Off-grid battery bank equalization

Just wondering what others do to equalize their battery banks. I equalize my flood lead acid battery bank on a sunny day. I start the process around midday after the charger has started the float stage. Since the equalization takes 6-8 hours I fire up the generator in the late afternoon and run it into the evening.  It's kind of a pain but I try to do this about every 3 months.

A couple of questions:

1) Does the bank need to be fully charged before starting equalization? Could I start the process in the absorb stage so I could run the generator less or possibly not at all.
2) How often do you equalize your battery bank?

Most of those look like rolls batteries.

Have you read their very useful manual https://rollsbattery.com/wp-content/uploads/2019/11/Rolls-Battery-User-Manual.pdf ?

They have a section on equalization. Mostly to only do it if the specific gravity of the cells deviate more than 0.25-.30 (Ex. 1.265, 1.235,
1.260, 1.210...)

I otherwise haven't equalized in a few years. specific gravity of the cells has always been consistent for me.

If you are charging the batteries according to rolls battery specifications. I am not sure you would need to equalize.

Thanks Jordan,

They are are Rolls except for the one Trojan(I melted a terminal a couple of years ago and that was the only replacement I could find on short notice). I check the specific gravity and top of the water of the batteries about every 3 months as well and usually the readings are pretty close.

Aaron Yarbrough wrote:Thanks Jordan,

They are are Rolls except for the one Trojan(I melted a terminal a couple of years ago and that was the only replacement I could find on short notice). I check the specific gravity and top of the water of the batteries about every 3 months as well and usually the readings are pretty close.

Equalization is sort of going out of fashion since solar arrays are getting bigger and bigger. Equalization was much more common when people had large battery banks and small arrays and most bulk charging was done fast and by generator. That kind of charging leads to differences in specific gravity over time which required an equalization session to balance out. As long as your Specific gravities are close you are good. I do mine once a year now but I dont push the bank much. Usually you should have done an absorb charge before  equalization for full effect. At this time of year I would do a bulk charge early in the day and allow my charge controller to do absorb and equalization. If your array is not big enough you would need to do bulk and absorb with the genny then equaliztion with the solar. You might have trouble pulling it off since the rolls and the trojans have different equalization voltages.

My last bank of lead-acid batteries were "too big" - the capacity of the bank was nominally 20kWh, though the solar array was only about 3kW. And the batteries were all 6V Trojans. I had them wired up series-parallel to try and keep the loading even and I checked the water levels every other month and the specific gravities three times per year. The charge controller and inverter were Outback and the controller had an equalize setting which I used; automatically it would equalize at 30 volts (24V nominal bank voltage) for an hour every month. We had no grid connection nor generator.

I was able to get about five years life on average for those batteries. They say one should replace the whole bank when one goes bad, but that has always seemed a bit preposterous to me (16 batteries at $130 = $2100!!), so I replaced individuals when they showed a bad cell (one chronically low specific gravity).

oh yeah, another thing you can do for a bad lead-acid battery is "bump" it. A bad cell is often caused by sloughing of plate material to make a bridge between positive and negative plates, or formation of a "wire" of lead that shorts the plate. So if you could somehow knock loose that short, then maybe the battery would be OK again! If there is a whole big bank of other batteries around, you can connect some jumper cables strategically to make a nominal 12V connection to that miscreant 6V battery for a few seconds. This causes immediate and vigorous boiling action and hot cables. However, in my limited experience it cured about 25% of the batteries that I would otherwise have replaced; they again accepted charge and specific gravities in all cells matched again after charging. Your mileage may vary.

The vigorous boiling is production of a mixture of hydrogen and oxygen. The cables disconnecting after a few seconds may produce sparks. Exercise due wisdom!