2022-01-25, 05:50 PM
Wire size is a function of current over distance, so there is no one size fits all answer. However, the size (or gauge) of wire to use is easily calculated if you know your load. How much a device draws in current should be listed in the device specs somewhere. Blue Sea Systems has a handy app for calculating circuit sizes here: http://circuitwizard.bluesea.com. They have a handy app for your phone, too.
Be sure to use a quality tinned wire, as it meets ABYC standards that regular automotive copper wire does not. Not worth "saving the money." I work on a lot of boats and the cheap stuff doesn't hold up well in the marine environment. So while it seems like you're saving money upfront, as the wire breaks down and resistance increases, you introduce voltage drop into the circuit and that throws off your calculations. Voltage drop in a circuit is essentially electricity that spills off a wire as heat with less actual voltage reaching your device. So, while you think your device is getting 12.8 volts because that's what's in the batteries, with a 10% voltage drop, it might only be getting 11.52 volts. That difference can affect performance. Save time and money by doing it right the first time. And always remember the length of a circuit is from the source to the device AND BACK, so your 6m distance is a 12m circuit. Even with a small load, like an ESP32, you might find that will need a decent size wire.
I'd also recommend up-sizing your wire. If a circuit calculates to 18 AWG wire for a circuit with <3% voltage drop, consider using 16 AWG instead (wire gauges are backwards, at least here in the US - 18 is small, 10 is big, 2 is huge). Upsizing wire helps minimize the aforementioned future voltage drop due to age, resistance, etc., with the idea that you'll hopefully never have to replace that circuit. Having rewired many boats, I can tell you that's not a fun job.
Best of luck with it! I just installed my first ESP32 with SenseESP and a capacitive sensor on my holding tank and it has really helped our live-aboard lifestyle! I'll be adding more soon!
Be sure to use a quality tinned wire, as it meets ABYC standards that regular automotive copper wire does not. Not worth "saving the money." I work on a lot of boats and the cheap stuff doesn't hold up well in the marine environment. So while it seems like you're saving money upfront, as the wire breaks down and resistance increases, you introduce voltage drop into the circuit and that throws off your calculations. Voltage drop in a circuit is essentially electricity that spills off a wire as heat with less actual voltage reaching your device. So, while you think your device is getting 12.8 volts because that's what's in the batteries, with a 10% voltage drop, it might only be getting 11.52 volts. That difference can affect performance. Save time and money by doing it right the first time. And always remember the length of a circuit is from the source to the device AND BACK, so your 6m distance is a 12m circuit. Even with a small load, like an ESP32, you might find that will need a decent size wire.
I'd also recommend up-sizing your wire. If a circuit calculates to 18 AWG wire for a circuit with <3% voltage drop, consider using 16 AWG instead (wire gauges are backwards, at least here in the US - 18 is small, 10 is big, 2 is huge). Upsizing wire helps minimize the aforementioned future voltage drop due to age, resistance, etc., with the idea that you'll hopefully never have to replace that circuit. Having rewired many boats, I can tell you that's not a fun job.
Best of luck with it! I just installed my first ESP32 with SenseESP and a capacitive sensor on my holding tank and it has really helped our live-aboard lifestyle! I'll be adding more soon!