Solar wasted watts/volts

starcraft69 wrote:
Ok forget the hot water part If i put a over size system in how does the system dissipate the extra power being generated?

I noticed you edited out your question about using the excess for hot water, but you shouldn't have. It can be done.

But first of all, the water heater has to be on the inverter circuit, and I believe that most RVs aren't wired that way. But we changed ours to the inverter circuit just so we could use it on solar.

(But I'll note that our inverter circuit is 30 amps, and when on shore power, it's very easy to go over that if you're using the microwave, water heater, and a hair dryer at the same time. That's probably why the water heater is usually not on the inverter circuit--that, plus most people would never run their water heater off their batteries, so it never needs to run through the inverter. So it's not hassle-free for us to have the water heater on the inverter circuit.)

When batteries are in FLOAT mode, they need very little electricity to keep them floating. We divert that excess solar production via the use of a solid state relay that turns the water heater on and off depending on the battery voltage. When the battery voltage is high enough, the water heater comes on. As soon as the water heater pulls down the battery voltage, it turns off. Over and over and over, dozens and maybe hundreds of times a second, without drawing anything from the batteries.

You can, of course, just turn on your water heater (if it runs through the inverter), but if it draws more than the sun is giving, the water heater will draw down your batteries. Plus you could forget that it's on. Our method automatically "turns off" when there's not enough sun to operate the water heater and keep the batteries fully charged.

However, we have 1,050 Watts of solar, compared to the 300-400 Watts you're looking at. On the one hand, using the "excess" solar is very satisfying, but on the other, having the water heater on the inverter circuit does require some thoughtfulness when using plug-in appliances that use a lot of electricity.

We'll often reach FLOAT state pretty early in the day, depending on where we are, and will have several hours of hot water generation, so it's worth it to us. If it were going to be much less than that, I'm not sure it would be worth the hassle--to me.

But it can be done.