Wire Gauge Required Question

BFL13 wrote:
ISTR with MPPT you want a tighter control on voltage drop.

Anyway I am lost here. My question is, "What wire gauge of stranded copper would you need for 16 amps with a 24v system 30ft away (60 ft round trip) with an MPPT controller?"

EDIT--also, please with a 24v panel and MPPT, do you use the 12v figures for the controller battery, but the 24v figures for the controller array wires?

1) Tighter control - yes and no. For array-controller wires, MPPT is all about watts. As long as the voltage on the battery end (which requires different wire gauge and separate calculation) is over 14.4, it doesn't matter, in principle, how much % V you lose. You are losing % of daily watt-hours or amp-hours. If you can afford losing 7% - fine.

2) There can't be accurate answer to the question "What gauge". You need to know what % you are comfortable with, and Vmp.

3) For controller-battery cable you use not 12V but ~14V. For controller-array wire you use Vmp (I think). Usually it's more than 24.

Here is calculator that I, and many others here, use: Southwire.
Choose Overhead or Conduit option, depending on what you are closer to. Yes, 2 single wires 30ft each means 60ft total. I cross-checked the numbers against the "tables" from MPPT manual - normally I don't like tables as they are incremental, so I had to approximate within those increments - and results were very close, like 2.30% VS 2.27%. Sometimes it malfunctions, ex. shows gauge KCMIL 6 where it obviously should read AWG 6.