Inteligent load control

[Frederico]

Hi there, New to the forum.

I have a cabin with a 48v off grid solar setup. I have 1500w of panels, a 3000w inverter and eight 6v, 220ah golf cart batteries in series.

The cabin is only used intermittently and so most of the time the batteries are at full charge with only a float voltage being generated by the panels.

I would like to make better use of the panels when the batteries are full and the sun is shinning. I'd like to power some air pumps for lake aeration purposes.

Is there something I can include in my system that would allow for intelligent load control?

ie: Run three pumps if sun is at full, run two or one pump if semi-cloudy? I also don't want to pull from my batteries as I'd like them to be full whenever I show up at the cabin.

Note: I have a AMPINVT 60amp charge controller. (cheap unit, I know) It seems to have a load control function but only by timer or by voltage. The challenge with the control by voltage is, the panels can be putting out voltage even in low light conditions without the amperage to back it up. It ends up draining the batteries.

I've search the net for relays or cut off switches but most of what I can find are low voltage cut offs for protecting batteries. I need something that operates in the "battery full" range.

Any guidance is much appreciated.


Fred

[PNPmacnab]

Solar is fertile ground for smart use of power. I have an off grid camp where any excess power goes into heating domestic water. It is a proportional system that looks at array voltage and when it raises over natural power point voltage, it diverts just enough power to drop the voltage back to power point. Looking at panel voltage is a very effective method of diversion. It never touches the charge of the battery by operating only off raw panel voltage. I actually operate several water heaters on a priority basis and have a separate 40 gallon tank just for laundry. The upper part of the tank easily heats and often more than enough for laundry. Tank stratification is very effective in solar giving. My fridge operates only when the sun is shining and uses battery power just for starting. My battery is only at full charge. MY pump looks at battery voltage and only operates when the battery is full. I have next to nothing for a battery for the house. Wife wanted a dishwasher. Wrongly, I thought I had married one. So I got her one and it is quite easy to operate one on a small camp system. The dishwasher heater runs off panel voltage. Clothes washer also runs off a modified inverter and needs no battery.

It is possible to effectively run off solar s it is produced and live better than others who spend three times more for solar. It requires some thought. A small pilot panel used just for determining how much solar power is available would be a good start with voltage relays to switch in additional pumps. Array voltage could also be used. Another voltage relay to insure battery level is sufficient to divert power. Just ask yourself what you would look at to determine when there was excess was available. These systems aren't found on Amazon and the solar world can barely hook up four wires to a controller. It is nice not to be dependent on commercial products.

[Frederico]

Ok, thanks for the reply. Sounds like your system does basically everything I'd like to do and more! Can you point me in the right direction for hardware? What kind of voltage relay are you using? Is the relay installed directly between the panels and the charge controller or between the charge controller and the battery?

Fred

[PNPmacnab]

Sorry, I can't help much. I build all my own equipment and every site has different requirements. If you can think logically there are modules that can be combined to emulate functions. That turns out to be very expensive. It is fun to use a $5 board like the arduino NANO which is extremely powerful for these applications, my fridge runs on one. Here is an example of my water heater diversion control. This is the best PV diversion out there proportionately diverting 5-1500W instantly.

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