Battery reconditioning. Current results.

[huldah]

I have 8 100 Ah, 6Volt, Chloride Powersafe 3VB11 batteries, manufactured 1999. Two were used for engine starting, the rest were kept charged, but had very little use.

They have all began to die. I accepted that they are old and ready for the dump, however, I decided to see if they could be rescued.

I bought a PIC battery Pulser from www.courtiestown.co.uk and, after topping one battery up, began to slowly charge and then discharge it @ 11 amps.

Initially the battery only took 30 minutes to drop to 10.5 volts. This battery now takes nearly seven hours to discharge, and, with my 2 amp charger, about three days to recharge. The discharge time is continuing to grow.

Only seven more to go!

Points arising.

Sulfated batteries have only a small amount of lead plate exposed, so even with my 2 amp charger, they can gas badly and spray out acid. I am now doing the initial charging via the discharge resistance. The vents are flame safe, and I now cover them with blue paper wipes, as this changes colour if contaminated with acid.

I initially tried to work on two batteries in series @ 12 Volts, using a 2 stage charger, This was hopeless as the weakest battery gassed while the other battery was poorly charged. The voltage was not sufficient to switch the charger.

 

[Plevier]

after topping one battery up,

Topping up? With water?

3VB11 is a valve regulated sealed lead acid battery intended to give a 10 year life in telecom or UPS standby applications (i.e. hardly ever being discharged). If you have pulled the vent out and added water and turned it into a flooded battery I'm not sure what the effects will be. SLA batteries are differently configured from flooded batteries with a different balance of positive and negative plate capacity. You seem to be getting interesting results so far but I suspect it may be short lived.

Not sure what you mean by this: Sulfated batteries have only a small amount of lead plate exposed,

 

[huldah]

Can't find the detail for 3VB11 batteries at present. They are filed somewhere. However, they are also suitable for heavy plant, oil rigs, and engine starting.

They do vent some gas. The glass mat certainly appeared dry, so a small amount of water was added. They are about 12 years old.

As batteries become sulfated so the available plate area must be reduced. A fully sulfated battery will not take any current. I believe this is the reason that they were gassing so badly. The small area of exposed plate was overcharging.

Once the improvements started, gassing stopped.

 

[Plevier]

Yes they are fine for those applications, but not for regular discharge. They were originally designed for British Telecom for standby. See http://www.enersys-japan.com/documents/telecom.pdf They are intended only to be substantially discharged in emergencies not regularly. Engine start is fine because discharge is so shallow.

They will not gas detectably with the correct charge regime - 2.27vpc @ 20-25deg i.e. 13.6V for a 12V battery. You should not boost charge. Full recharge takes some days although up to about 80% is pretty quick, they have good charge acceptance.

Perhaps I'm taking your words too literally but sulphation does not reduce exposed plate area. It reduces the convertability of the active material all over. Lead sulphate is the discharged condition of both plates. Charging should convert it to lead peroxide (pos plate) and spongey lead (neg plate). Sulphation simply means it is sticking as sulphate.

I can't comment on these pulsing recovery gadgets, they were not around when I was working on these batteries at the time of their introduction.

Even when new the glass mat appears quite dry. It is not saturated - if it is the gas recombination reaction does not occur. In manufacture they were made a little bit wet - still not saturated, a carefully measured dose - then given a once only formation charge (like a boost charge) which would cause gassing, distribute the electrolyte and finish them at the right level of saturation.

Having added water you are now running these batteries effectively as flooded ones and they will certainly gas especially if you boost charge, whether you put the vents back or not.

I really don't know how it will behave as a flooded battery. It wasn't designed to be one!

 

[Bosun Higgs]

One thing is for sure, you wont have changed the chrystalline lead sulphate back to the amorphous form, just blasted it off the plates and onto the bottom of the battery. So the battery capacity will never recover to the original level even though it recovers sufficiently to accept a charge.

 

[huldah]

Thanks for the interesting information. The batteries have always been kept charged, but, except for the engine start battery, not used.

I am keeping an open mind as far as the pulser is concerned.

There is one difficulty, I have got to plan seven hours ahead, to be home before the batteries discharge beyond 10.5 volts!