So much misinformation here!

Ampacity and voltage drop are two

**DIFFERENT** issues! Ampacity is the critical one here.

**Ampacity** is defined as the maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.

**Voltage drop** is self-explanatory.

See the ampacity tables at:

Cerrowire.com 12 gauge wire is rated around 20 amps

Yes, but ampacity is for a conductor run, and designed for ac power.

It allows any length conductor, and uses derating for conditions such as number of insulation layers, pathway shielding, number of conductors in a pathway etc.

It is an insurance protection metric.

when calculating short run, or specific runs, ampacity charts don’t really have any use. What matters is voltage drop, and ALLOWED voltage drop.

short runs under a meter in length can be used to calculate at voltage drop and use acceptable loss percentage for the result.

Most consider 10% loss extreme, 5% a weak acceptable figure, 3% ok for most uses, and 1% or less as the ideal.

If you size a cable at specified length in a calculator program, and specify 1% voltage loss... the wire size will be a safe figure to use. And #12 can handle 30 amps at 10%, 25 Amps at 3%, and 20 Amps at 1%.

So, x4 for the capacity, and you have a maximum safe load of 120A... with a voltage loss of less than 2 volts... around 1.2V

Shorter runs equal less loss, and more amps capability, but in no way Will they handle 320A for more than the time it takes the solder on the board to vaporize... likely around 30 seconds...