I go through this crap every winter…

Once your solar power system’s charge controller hits Float it’s easy to imagine that means your batteries are fully charged, which is not entirely accurate. For a full charge the batteries still need a long sunny afternoon’s soak in a relatively high-voltage/low amperage charge – which is to say, basically, that they need it to be summer. And sunny*. This is why solar power is probably never going to be a big industry in, say, Finland. Or the PNW. Unless, of course, it’s subsidized by a stupid, massive grift of an “infrastructure” spending b…(I’ve got his mouth! Get the cuffs on quick, he’s biting me!)

(ahem) Ranting Joel having been stuffed back into the closet, my point is that solar power systems need certain environmental conditions to work well, and those conditions don’t always prevail even in the most otherwise amiable locations, such as the SW desert. Which is why, headed toward the winter solstice after two VERY cloudy days, I wake to be greeted by sights like…

Happily, deep cycle batteries are constructed to forgive a level of misuse, which is why nobody with a choice just powers their cabin with a couple of old car batteries, which are not. My relatively new golfcart batteries can withstand considerably lower levels of charge without too much concern over damage – though I tend to be a worrier anyway, which is why I have that readout on a prominent wall in the first place…


*…and oh by the way warm, because the third thing lead/acid batteries need is for it not to be below freezing, where they don’t work so well chemically anyway.

About Joel

You shouldn't ask these questions of a paranoid recluse, you know.
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6 Responses to I go through this crap every winter…

  1. jabrwok says:

    So ideally would that number never change? I don’t know enough about electricity to really follow the issue:-(.

  2. Joel says:

    Ideally you’ll get similar readings under similar conditions, which is how you can tell when things are going wrong. But 5:30am in June doesn’t offer the same conditions as 5:30am in December, so a lower than desirable voltage reading doesn’t mean anything is actually wrong even though it may trigger mental alarm bells in the overly wary, such as myself.

  3. Steve Walton says:

    12.13 volts is mostly discharged, but not into serious damage territory. Worry whether they will ever hold a charge again if you see them get down to 11.4 or so. Most inverters cut off around that level to “prevent battery damage”, but of course it’s already done.

    You probably have a chart of charge percent vs. voltage pasted on your wall, like I do. The problem is, it’s not valid unless the battery has been at rest (disconnected) for at least 15 minutes, and it depends on temperature. Determining how much power you have left is damn near impossible with lead acid batteries.

  4. Terrapod says:

    If you are disposed to become a digger rat, and sink a shaft about 20 feet down, build a concrete bunker with access pipe about 3 ft in diameter with steps (rungs), then fill it all back in with a giant Styrofoam plug at the entry, you could have your batteries down there nice and stable temperature all year round. The added benefit is that with some ventilation pipe and filters it could double as a nuclear bunker and secure temperature controlled hidey hole, of course, to be safe, it would need another exit in an alternate direction.preferably horizontal for a good stretch. All bets are off if you hit ground water.

    Sounds like a good project and I think one of your neighbors still has that backhoe somewhere out there.

  5. Joel says:

    Riiight. I’ll get right on a 20-foot-deep bunker. Good plan. 🙂

  6. Dave says:

    Problem is they aren’t all that much better in places with excess sunlight. We have huge number of panels plus solar battery – this week when we had two day without a single cloud and over14 hours per day of sunlight we never got above 60% of capacity because the temperature was too high (over 40 degrees celsius) for the panels to work efficiently and charge the battery.

To the stake with the heretic!