm^2 has a resistance of 0.9Ω per km.

0.004 * 0.9 * 100 ~= 0.4V. That's also less than 1%.

If you look at some wiring ampacity tables (google) you'll see that the 25mm^2 will run quite hot at full load. So 25 in open air is fine if you only run full load for short periods. I'd go with 35.

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