What is the optimal SOC range for cycling lead acid batteries?

Re: What is the optimal SOC range for cycling lead acid batteries?

ChrisOlson wrote: »

I don't agree with that assessment.

We decided 3 1/2 years ago that we're not going to live in a dark cave here, and we're not going to schedule every load because we got the power to run it when the sun is shining or the wind is blowing. We wanted the convenience and comfort that anybody that lives on utility power has. So I set out to make it affordable so our off-grid electricity doesn't cost us 75 cents/kWh. I got over 7 years of hand-logged data to go by, and now I got a much better fully automatic and more detailed logging system.

If I would've gone by what everybody says is the "only way to do it", instead of gathering proof over the years that judicious and informed use of standby or prime generator power is much more economical and practical over the long term than batteries, we'd still be living in a dark cave and scheduling every load. And today we do it on less fuel in the generators than the average large off-grid system does using the "traditional way" and still scheduling every load and watching every watt.

That's way bigger than 10%. But even if it was 1% the absolute joy of not having to majorly adjust your lifestyle just because you live off-grid is worth every bit of that 1% - especially to my wife.
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Chris

I never said you'd have to live in a dark cave to do it.
Merely pointing out that a lot of people chase after tiny percentages and tenths of Volts when in reality the day-to-day demands on a system do not make such small details worthwhile.

People are always trying to minimize systems: getting "precise" Watt hour number, "exact" battery bank capacity, and "perfect" array size. They end up with a system running on the edge which sooner or later doesn't run at all.

And then I have another headache to deal with.

Re: What is the optimal SOC range for cycling lead acid batteries?

Cariboocoot wrote: »

People are always trying to minimize systems: getting "precise" Watt hour number, "exact" battery bank capacity, and "perfect" array size. They end up with a system running on the edge which sooner or later doesn't run at all.

Oh, I've seen that happen. We got off-grid neighbors that got systems put in by "professional" installers that don't work all that well. They got cheap Trojan L-16's that have gone "flat" in 2 years and only got 75% of their capacity left (if that), they won't run their generator unless hell is freezing over because it's 8-10 kW on a little Outback 3524 and drinks fuel with a big sucking sound, and basically can't even turn on the TV unless they check first to see if their half-dead batteries are above 24 volts. They drool every time they come to our place and go, "how can you even do that????" Well, it's like our water heating system - lots of experience, lots of gathering data over time to figure out how to make it work, and trying many different things to see how it works.

Microscopic data analysis is useful to fine tune something. Big Picture data analysis is useful to design something.

If you start worrying about absorbing your batteries for precisely 3 hours every day, worry that if you don't absorb them precisely based on the sun rising and setting that they're going to stratify, and worry because your daily energy consumption is 8.22 kWh/day instead of your target 8.0 kWh/day, then you're using micro-management techniques instead of looking at the big picture. So while you're worrying about 1/10th of a volt to see if you can turn on the TV, in the big picture you already ruined your batteries because you bought too big of a generator and refuse to run it unless Life As You Know Is About To End if you don't.
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Chris