Science/Engineering/Technical forums

Hello Everyone,

I'm an Electronics Engineer by training, now working in the battery industry (primarily lead-acid, but also some li-ion), but I also dabble in firmware and power electronics from time to time, as well as a whole lot of Python scripting. I saw the video, as I'm sure many others have, and was interested in both sharing my experience as well as learning from those who are willing to share.

Logan

Welcome
Logan
plenty to read and digest
having a logon makes seeing new stuff much easier
enjoy

I could tap you right now to ask your thoughts on the ideal full-charge specific gravity of the big lead-acids I use in my house power system, made by Rolls-Surrette.
I know I want less than the 1.280 used in car batteries and have a hint why.
Old navy submarine info says 1.250.
One guy I got some batteries from took it much further - more like 1.225, and they never got happy and up to "normal" voltages.
He seemed to think that if less is more, even less is more-er. I wound up adding some 1.280 to bring them up a little and they got happy.

I have a moderately sophisticated 3 stage charging system, with temperature compensation.

Doug,

In my experience, I would never let a cell sit for any extended period of time at 1.225, as that is right about the limit where the plates of the battery start to sulfate, which will kill the capacity of your battery. It's really dependent on how 'deep' you are cycling the batteries regularly. That is, if you're using 80% of the available capacity regularly, keeping the SG a little lower will stretch the life of the battery. I usually shoot for around a 1.265, which tends to be the sweet spot. Generally, you compensate for temperature by adding .001 for every 3 Degrees above 25C and vice versa.

Specific Gravity is kind of a tricky thing. The general rule is that Deep Cycle Batteries should be kept a bit higher than Float batteries, but there are tradeoffs.
High SG gives you good impulse-current response and better capacity, but is more corrosive, so your battery will degrade quicker if it's too high.
Low SG is just the opposite, you take a hit on impulse-response, but get more cycle life from the battery, and if it's too low, you will start to build sulfation on your plates .
Deep-cycle batteries are made with very thick plates that can handle being cycled to very low State-of-Charge (though I would try not to go lower than 20% SoC, as that will kill any battery quick). The float type have much thinner plates, to maximize surface area and have better ability to handle any large transient current draw.

Hope that helps. If you've got any questions let me know.

Your info sounds right given that the factory fill was right in the first place. Here, they did it local and just didn't put in strong enough acid with a full charge dry battery, you couldn't get it past what they put in - you could boil them good till the SG went up of course because now there's no liquid left. That's no good! Dry plates bad!

Yeah letting them sit discharged is really bad, and cycling them is bad too. I seem to be doing OK there, these are pretty old. I have around 1500 Ah in the pack and use around 150 Ah a night so I'm not beating too hard on them now. But the main pack just wouldn't act right till I added a little more acid (which of course they say to never do - and that would be right if they did it properly to begin with) while it was at max charge that it would take - but still not at normal voltage though making a lot of gas on charge.

I found an interesting trick too. Those cheap-o trolling batteries, about the size of big car batteries, are as you say, lots of area but thin plates. They don't live long in cycling service, maybe 2 years. But they take all the surges and are easy to lift to replace too. I use them as bypass capacitors on the big stuff, which is 12 years old at least and still like new (actually better since I *think* I got the SG in range for state of charge). I'm seeing 25.1 volts before the sun comes up in the AM.

Rolls old charts seem to say if you get X (more or less full cycles), but only cycle them 10%, you get 10X cycles. So far, that seems to be true.

there are some new energy storage batteries just coming on the market Carbon lead with 8000 charge /discharge cycle ability
available in 500AH and 1000AH 2 volt cellsonly

Wow, that snuck up on us...after an article a week at least in the science rags about something Li based or some new magic that never makes it to market.

Sadly, a search only shows these available in the southern hemisphere..or China at this point. Shipping lead over that distance to me is not very practical (I'm using Canadian batteries now - so far so good, but...they won't last forever).