use charge controller to equalize?

[kitandk]

Have simple off-grid backup system. Have 12v bat bank (two standard FLA 6v golf cart). low-end PWM charge controller.
Would like to try equalizing for first time.
Have read that this can be done with charge controllers.
As a part of it's automatic operation my CC has an "EQU" (manual calls it "equilibrium", in the manual not "equalization") mode that is supposed to kick in "when the battery recovers from over-dscharge to normal state," This EQU mode is at 14.4v. However, I haven't really seen any voltage quite this high occurring, even though the batteries having been over-discharged at least a few times. Maybe I missed that stage.
Anyway, under "Controller Settings" the manual also lists "overvoltage setting" which has a range from 14.4v to 16.8v.
I'm assuming that this overvoltage is the key to equalization.

Does the following sound like an OK equalization plan?:
1. wait for a nice sunny day.
2. turn off inverter
3. top up water in any low cells
4. leave cell caps ajar for gases to escape better
5. set overvoltage on CC to say 15.6v (just basing this on recommendations for similar batteries from Interstate)
6. let the batteries cook for say three hours (really have no idea how long is good).
7. top up water again if needed.

Please let me know if I'm on the right track here.

[Mike90250]

The first watering, just to cover the cell plates and a teensy bit more. When you EQ, the cells heat up and the water expands, you don't want to dribble acid all over the place. Leave the caps ON. They will vent a lot of gas, and will keep acid splatter to a minimum.
Then you have to give the cells a full BULK and ABSORB charge, and then start the EQ charge, otherwise, it won't actually EQ, but just finish the Absorb stage.
After you start EQ, pause every 30 minutes and check SG with a Hydrometer to see if the low cells are charging up. When all cells plateau, Then the EQ is complete.
It might take you 2 days, one complete day to absorb, one to EQ.
Or you can start the generator and bulk them up in the morning, so the solar can finish it off.at noon -3pm

Lots of variation, read the battery manual, know how to use your hydrometer, and keep acid out of your eyes

[kitandk]

Thanks for advice Mike. So it seems like I might just let the bats do a normal charge (no load of any kind) for a day to make sure they're as juiced up as possible, then set the CC for the overvoltage on the next day and check once in a while till done. I'm assuming just disconnect battery when checking with hydrometer.

One question: once you get used to battery behavior in this regard, do you ever just skip the hydrometer readings and just do equalization on a regular-ish schedule, for example "a few hours every six months" or "a few hours when performance seems to drop"?

[Mike90250]

You find out which is the "lazy" cell, and use that to do 70% of your monitoring, Generally, 1 month EQ cycles, but if you see no divergence in cells, try 2 or 3 months. But the reason is to keep "weakest" cell charged up.

2nd function is to insure the electrolyte is stirred up by all the bubbles to keep it from becoming stratified.

[Sunking]

You are between a Rock and Hard place if you do not have a commercial charger and/or Generator to run a charger. Solar is a very poor source of power for batteries. To properly charge a battery you need a solid source of energy without limits and fully available for 24 hours. Without that, your chances of fully charging your batteries is almost impossible. Let alone EQ them. This is why Off-Grid folks must have a generator to keep the batteries topped off once or twice a week and a monthly EQ charge when needed. It can take 24 hours to EQ the batteries and 6 to 12 for normal daily charging. Solar is NOT capable of doing that.

[inetdog]

You are between a Rock and Hard place if you do not have a commercial charger and/or Generator to run a charger. Solar is a very poor source of power for batteries. To properly charge a battery you need a solid source of energy without limits and fully available for 24 hours. Without that, your chances of fully charging your batteries is almost impossible. Let alone EQ them. This is why Off-Grid folks must have a generator to keep the batteries topped off once or twice a week and a monthly EQ charge when needed. It can take 24 hours to EQ the batteries and 6 to 12 for normal daily charging. Solar is NOT capable of doing that.

And it is generally agreed that when you need to supplement with a generator, either for normal charge or for EQ, the most energy efficient and cost effective way to do it is to put all of the "extra" charging needed on the battery bank using the generator early in the morning before the PV is contributing very much yet.
Then let the PV "run" for 6-8 hours providing not full power, but enough current to keep the battery voltage at the target voltage. Do this if possible instead of running the generator at much less than full load for that same 6-8 hours.

But PV simply is not going to provide enough power for a long enough time to do EQ unless you have already put a near full charge on the bank before the PV takes over.

[Sunking]

So allow me to ask a probing question I already know the answer to. It will wake up the jury.

What specific gravity are you measuring with your temperature correct hydrometer you spent $10 on? Does it say your cells need equalized, or just low?

[B-17]

It is also good to add water or start an EQ cycle only when the battery bank is already mostly charged. (not dead)

B-17, you are being watched, Pointless, redundant comments are not helping your case. Mod

[inetdog]

So allow me to ask a probing question I already know the answer to. It will wake up the jury.

What specific gravity are you measuring with your temperature correct hydrometer you spent $10 on? Does it say your cells need equalized, or just low?

Bingo!!

A lot of people who are new to Lead Acid batteries do not understand the distinction between a bank that needs an extended Absorb to get back to full charge and one that needs Equalization in the formal technical sense (i.e where there is a mismatch in SOC among cells in the series string.)

Is that covered in one of the stickies?

[Sunking]

B-17, you are being watched, Pointless, redundant comments are not helping your case. Mod

All of his comments are pointless, that is what POS SPAMMERS do. Nuke the SOB and be done with it.

[kitandk]

Thanks for helpful additions, inetdog. The diff between lowest and highest cells is .015, and from what I've read, that is the threshold for equalization. However, they are generally all fairly low even when charge controller is reading full charge. Range is 1210 to 1225 among 6 cells. Would appreciate advice based on these numbers, as well as recommendations for a basic 12v charger that is able to equalize or do extended absorb phase on mains power. Mine is a backup system, so mains is available.

[inetdog]

Thanks for helpful additions, inetdog. The diff between lowest and highest cells is .015, and from what I've read, that is the threshold for equalization. However, they are generally all fairly low even when charge controller is reading full charge. Range is 1210 to 1225 among 6 cells. Would appreciate advice based on these numbers, as well as recommendations for a basic 12v charger that is able to equalize or do extended absorb phase on mains power. Mine is a backup system, so mains is available.

First find out what the recommended Equalize voltage or commisioning charge voltage is for your batteries, as well as the fully charged SOC.
Then apply that for a few hours (keeping an eye on battery temp and gassing) then measure the SG on a couple to test cells .
Repeat this process until the SG stops increasing. At this point measure SG of all cells.
If the SG stops increasing but stays below the nominal SG stated by the manufacturer, either you have damaged (probably sulphated) batteries or the voltage you are using is in fact too low.
If the SG reaches the expected value, chances are that your batteries are OK.
Note the voltage and time it took to get to that point.

If your normal charging process results in a steady decline of the SG over the course of a few days, you need to set a higher Bulk and Absorb voltage on your CC.

The details of all of this are, I believe, described very authoritatively in some of Sunking's sticky threads.

[kitandk]

Great info, inetdog. I've noted everything.
One last related question: I've searched a couple times at online retailers for battery chargers that can do equalizing, but I'm not having any success finding them. Must not be using the right keywords. Are there any basic models/brands or search terms you might recommend? I have a very small battery bank (2 golf cart).