# What wire gauge would work best at 3 amps over 1 meter?

Ive got two Xml’s at 3A from a b3flex. they are seperate from the battery and the driver and i want the best gauge wire to make sure i dont loose my current. its over about 1m.

thanks
tom

Use the largest you can afford in terms of physical thickness, physical weight, cost, flexibility…

That said, Anything over 18Ga is plenty…

The resistance of 18Ga is about 21mOhm per meter, so at 3A

3 * .021 * 2 = 0.126V

You’ll be dropping 0.126V in the wire.

Using 16Ga would give you

3 * 0.013 * 2 = .078V (78mV) of drop in the wire.

carries PWM current instead of DC then it’s a little more tricky.

The b3flex is a buck converter. With two xml’s running at 3 amps. As long as your supply voltage is (1.1v + loss in the wire) above the output voltage it should work properly (3 amp output) with adequate rated wire. 22AWG maybe borderline as small as you could possible go without heat issues and more wasted energy than larger wire. But as PilotPTK suggested the bigger your application can except the better, less losses. I would also suggest using high strand count silicone wire for something that needs flexible movement.

Echoing PilotPTK’s recommendation… 18G copper and decent solder (if needed) will be aplenty.

What sort of frequencies of PWM are you thinking of? Skin effect will not change things measurably at the normally encountered rates.

You guys recon 16awg will be enough? Thanks for all the help :bigsmile:

That should pretty well cover it. If it works for you go with it.
What is your battery setup by the way?

Somebody may publish the spectrum of a PWM waveform. Generally the highest freq. contained in a pulse is MHz = 350/(risetime in nS).
I’d go with heavy wire and check with an RMS meter that the drop doesn’t exceed some benchmark, maybe <10% of the battery voltage.

PWM over a 1m length should not be an issue. There may be some additional RF noise broadcast by the wire. The actual light output should not be affected much, if at all.

I modded a hunting light for a friend, that had about a meter of wire between the driver and led. The driver was contained in the battery pack that clipped to your belt. I made a aluminum head to contain the led and reflector with 20AWG wire running to the driver in the battery pack. Looked like one of those big headed bike lights. Actually about the size of a Maglite head since a did make it fit a KD aluminum maglite replacement reflector. I used a 555timer to create a pwm signal with a driver that contained a pwm input running at 3 amps. The 555 timer allowed me to build a circuit with a pot to control the brightness by turning a knob.
There was no problems with pwm signal or resistance in the wire. The driver was a constant current buck driver so it slightly increased the output voltage to maintain 3 amps to the led.