Bringing life to used batteries

[EvilSpirit1]

Originally Posted by JohnnieB

The electrolyte is roughly 30% sulfuric acid by weight and will have a specific gravity of about 1.277, but the battery acid typically sold in auto parts stores has a SG of 1.265.

Wouldn't a few charge cycles bring the S.G. up the rest of the way? That is, if the batteries were healthy enough to accept a full charge.

[mastrich]

New Batteries would be a quicker solution, some say to empty batteries flush with epson salt and refill, glad i don't want that mess.

[Sergio]

I think the best way if You really want to go through all that trouble is too fill them up with water only, then do a full charge.

That will allow the chemical elements that are already inside the plates to recombine with the water to create the electrolyte.

At that point if the SG is too low You can dump all of the liquid and fill it up with the proper SG solution.

If You just fill them with new electrolyte when they are dead, there is a chance the final SG will be too high and just corrode the plates.

[JohnnieB]

Originally Posted by EvilSpirit1

Wouldn't a few charge cycles bring the S.G. up the rest of the way? That is, if the batteries were healthy enough to accept a full charge.

It might. There are sulfate ions in the form of lead-sulfate in the plates, but they may be so strongly bonded that normal charging won't set them free.

If 1.265 SG acid was used to keep the battery filled instead of distilled water, the SG of the electrolyte would eventually increase to the desired level.

When a lead-acid battery dies a natural death from old age, the cause of death is the sulfate ions in the lead-sulfate are trapped. Adding more sulfate ions in the form of sulfuric acid does help since the battery has ran out of lead, rather than acid.

What I'd do with those batteries is charge them back-to-back (initiate new charge cycles after the charger shuts off) until the at-rest SoC stopped increasing, then adjust the SG of the electrolyte as needed to get the manufacturers recommended SG.




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As Sergio said, you can get the SG too high by adding battery acid instead of water.

[redtide361]

Ok update. I did all the back to back charging after filling with distilled water, I can drive on the batteries full speed any where from 2.5 - 4 miles before it starts acting sluggish. I've charged and let them sit for about 36 hrs pack was at 49.1v and all have about 6.07 - 6.12v on all 8 batteries which is low but possibly salvageable? The short drive time is killing me it's hardly enough to get to the pond or feeder 8>(
I could use some advise about me doing the whole empty completley out & clean with epson salt and add the new acid or...... as of now I have the batteries about half full should I just top them off with the fresh acid?? I pulled up on a incline and sucked every drop of that electrolyte using a turkey baster and all the proper PPE. And all plates are exposed. BTW I'm going to buy new batteries for this cart. But will be trying to revive these from my 36v series cart.

[redtide361]

Oh ya the pack once off charge is like around 54 volts then 36 hrs later was at the 49.1 just fyi guys.

[JohnnieB]

36 hours is about a day too long for getting an at-rest battery voltage reading.
For SoC (State of Charge) estimates, 12 hours rest is used.

The 49.1V average of the eight 6V batteries indicates a SoC slightly over 60% while the individual voltages indicate SoCs from just over 50% up to 60%. (See attached chart.) However, the batteries had rested 36 hours rather than the normal 12 hours, so all of the measured voltages would be slightly higher at 12 hours rest.

Epsom salts and the snake oil treatments, cause the surface of the plates to slough off. This exposes less sulfated lead (negative plate) and lead-dioxide (positive plate), but thins the already thin plates, shortening their future lifespan, and the conductive sloughed off material drops to the bottom of the cells. If this material forms a bridge between two plates on its initial descent, or when the electrolyte is agitated while cart is being driven, of if battery is inverted to empty, a shorted cell is the result and the battery is history.

So the bottom line is there may be some improvement that doesn't last very long, or the battery may instantly become unusable.

[redtide361]

Thanks for the helpful info JB. Ok riddle me this, should I just top off with acid in the half full batteries or should I empty them out completely then turn upside down into a tub then flush and empty again completely then fill with acid? I will be attempting to make time to do so this weekend then start the equalization then once in the cart I'll do the back to back charging and I'll post data and results.

[JohnnieB]

I don't know one way or the other, but the science side of the few functioning brain cells I have left says do half one way and half the other.

[mastrich]

thanks for the info johnnieB, I as hoping someone had light on the epson salt theory, Tve heard a bout it and looked at youtube vids and was very sceptical.