solar question

Almot wrote:

mike-s wrote:
So? It's parallel connected. You match current in series, match voltage in parallel.

So, mismatched voltages in parallel will magically become matched :)

You claimed his panels had mismatched wattages. Now you're changing, and claiming they have mismatched voltages. It seems you don't understand the relationships between voltage, amperage and wattage as it applies to solar panels.

I assume his "rangy" panels are Renogy.

RNG100D 22.5 Voc / 18.9 Vmp
RNG150D 22.5 Voc / 17.9 Vmp

There's a bit of a difference in Vmp, but not enough to make a significant difference. Look at the I-V curves for those panels. The 1V difference in Vmp is so slight it's hard to judge how little difference in power output there is, maybe 1-2%, if that? In fact, on the I-V for the 150, it looks like there's no difference. But, that would only happen if using an MPPT controller, anyway.

With a PWM controller like on his Yeti, the panels would be pulled down into the Isc range anyway, where the very slight mismatch in panels makes no real difference. They're all going to put out very close to Isc, regardless of their rated Vmp.

In parallel, "mismatched voltages" really only becomes significant when you're looking at panels with a mismatched number of cells (e.g. 60 cell vs 72 cell).

He is going to have a problem if he wants to take full advantage by changing to a controller/battery bank, though. He's pretty much maxed out for any reasonable PWM (he'll have 60A), and he'd be losing about 100W by putting all his panels in series and using MPPT. He may need to look at getting two controllers so he can split the panels between them.