Solar batteries — a steep learning curve

We’ve been having some hiccups with the generator for some time now. It had been set to automatically turn on whenever there is insufficient power from the solar panels stored in the batteries. A couple of times we’ve woken up in the morning with no electricity –- and the generator should’ve started up but didn’t. A call to the original installers and a promise to come (twice) did not materialize. So M solved the problem by manually turning on the generator for at least two hours on cloudy days, or when we’re using high wattage appliances, such as the washing machine, oven, or vacuum cleaner.

However, with winter approaching, the prospect of days of continuous rain (yes, it does happen here occasionally) or cloudy weather made us want to know what exactly was wrong. Our local solar energy technician came within two days, looked at the generator and the batteries, even climbed up on the roof to check the solar panels. His conclusion: everything seems perfectly all right, so he suggested installing four more solar panels for an additional 1200 watts. That, he said, added to the 1665 watts from our 9 panels should be more than sufficient for our energy needs.

I always try to get several quotations, so I contacted an industrial battery firm, and they sent a technician to check everything thoroughly. Generator, check. Solar panels, check. Batteries –- not charging. Why? At the bottom was a thick layer of precipitated lead. As you can see, there’s a band of grey gunk there. Essentially our batteries are moribund. solar-batteries

For some time now, we’ve been considering a hybrid wind and solar energy set-up, since there is usually a strong breeze in the afternoon. As well in the spring there were quite gusty winds, and we assumed that, as in Catalunya, it would be windy in the winter here too. It seemed logical to consider the feasibility of a wind turbine, and so I contacted a wind energy firm based in Alicante.

They sent an electrical engineer. Why were we interested in a wind turbine, he asked. I explained that we wanted to supplement our solar panels on cloudy or rainy days. However, he said, your location between 2 mountain ranges and forests is not ideal, due to turbulence. Why didn’t we have enough power, with 9 solar panels providing 1665 watts? Well, that’s what we also wanted to know. After a meticulous check, including a hydrometer reading of the electrolyte in each battery, he confirmed the finding of the previous technician –- only 2 batteries could hold a charge, just barely at 40% and 50%. The other 10 registered 0%.

He recommended German-made BAE batteries (with a designed longevity of over 20 years), whereas the other technician gave a quotation for Slovenian-made Vesna TAB (the same as our moribund ones, which had only lasted 6 years; they were installed in 2010). Right! I’d been tossed summarily into the deep end. Thank heavens for the internet and off-grid user forums. I eventually got to understand most of the acronyms, including the puzzling ‘OPzS’ battery. If you’re as curious as I am, the explanation that this means ‘flooded lead acid battery’ just does not satisfy, but Ortsfeste Panzerplatte Spezial does (‘stationary tubular plate special’). These are lead acid batteries used for deep cycle applications (such as solar energy), often in 2 volt cells. There is another type of lead acid battery, also with a German acronym, but I think that’s enough esoteric German for today, don’t you? Eventually I settled on 12 units/cells of the BAE batteries, the PVS range 1200. These will deliver 28.8 kilowatts.

bae-battery

And it’s not only the batteries that need to be replaced, but the charge controller as well. A charge controller prevents batteries from being overcharged, apparently one cause of the lead sedimentation that killed our old batteries. Here again there’s another acronym to be learned. MPPT means Maximum Power Point Tracking. In other words, an MPPT charge controller self-adjusts to deliver the most efficient charge rate possible. What difference does this make? Quite a lot, especially on cloudy days, apparently. But don’t ask me just yet, I still have to figure out how exactly.

And then two accessories –- a battery monitor that displays the current state of the batteries and how much of the charge is being consumed, and a colour control monitor, that displays a bit more user-friendly information.

After a week of internet-educating myself about batteries, I managed to negotiate the same price for the German-made batteries with higher specs as was offered for the Slovenian-made ones, with all the accessories. And as well, an additional year of warranty –- three years instead of the manufacturer’s two years. I believe I deserve a good pat on the back today :-).

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