Jump to content
Genetry Solar Forums

Equalizing Lead Acid Cells

Recommended Posts

I have a bank of "hybrid" flooded lead-acid (12V)batteries. Each cell has both lead-calcium (neg) and lead-antimony (pos) plates.  They are about 9 months old.  I have been charging them up to 14.6/ea at least once a month, and they have never been discharged below 50%.  

After re-arranging the battery bank, I was checking the SG (specific gravity) of each cell, and noticed a couple that were low enough to warrant an equalization charge. So, I charged them up to 15.5V and kept an eye on the bubbles, heat, SG, etc.  I have a couple cells that just wont budge from about 1.21 SG, and they won't really gas beyond a random bubble here and there.  Should I crank up the voltage until they start to gas?  I don't want to over-do it. The other cells all read 1.28-ish and the bank as a whole seems to perform as expected.

Looking into the watering holes, the plates in the lower SG cells are much darker looking vs. the almost-shiny plates in the higher SG cells.

I guess my question is, how high of a voltage is it safe to take these to?  Do you think this is a lost cause?  I am interested in any references you may have for my further reading as well.


Link to comment
Share on other sites

Honestly, I really don't know.  The extent of my experience with lead-acid batteries kinda just gave me a benchmark for appreciating LiFePo4 batteries that much more.  Had a set of SLAs for about 3 years...bought them as 120Ah batteries, and ended up with 30Ah usable capacity by the time I finally ditched the last few.  Conversely, I've had a LiFePo4 battery bank (made with NOS cells for roughly $120/kwh)...been 4 years on it, and absolutely no issues whatsoever.

From what I hear, some battery desulfating equipment can work wonders on lead-acid batteries.

Link to comment
Share on other sites

" appreciating LiFePo4 batteries that much more"

I hear ya, that was my original plan.  I couldn't pass these up for the price though. They were about $60/KWh so I wasn't too uncomfortable rolling the dice.  So far, I don't really have any complaints, the bank still feels fresh, but they are young.  I know they won't last long if I don't take care of them though...

"Crank the voltage up until the max charging current is reached. Probably around C/10. "

These are 200AH batteries, so 20A? I think I would have to REALLY crank it up (like more than double) to get one to pull that kind of amperage when they're fully charged.  Right now, by the time the batteries have charged up to 15.5V they are pulling about 1.25a.  

My thought is to isolate the batteries that have low cells and let them creep up to whatever voltage it takes to start gassing in those low cells. As long as I keep the current under control it should be fine to go as high as 16 or 17 volts.  Anyone see a problem with this approach?  Are there any hard limits I should know about?  Will it open a worm-hole into another dimension if I go past a certain voltage? J/K 🙃

Link to comment
Share on other sites

I'm no certainly battery expert but higher voltages do increase the rate of plate corrosion (erosion), as does high acid concentration but if your cells are already crook blasting them for a bit isn't much of a price to pay if they come back to a good state.

Acid concentration goes up in areas of the cell due to acid stratification if you don't do a charge cycle that gets the cells bubbling to stir up the electrolyte and re-distribute the acid and that usually means doing an equalisation charge once a month.  This only applies to open flooded cell batteries where you can replace lost water.  Don't periodically equalise an AGM unless the manufacturer explicitly says to do it and definitely do not equalise a gel.

Disregard any / all of this with more up to date advice but this is how I used to treat standard open flooded cells many years ago and always got good life from them.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...