Why does Victron call for such large wire sizes

[jameshowison]

In the manual for the 48v 3000W Victron Multiplus it specifies 2AWG wire from the batteries/busbar to the inverter. I'm trying to understand why.

https://backwoodssolar.com/product_attachments/Datasheet-MultiPlus-II-48V-3kVA-35-50-120V-EN.pdf

Regular draw is 3000W ie about 62 amps (at 48v, so actually fewer at usual voltages). Peak power is 5500W (ie about 120amps, rounding up).

Using a wire calculator at explorist.life even at 20 feet length (ie 10 feet positive, 10 feet negative), 48v, and 120amps (and 3% voltage drop) I'm seeing 6AWG specified.

The Jakiper 48v server rack battery is saying 120amp max draw (and less than 100 continuous), so that matches well with the inverter. They specify 6AWG (and that's what they use internally within the battery). Even paralleling the batteries, which could increase the draw, the draw is not going to be higher than 120amps (since that's the max the inverter will pull).

So I don't understand why the manual specifies 2AWG rather than something like 6AWG.

Likely I'm missing something, but can anyone help me resolve that? Is it an attempt to minimize voltage drop, resistance, and therefore ripple?

 

[MichaelK]

A combination of both. Both voltage drop and ripple current increase as wire thickness decreases. Personally, I would consider 2AWG too small. The smallest cable I'm using right now from the battery to the inverter is 000.

 

[jameshowison]

A combination of both. Both voltage drop and ripple current increase as wire thickness decreases. Personally, I would consider 2AWG too small. The smallest cable I'm using right now from the battery to the inverter is 000.

For a 48v system or a 24 or 12v system?

 

[MichaelK]

For a 48v system or a 24 or 12v system?

I'm using 000 for my 24V system and 0000 for my 48V system. But, both of these are whole-house, hard-wired inverters.

 

[HRTKD]

The 12 volt Victron inverter/chargers also specify large cables along with large fuses. I'm into overkill, but Victron seems to take it to a whole new level. I'll be using 2/0 cables. Since I have plenty of 2/0 and the run is short (30" one way) I'm going to run two cables for each leg.