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solarnewbee:
Quick question because I’m not familiar with charging sealed lead acid batteries. I’ve been letting the mppt charge controllers internal program do the job. It is user selectable up to a point then you get a fault warning. I have heard on the is forum talk of numbers for wet cell or 60v. Any thoughts?

lighthunter:
For sealed AGM batteries
Bulk: 57.6- 58.4
Float: 54 - 55.2


Somehow thought you had FLA
Here that is....
Lead Antimony Flood lead acid.
Bulk/absorb 58.8V daily
Float 54V. Daily
Equalize 64V never, -Ha, yes its necessary but only while watching whats happening with SG meter etc.

Lead Acid batteries come in several flavors and they are ALL different. So starting there, you said wet cell or FLA, assuming Lead antimony type since most deep cycle like Trojan are this type.

Then there is the "character of the battery" through the life of these batteries their needs can change so you need to watch behavior and adjust accordingly. Some dont like higher voltages and boil water instead which can shorten life. So good care of FLA is not "one size fits all"

If they are new and true "deep cycle" bulk/absorb starting point is 58.8V.
Meaning charge with available amps staying below max battery charge current until voltage rises to 58.8V then maintain that voltage for absorb time until current drops significantly. Then terminate charge.
Record specific gravity, and ending current.

If your batteries are taking a fair amt of current and the voltage never builds to 58.8 then maybe 57.5 is the right number.

Try to hit the sweet spot, dont push them too hard too high voltage nor too soft and monitor capacity and SG. Equalize can bring capacity and SG back up a bit but you also corrode the positive electrodes by the harsh treatment and so loose life that way.  Sometimes you cant win no matter how good you treat em then other times.... true story, the auto charger on a golf cart failed to terminate. Ran all weekend, there was literally no water left in them. I grabbed a new 3Gal jug of drinking water, almost  all the water fitnin the 6 batteries. That was over a year ago and the batteries still act like new, nearly 4yrs old now. I dont expect them to last 10 years but they see the worst abuse imaginable and no signs of weakness yet. By the way those perform i would say daily hard work is better than sitting idle. Seems like deep FLA batteries that get treated soft become weak. I will look at brand name and update.

Everyone has different ideas about how to treat lead acids. Many on this forum know more about it than me so consider the sources and the environment. Cold is higher hot is lower for example.

By tbe way, wheres Doc Hubert? havent heard from him in a while. hope he didnt bolt the hatch down yet ;D. Those politicians gettin on everybody's nerves lately. Least our supreme court shot down their latest scams so we dont hav to wear diapers on our faces at work anymore.

All the best, have fun!

lighthunter:
Heres a good visual of charge voltage profile of the lead acid types i ran across today. The numbers are slightly different from info in previous post but as mentioned, its best to watch behavior of lead acid and adjust setpoints on behavior. A bad connection can also raise havoc with auto chargers and leave your battery uncharged or other malfunctions in charger can overcharge and ruin batterys. This is why with lithium you always need a secondary circuit to verify and monitor to prevent damage. Many a ruined FLA or AGM couldve been saved by using Battery monitor systems as well. It just didnt get popular since lead acid isnt as expensive and usually wont burn up your property ::)

Pete:
Hi LH, I have BAE Valve regulated Lead acid batteries, they say to have the float set at 2.3 to 2.4 volts per cell.
It seems that each type of battery is different slightly.
So on a 12 volt system mine would be 13.8 to 14,4 volts.
I guess that gel batteries aren't open so cannot be charged as high as the others.
My regulators are adjustable, so far they are doing a good job.
I try to never let my batteries go under 80% charge if possible, they have been down to 70% once of twice in winter, but now with more panels they don't get down much at all.
I reckon a 20% discharge is enough, I want them to last as long as possible.
Cheers
Pete

lighthunter:
Hi Pete :), i know nothing about BAE, i looked up a pdf about them and it agrees with your 2.4vpc finishing/absorb voltage 14.4 for 12v or 28.8v daily finish for 24v.  The float they refer too is after charging is done and just to prevent or balance self discharge i think. That voltage appears to be 2.23 vpc or 13.38V, 26.76V.
With daily use solar, float doesnt happen too much. Those really look like nice batteries, they should last a long time.


I have a lithium bank but also still have the 510Ah 48v fork lift battery. I just cant seem to kill it. I was gonna get rid of a month ago because it always acted full but wouldnt supply much before voltage fell. A couple weeks ago i decided to deep discharge it and bump the charge voltage up from 57 to 59, what a difference. Its now back doing useful work. Very wierd because this battery used to resist high charge voltage and boil like a pan of water on high heat. For some reason it seems to act more normal now. Its previous life ended with more than a year in storage at about 1.6vpc.
I know they say FLA last longest with only mild disharge 20% like you say but it seems like this one acts a bit like a horse. If you go out and run once in a while they stay in better shape. In other words an occasional  deep discharge somehow improves performance.

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