sla desulfation

[dnix71]

We have a lot of sulfated sla's at work I could experiment on. If sulfation is actually the formation of hard crystals why not untrasound or deguassing to break up the crystals?

[ghurd]

1st, I am not a big believer in it.

But I have seen it work.  By accident.
I have a feeling it was basically the same as blowing the whiskers in a nicd.
Used a Very lame, Very old, 7AH SLA for testing because the terminal voltage changed quick and easy.
Charging current about 1C.  Dump load current about 2C.  Tight hysteresis and fast acting.
Dump load controller was probably set around 13.5 to 14.0V.
Result for the battery was 1C in or 1C out, but really fast.  (couple/few 100Hz?)
The battery got better.  Not good by any means, just a little better than it was.

I could be way off base about what actually happened in the battery.

Some guys claim an equalization charge works for weak SLAs,
though I never had any predictable luck with that either.
G-

[dnix71]

My boss brought in a 24v skateboard scooter. He said it had been sitting for over a year because one day it simply quit and would not recharge or operate. He had a spare battery set that was unused but also had been sitting around for a year. That pair had 11.75v each and recharged. The first pair is about as stone cold dead as they get. About .8v each.

The problem with the scooter was wires shaking loose from vibration while running. I fixed that. 2 days on a charge brought the dead batteries up to about 4v each and no amps. Even on the "80-amp" car start mode charging there is no current flow through the dead batteries, but they are not swelled or banged up or cracked.

If 'pinging' or 'ringing' with a common desulfator works sometimes, why not mechanical shock? Certain frequencies of sound around 30k Hz and up are supposed to make flashes of light in water because it resonantes at that frequency. Is there a mechanical resonant frequency for hard PbSO4 that is within the range of a speaker horn?

I was wondering if anyone had tried using an ultrasonic cleaner or maybe even a strong magnetic hysteresis loop like the one's used to bulk erase tapes or degauss a crt.

A paint shaker would probably just destroy the battery internally. I was thinking of something a little more subtle.

[ghurd]

My solder guy uses ultrasonic cleaners for rebuilding/repairing clocks.
(electrickery got nuttin' on making clock parts from scratch!)
He uses the small and large HF versions, a medium-large version from a decent company, and a very large one he made from 4 or 6 (?) of the small HF versions all under one pan.

The things don't impress me much with humanly percievable mechanical vibration (I understand 30KHZ is dang fast).
They do a dandy job of getting hard or greasy crud off of clock gears and axles.

If it would work, at all, I figure the pan would have to be filled with water, and the battery set in the water.

Even the big ones are not very big.  Best I can tell, they are mostly made for jewlery cleaning.
Be kind of hard pressed to find a redily available, afordable, commercial version large enough for a 34AH class SLA.

I will try to remember to take a pretty bad 7.2AH-class SLA and a couple scooter (wheelchair scooter?) SLAs up on the next trip.
Can't hurt to try it.
G-

[scottsAI]

While on a conf call my APC SmartUPS 1000 started making a loud strange noise. Giving me notice the batteries were failing. While removing the two batteries 12v 12ah, noticed on the side “charge to 14.0v if cycled 14.5v”. UPS charging voltage is 13.89v (no batt). Battery ~5yr old.

Put a 23w load on battery, capacity 4ahr.
Charged with current limited 14.0v power supply.
Cycled twice.
Capacity picked up a bit. Seen this before, cycling a battery tends to remind it how to work again.
Figured 14v seemed better what would 14.5v get me?
Each cycle the capacity increased, 3 times up to 7-8ah.

Like many; if more is better... what does MORE get you?

Recharged with 14.5v, then boosted voltage to 15v.
After a while could hear a weak bubbling noise with ear placed on battery.
Watched for swelling using a caliper no change.
Not wanting to boil out the electrocute, terminated after 1 hour. (current had dropped, not zero)
Capacity now just below 10ah!
Charged again at 14.5v once charged, continued with 15v, stopped when current stopped dropping. Not very long.

Placed batteries back into UPS, been over a year, still passing self test at 60% load.
Saved me ~$50.

Since, tried this on a couple other SLA. Good batteries, took very little current after boosting voltage above 14v. No noticeable change in capacity. YMMV.

Have fun,
Scott.

[joestue]

most of the time by the time the UPS's get to me the batteries are completly toast.. in one case i applied several KV across the battery terminals before even registering milliamps of current... completely dried out.

* cant comment about the bubbling.. i only hear that after i inject water into them with a syringe.