New System, Problems, Solar Daiquiris
Stan-the-Hermit called Friday, needing some bits and pieces to finally get his 24v solar power system running. He’s had his panels for well over a year, having accompanied me on my final run to John’s old Miami Gardens warehouse. They’ve been mounted for months. He left my place happy with an armload of switches, breakers, fuses and solar wire. If I had more friends like Stan I could open a solar hardware store.
I expected to receive a triumphant phone call within 24 hours, but that didn’t happen. He was in a panic when he called Saturday. He’d hooked it all up right, he claimed, but the voltage on the batteries had gone from 17v down to under 13 overnight. What could be wrong? The answer is right there, but let me give you some background.
A while back Stan told me he’d found a Great Deal on some used batteries that came out of a motor coach. “Great Deal” and “used batteries” can, but do not always coincide. Given the voltages he quoted at the time it was clear that they needed a good charging and equalizing and that one might have a dead cell. He did not charge them, resulting in 4 six volt batteries adding up to 17 volts when he connected them in series. I suspected I knew what the problem was and asked if he had read the manual.
“I hooked it up right,” was the answer, but not to what I had asked, so I asked twice more. No, he had not. I braved 4 miles of bone-crushing gullies, terraces and switchbacks to get to his cabin to take a look. He had hooked it up right, as he’d claimed, but it was settled in on 12.8v, which is fine for a 12v system and a real problem for 24v. He could not find the manual, of course. I suspected the charge controller had autodetected the system voltage as a well-charged 12v system and proceeded to run the battery down to 12v overnight.
We hot wired two panels directly to the batteries to get them charging. I left him with instructions to let them get up to a bit over 30v so they could equalize and desulphate and to keep an eye on the water levels. Batteries that dead should have taken a few days, but he was impatient. By Sunday morning the voltage level had come up to 27 volts and he was ready to hook up the charge controller and inverter. That is not what I had prescribed, but it would not hurt anything and might save some damage that could occur if he went away, leaving the batteries unregulated.
I stopped by about 6:00 Sunday afternoon and Stan was a happy camper. I poked at the charge controller and saw that the battery was still taking
50 watts, even as the tall trees up the valley slope were shading his panels. He’d had some of his inner circle over and they’d inaugurated the new 24 volt power system by making daiquiris! It was clear they’d been successful in that endeavor.
He still has 8 more panels and another charge controller to connect before it is done. When he moves his Flexmax 60 over from the 12v system it will be just the ticket for getting those batteries equalized because it can be manually set up for a thorough job, unlike a lot of other controllers that give a mild boost on a daily basis.
By the way, I found the manual online and his charge controller autodetects a 24v battery in a range of 18-30v, so it really did think it was dealing with a 12v battery. Whether you buy your batteries new or used, charge them up before storing and again before putting them into service. Just sitting around discharged is bad for them and confusing to a charge controller. RTFM (read the fine manual).
As for what you use to test your new power system, a blender is as good a start as any.
By: Neal Collier