HEEEELP! Your opinion

[ChainsawGrandpa]

I have four PV panels. I think they are 340W @ 34V. Can (and how??) do I use these on a small, portable 24 V system? I am able to do most anything but when it comes to electrical, or electronics it’s like I’m staring at the flight deck of a 747. What do I do, and where do I go from here? Of course I’m kinda in a hurry. I would have done this several years ago but it wasn’t the last minute yet. 😭

[donjuedo]

I have four PV panels. I think they are 340W @ 34V. Can (and how??) do I use these on a small, portable 24 V system? I am able to do most anything but when it comes to electrical, or electronics it’s like I’m staring at the flight deck of a 747. What do I do, and where do I go from here? Of course I’m kinda in a hurry. I would have done this several years ago but it wasn’t the last minute yet. ��

The panels should connect to a charge controller. Cheaper ones are called PWM and are less efficient, but work. For a little more, MPPT are available, and these are more efficient. MPPT is short for maximum power point tracking, which means it intelligently tracks how much the panels can deliver at any point in time (depends on sunshine of the moment). The charge controller (of whichever type) delivers electrical energy to the batteries. MPPT "milks" the panels for all their worth, all the time.

You'll need to decide on how you wire the panels. In series, 34V + 34V + 34V + 34V = 136V. But in very cold weather, the sum can be higher, and the charge controller must be rated for it. In parallel, 4 panels at 34V deliver 34V but with more current than just one panel. If you want to keep things simple and safe for now, this is what I'd recommend. The only downside I see so far is that the charge controller might "turn on" (start charging the batteries) a little later at sunrise and turn off a little sooner at sundown. But at least it works, and you will have time to learn details to get a tad more energy, if you want. Or keep the panels in parallel forever, which is not bad.

How much energy can you expect? Typical planning says a sunny day has 6 "sun hours". Daylight hours are longer, of course, but gradually ramp up to peak in early afternoon and then ramp down gradually. Rather than get into all the math, people simply plan as if the sun shines for 6 hours, and peak brightness.

So 340 Watts x 4 panels is 1360 Watts. 1360 Watts x 6 hours = 8160 Watt-hours (or 8.16 KWH). As a single guy living alone in an apartment without a washer and dryer, and with a gas stove and oven, I averaged 8 KWH in Spring and Fall (no need for heating or cooling). Your situation is likely different from mine, but at least you have a reference for comparison.

But the panel ratings are best case scenario, like full sun, located at the equator, optimum temp, etc. Panel output will be expected to drop to 80% after 20 years or so.