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Wire size is different per site, why

Stewfish

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Oct 20, 2020
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The southwire voltage drop calculator is different from the Alte store chart

For a 6000w inverter that is 48v = 125 amps.

Southwire says 2/0 awg for 4 ft at 125 amps -
https://www.southwire.com/calculator-vdrop

Also says 2/0 https://baymarinesupply.com/bosns_corner_wire_sized

Alte says 4/0 for a lower wattage of 5500
https://www.altestore.com/howto/recommended-inverter-cables-sizing-and-breakers-or-fuses-a62/

Why the difference?

If you scroll down to the "input parameters" section on the southwire link it tells you a recommended wire size and the voltage drop

Also, I'm assuming use the same wire from the controller to the batteries since the voltage will be "48" volts and not my panel voltage
 
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You're comparing two different resources that do two different things.

The Alte table is their recommendation based on their set of assumptions specifically for inverter cable selection. Note that they don't reference length beyond indicating up to 10' in length. Note also that for a 5500W inverter, they're indicating 185A instead of the 125A you calculated.

The Southwire calculator is to simply calculate a voltage drop for a given voltage, current and distance scenario. You can alter it simply by changing the % voltage drop allowance.
 
You're comparing two different resources that do two different things.

The Alte table is their recommendation based on their set of assumptions specifically for inverter cable selection. Note that they don't reference length beyond indicating up to 10' in length. Note also that for a 5500W inverter, they're indicating 185A instead of the 125A you calculated.

The Southwire calculator is to simply calculate a voltage drop for a given voltage, current and distance scenario. You can alter it simply by changing the % voltage drop allowance.
If you scroll down to the "input parameters" section on the southwire link it tells you a recommended wire size and the voltage drop. southwire said 2/0 not 4/0
 
Maybe southwire is thick strands vs using a fine strand welding wire that is tinned and has more resistance

 
For a short cable the voltage drop probably won't be the most significant factor.

The heat generated and what temperature the wire has to be to dissipate it becomes more significant.

I saw an American table showing the max currents for different size wires at different acceptable temperatures.

The shop I use in UK seemed to quotes maximum currents based on the highest temperatures.

Hope that helps
 
For a short cable the voltage drop probably won't be the most significant factor.

The heat generated and what temperature the wire has to be to dissipate it becomes more significant.

I saw an American table showing the max currents for different size wires at different acceptable temperatures.

The shop I use in UK seemed to quotes maximum currents based on the highest temperatures.

Hope that helps
Yes that makes sense. thanks
 
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