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Monday, July 27, 2015

House batteries



My solar electric system charges a battery bank rather than feed into the grid. While I've got the expense of batteries, I also have power when the grid goes down. For me, that was the whole point.

The batteries are pretty old school: flooded lead acid batteries, the same kind used in golf carts. Every once in a while I have to top off the batteries with distilled water. While doing that the other day I noticed my batteries are now over 10 years old. That's pretty much near the end of their useful life. Since I took really good care of them, they have a few more years in them yet.

Batteries have always been the weak link in off-grid systems. My house batteries are essentially the same technology as batteries from 100 years ago. The best thing that can be said about them is they are good enough. They certainly could be better. Battery technology is making some huge advances, thanks in part to the development of electric cars. With any luck, when my batteries are replaced, the new battery systems will be available for a reasonable price.

Then again, if the new batteries start to displace the old technology, I might go with lead acid again. Why would I do that? If people start to unload their lead acid batteries for fire sale prices, I'd find it hard to say no. After all, they are "good enough."

-Sixbears

12 comments:

  1. Hermit's Baby SisJuly 27, 2015 at 9:24 AM

    We recently replaced 6 golf cart batteries, Sixbears, and I was astounded at the price! But, we got the good ones this time. The last ones were the semi-good, and did not last 5 years. Hopefully these are the final, at least as long as we will need them ...

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    1. Quality only hurts once. I've been getting my batteries from a local Interstate dealer. Proper care can stretch their life a bit.

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  2. When I built my solar system in '99, I bought 8 purpose built deep cycle batteries. I faithfully "equalized" them once a week, checked the water levels once a week, and babied them in every way I could. They worked fine for almost exactly three years, then started losing the charge. They were heavy as hell, I could barely lift one, and they were expensive. I just let the inverter and solar cells go off line, and kept the generator.

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    1. With my first batch of batteries I made every mistake in the book -and still got a solid seven years out of them.

      You did not have a very good experience with your system. Too bad as it "should" have done much better than that. Battery quality varies a lot. Another thing to be careful of is get batteries produced in the same batch. A battery bank is only as good as its weakest battery.

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    2. I just relied on the contractors from Spartanburg, S.C.

      After he installed everything,I found out I was his first customer and he was using me as a training evolution.

      As it turned out, due to our being on the mountain, on a steep slope, with the trees all around us and even higher mountains all around us, solar just wouldn't cut the mustard. The rack of solar cells didn't get enough sun shine in winter. Not everything I have tried to do here has worked, I've just had to accept some failures as the price of being here.

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    3. Maybe I'm lucky that there were no contractors around here and I had to figure it all out myself. My panels sit on the northernmost tip of my land on top of a tall pole. That was the only way to get enough sun. It's also directed a bit more to the west to take advantage of getting more late afternoon sun. Between the early morning fog and mountain to my east, that was the thing to do.

      If you want to talk about failure I should post about my attempt at a veggie burning furnace. Almost burned the house down, and that's agains my lovely wife's rules.

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  3. That's why it's called by that name! lol

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  4. Our off grid experiment was intiated with the 2 volt deepcycle battreries strung to give 24 volts into the inverter. They were used but well cared for by the Canadian Governmernt who had them in one of their nuclear bunkers they de-commisioned.
    They worked well for the 6 years we lived near the 60th parallel but they were a constant battle to keep warm through the winter.
    Our current battery system is a nickle and dime effort using re-cycled 8D batteries which are cheap and despite what is said, they do work quite well.
    The CAT brand batteries are by far the best, just compare the weight with a lesser brand.
    The other end of the equation is learning to use less power!

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    1. Battery weight is a good rule of thumb for lead acid -the heavier the better.

      Conservation is often overlooked but gives the best bang for the buck.

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  5. Lead-acid batteries have advantages over the latest and greatest lithium cells. They don't require 'intelligent charging', a float voltage around 2.4v does just fine. If you get a good set and don't drain them too much or too often, they will last a decade or more. They're also relatively cheap, have a wide functional temperature range and are low maintenance.
    The lead-acid battery's disadvantages are lower efficiency, fewer full cycles before failure and weight. The last one doesn't matter much in a building, good design can minimize the other two.

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    Replies
    1. I keep hoping for a better replacement and have yet to see one for the right price. Maybe in a few years. Lead acid is dead simple, and I like that.

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