Copper wire gauge and max amps

Do not skimp on your wiring across your solar installation. Pushing too many amps across a wire that is too small can cause fires and short your installation – this is dangerous!

A rightly sized wire reduces resistance and can assist with reducing voltage drop.

For example, in my system i have a 1000W inverter attached to my 24v battery. If i’m pulling 1000W, then amps 1000W / 24V = 41.67A. Meaning i should be using a 6 gauge wire (see below) between my battery and inverter.

Solar panels can be attached in series to increase their voltage, this is one method for reducing amps over the wire. But, keep in mind that if you raise the voltage you will need a way to reduce it back down to match the voltage of your battery. i.e. in most cases it would be best to utilize a MPPT solar controller to automatically convert the power from your solar panels to you battery.

As a GUIDE to maximum amps across a copper wire ;

  • 14-gauge wire: 15 amps
  • 12-gauge wire: 20 amps
  • 10-gauge wire: 30 amps
  • 8-gauge wire: 40 amps
  • 6-gauge wire: 55 amps
  • 4-gauge wire: 70 amps
  • 3-gauge wire: 85 amps
  • 2-gauge wire: 95 amps

Note : length of wire also determines its resistance. I have not covered it here, but if running wires over large distances you will also require a lower (fatter) gauge wire. Try to keep high amp loads across short distances. i.e. keep your inverter near your batteries.

Home Solar Experiment

So I’ve been busy building a new solar array, mostly as a hobby and its been crazy fun. Electrocuted my self twice, but luckily nothing too bad.

I’ll write up some more detail round the build, the metric collection and the things i have learnt over my time.

Keep in mind that NZ is in the southern hemisphere, so its winter as i’m writing this. Low sun hours! Stats publicly available via grafana here – https://grafana.sigtar.com

For now a quick summary of my build below;

Build Details;

  • Solar Controller 1 x EPEver MPPT (Max 30A, 720W @ 24v)
  • Solar Panels 6 x 100W (5.2A 19.25V) – 600W in series & parallel (10.4A x 57.75V)
  • Battery 4 x 6V (US Battery 232AH @ C20) – 24V in series
  • Inverter 1 x EPEver 1000W (Pure sine wave) – 24V DC -> 230V 50Hz AC

Controller Settings;

  • Boost and Equalize duration : 120M
  • Over Volt : 32
  • Equalize Charge Volt : 29.6
  • Boost Charge Volt : 29.2
  • Float Charge Volt : 27.6

Software details;

  • Influx DB – 90 day retention
  • PHP script polling Solar controller every few seconds – parsing results into db
  • and of course Grafana!
  • all docker images on UNRAID server

Whats next?

  • ATS – maximize my solar power with 24hr loads :p
  • Batteries – Switch to LiFePO4 batties (Lead acid suffers from small DOD of approx 50% and voltage drop under under load)
  • Wind – hard to find anything that would work in my urban area. Must retire to the hills before i get into that! ;)