AWG wire selection for high-current UAV builds — your go-to sizes? - Page 1
Forum section: electronics / projects

author: skylogic
author_rank: Newbie
timestamp: April 28, 2025, 09:51:00 am
content: Hey guysI'm reviewing wire specs for a 12S 20A setup on a custom hexacopter.I noticed some builders use 18 AWG even for ESC power, which sounds risky to me.I know AWG affects resistance and heat, but has anyone done full-flight current tracking to see what size really makes sense?Do you size based on max burst current or sustained draw?I found this breakdown helpful, especially the resistance vs current part:https://www.motionew.com/blog/battery/what-does-awg-wire-mean-what-does-awg-stand-for/Curious what AWG you're flying with — 14AWG still king?

author: Fflint
author_rank: Frequent Contributor
timestamp: April 28, 2025, 12:48:56 pm
content: AWG 18?. See a typical 6s 1550mah lipo with an xt60 connector. I'm not sure what AWG it is. But the actual copper is about at least 3mm thick (I'll check what it says on the wires later). So that makes it AWG 10 or maybe even 8.You haven't specified battery size in mah, but if it's anything like what I fly with 5in quads... It must be a lot thicker.On the other hand I have some 65mm minis that I do use AWG 18 wire with. So it all depends on the size. What is 20a referring to? Constant/Average current? Peak? Rated?

author: mikeb1279
author_rank: Contributor
timestamp: April 30, 2025, 03:44:15 am
content: 18 AWG is probably fine for ESC to motor wires if your ESC (assuming 4 in 1 ESC here) supports roughly 50A or less. You should be able to find charts from manufacturers which will tell you the max current for each of the gauges of wire. You want to size on max burst current to allow you to operate at wide open throttle without overheating and burning things.My general approach is to find the maximum current supported by the ESC/power distribution board and run the motor wires for that number. I'm pretty amateur at this though,

author: skylogic
author_rank: Newbie
timestamp: May 12, 2025, 01:04:45 pm
content: Quote from: skylogic on April 28, 2025, 09:51:00 am

author: skylogic
author_rank: Newbie
timestamp: May 13, 2025, 10:35:54 am
content: Thanks for the replies, that helps a lot!Just to explain better—my setup is 12S, and each motor pulls around 20A most of the time, with bursts that could go higher. ESCs are rated for 30A constant, 60A burst. I'm talking about the wires from the power distribution board (PDB) to each ESC—not the motor wires. Some builds I’ve seen use 18 AWG here, but that seems a bit light for this kind of power, even if the runs are short.Do any of you use current logs from flight data to guide your wiring choices? Or do you just base it on theoretical/burst ratings?Also, any thoughts on voltage drop and efficiency loss in longer wire runs on bigger drones like these?Thanks again—really appreciate the input!

author: TheBereavingBee
author_rank: Newbie
timestamp: May 14, 2025, 05:16:12 pm
content: You can calculate the resistance you would expect from different AWG using handy tables like this one from wikipedia:https://en.wikipedia.org/wiki/American_wire_gauge#Tables_of_AWG_wire_sizesYou should try to spec the wire gauge to your highest current pull for the lowest voltage drop. Its better to burn those volts to spin a motor instead of using them to generate heat in your wire.

author: DBecker
author_rank: Frequent Contributor
timestamp: May 14, 2025, 06:06:45 pm
content: You aren't finding easy-to-use charts or guidelines because the ampacity of a wire is heavily influenced by its environment.A typical aircraft is going to have vigorous air cooling, which will allow thin wires to carry hundred of amps without melting or severely degrading the insulation. The silicone insulation common in model aircraft will typically be rated for 250C or even 300C for short-time use.You might want to do the calculation of how much power is wasted as heat during a flight, and compare that the incremental weight of additional battery capacity. You'll find that it pushes toward lighter, less efficient wire sizing.

author: TheBereavingBee
author_rank: Newbie
timestamp: May 14, 2025, 10:04:32 pm
content: This is a very good point. Most wires will have a current rating that is limited from the insulating jacket instead of the copper itself. The melting point of the jacket is the limiting factor.

author: skylogic
author_rank: Newbie
timestamp: May 25, 2025, 11:08:42 am
content: Thanks, that helps a lot.I looked at the wire resistance charts too, and yeah—it adds up fast when you're pulling 20–30A, even with short wires. I think I’ll go with 14 AWG just to be safe.Do you ever use current sensors during flight to check voltage drop? Or just stick with the math?Really appreciate the advice!

author: skylogic
author_rank: Newbie
timestamp: May 25, 2025, 11:11:12 am
content: Good point—I hadn’t thought about comparing power loss to battery weight like that.Airflow during flight probably helps a lot with cooling too. I still worry a bit about voltage drop during high current, but I’ll try doing the math and see.Thanks! That was really helpful.

author: skylogic
author_rank: Newbie
timestamp: May 25, 2025, 11:12:51 am
content: Oh, I didn’t think about the insulation being the limit. That’s good to know—thanks for the tip!

author: sleemanj
author_rank: Super Contributor
timestamp: May 25, 2025, 11:55:41 am
content: Forsiliconewire, 25 times the cross sectional area in mm2is a reasonable"rule of thumb"for a maximum current.If you are pulling 20A, divide by 25 to get 0.8mm2which is about 18 AWG.Over say a 30cm run you'll be getting about 2.5W dissipated at 20A, your motors are probably not pulling 20A continuously though, it's a maximum. And as other say in a drone you have better cooling anyway.No harm in being conservative and going with 14 AWG though except for the weight penalty.