# Choosing correct wires for power regulators

#### Sasuke Uchiha

Joined Jan 15, 2022
21
Hi.

I have a 20V battery connected to my pcb. I need a 5V/3A output, so I am going to solder a 5V step down module to my circuit.
Since I know a USB C cable can handle 3A, I am going to wire a USB C cable to the output pins of the step down module. At 5V/3A, that will be a total of 15W going through the cable. I am not sure if the same cable type can be used for the input since the voltage from the battery is 20V. Making it 20V*3A = 60W going in to the step down module through the cables.

I have seen AWG charts, and they don't mention anything about voltage or wattage. How do I know if the USB C cable will be safe to use for the input of the step down module?

#### DickCappels

Joined Aug 21, 2008
8,711
That's because the conductors don't care about wattage or voltage. They only care about current because current is what can make them hot.

#### Sasuke Uchiha

Joined Jan 15, 2022
21
So, if the cable can handle 3A, it can do it at 5V/3A, 20V/3A, even 100V/3A?

#### Lester Burnham

Joined Apr 21, 2021
3
While it is true that the only important thing when selecting a conductor is the amperage, the voltage levels to be used must also be taken into account for insulation reasons. In your case, with 20V it is correct to use the minimum insulation, except for the bare conductor case obviously.

#### Sasuke Uchiha

Joined Jan 15, 2022
21
Unless its marked on the cable, how do we know the rating of the insulation?

#### DickCappels

Joined Aug 21, 2008
8,711
So, if the cable can handle 3A, it can do it at 5V/3A, 20V/3A, even 100V/3A?
You understand.

#### DickCappels

Joined Aug 21, 2008
8,711
While it is true that the only important thing when selecting a conductor is the amperage, the voltage levels to be used must also be taken into account for insulation reasons. In your case, with 20V it is correct to use the minimum insulation, except for the bare conductor case obviously.
You might find it in the manufacturer's catalog. I usually go by wire gauge or copper cross-sectional area.

You find these charts by searching for Electrical wire table. Searching for Wire Table seems to bring backyard and lawn furniture : -)

#### crutschow

Joined Mar 14, 2008
29,825
Unless its marked on the cable, how do we know the rating of the insulation?
If you can find no information on the cable (or a similar cable) then you just have to look at the wire insulation thickness and compare it to wire with a known insulation voltage rating.