Wednesday, June 1, 2016
Off-Grid 12 to 24 volt
My buddy and I just changed his off-grid system from 12 to 24 volts. For months he just sat on $3000 worth of solar electric equipment, waiting for me to be available to help with the installation. He didn't trust anyone else . . . well, anyone else who would work for barter instead of real money.
His old system consisted of solar panels wired for a nominal 12 volts to charge a battery bank of 12, 6 volt batteries wired at 12 volts. A cheap 12 volt DC to 120 volt AC inverter provided house current.
The cheap inverter caused buzzing and humming in some of their electrical equipment plus could barely power the water pump. They'd often fire up a generator to pump water.
The new system has all the bells and whistles. The big upgrade is a large sine wave inverter that has no difficulty quietly powering all their electrical needs.
The first thing we did was to rearrange the 12, 6 volt batteries into 3 groups of 4 batteries wired to provide 24 volts. Those three groups were then wired in series to increase amperage. The solar panels were also wired in series to boost their voltage. He lucked out in that his charge controller was designed to automatically adjust from 12 to 24 volts.
The sine wave inverter was a bit more of a challenge since I was unfamiliar with that particular make and model. However, I knew it needed to have a DC input and an AC output. It could also work as a battery charger so there had to be another AC input from the generator. That was the important stuff. To confuse the issue there were a lot of extra wires to send data to all the special electronic montoring and adjusting gizmos.
Good thing I brought my reading glasses along as it took some digging around circuits and manuals. There was a brief moment of tension until my buddy noticed one of the circuit breakers wasn't completely flipped into the correct position. At the end of the day we flipped a few switches and turned the lights on, so it was all good.
According to the solar electric supplier the 24 volt DC based inverters are supposed to handle loads like water pumps better than their 12 volt counterparts. Kinda makes sense, but it also helps that the new inverter is a quantum leap in quality.
All in all it was an interesting day.