Pb/H2SO4 bat'ries.

[mael]

[mael]

[SeaMonkey]

[mael]

When does one stop the pulsing?

I think the sulphation can be declared 'beat' when the SG of all the cells catches up with the cell with the highest SG.

This is on the assumtion that the dilution of the acid was the same for all cells.

Would I be right in thinking there may be a minor variation due to sulphates adhering to pieces of plate which have fallen to the bottom or are held in situ but no longer connected to the lattice/grid?

[SeaMonkey]

The pulsing can be stopped when the battery voltage exceeds 14 Volts and stops increasing.

Then, the battery should be discharged into a 5 to 10 Ampere load until the measured loaded voltage decreases to 10 Volts. This will help to "unclump" the newly re-formed active plate materials.

Then charge and pulse again until voltage stops increasing, and repeat once more.

Once it's been cycled several times it's nearly fully rejuvenated.

Yes, there may be some loss of S.G. and some plate deterioration because of shed material. When there is no further improvement in electrolyte concentration you may add more acid to bring it up to specs.

To keep the battery in top condition the pulsing, at a lower power level, may be continued indefinitely. This will counteract any tendency of the battery to sulfate due to self-discharge. This "maintenance pulsing" shouldn't develop any "heat" in the battery.

[mael]

[mael]

[mael]

[redriderno22]

just a small update

ive got another cart

going to try to referb the bats

ill post pics when i get a chance

[redriderno22]

[SeaMonkey]

[gandolflundgren]

Any updates on this? I wanna see how everything went.

[Ganapoes]

Sorry for the double post - It took so long to load I thought it'd got lost in cyberspace so I pressed it again.

[mael]

Although of course I don't know everything about lead/acid batteries, I would like to state how I feel about the process of bringing old batteries back into service.

There is no doubt in my mind that the death of a battery is the deterioration of the positive plates. The negative plates are likely to remain servicable for many, many years because they are basically solikd lead. But the positive plates are built using lead oxide on a lattice made from a hardened form of lead - but it doesn't last long.

On a practical note, I am sure it is easily possible to keep an SLI battery cranking for a decade - and maybe more. Though towards the end it'd better be on a car with an engine that starts easily because slowly those positive plates rot, and bit-by-bit those positive plates have less effective surface area.

The positive plates rot from the bottom up. I suppose this indicates it's probably due to the relatively high concentration of sulphuric acid in the bottoms of the cells due to the higher specific gravity than the less concentrated electrolyte nearer the surface. Stirring by applying a controlled over-charge occasionally might help this situation, as might manually moving the battery so as to mix the electrolyte. I gather some of the most expensive and longest-lasting lead/acid batteries are fitted with a pump which continuously moves and mixes the electrolyte, and that this pump is always 'on.' And those long^lasting batteries will have positive plates which are far-sturdier than the crap batteries mostly in the shops nowadays.

I am sure that desulphating the battery is never a bad thing. Desulphating using (my method) of pulsing will mean the battery will remain useable until those positive plates corrode away - and that could well mean a decade's use or more. So all-in-all desulphating is a great idea. an arbitrary 'battery' will have the life of two, three, four or maybe even more than the normal if it is periodically desulphated and the cells equalised through a controlled over-charge.

Batteries where I am are particularly suited to desulphating because so many people here only use the car for short hops or infrequently use the car, so they tend to sulphate. Batteries in the US, for example, where the car is used day-in and day-out on long drives - are unlikely to be a good candidates for desulphating because the problem with such batteries is likely not sulphation so much as the batteries being physically being worn-out!

- And to an extent, the mixing of (alleged) maintenance-free batteries and wet-batteries is causing some problems:-

M.Free batteries are charged to only 14.1 (or so) volts. This is not a full charge, and inevitably sulphation will arise as a result. More cars now seem to have the battery-regulating circuits set to suit MF batteries. - Though if you fully charge a MF battery it'll soon gas itself dry.

Me? I make holes in MF batteries and replenish the electrolyte with distilled water and they last probably a decade. But most everyone will just throw them away because the process of replenishing a MF battery is hazardous, heavy and dirty. (I can't blame anyone deciding they don't want to fool with a potentially explosive lump of toxic liquid and metal).

The batteries in the US where desulphating would be well-suited (I think) would be special batteries which are not available easily or cheaply that are sitting on under-used earth-moving equipment or classic cars - and boats are likely an area where desulphating would work well.

In my experience commercial desulphators are as good as useless. You need a really good whack with a sharp-edged pulse to do the desulphating in a reasonable length of time (my opinion of course).

* In a pinch you can try a spoonful of EDTA in each cell and afterwards manually adjust the electrolyte to compensate for the loss of effective (non-bonded) sulphur the EDTA rips out and sinks to the bottom. Also you can try a bit of mag-sulphate to get some more life out of a knackered battery. Both the above will poison your battery, but it'll do its job for a bit longer - and that'a a good thing.

I'm not at all disappointed to have found a limit on getting old batteries back in service - far from it! Pulsing to remove the sulphates will mean at least double the life from your batteries at least, and it doesn't cost much in the way of electricity to do it.

[Oliveber]

In the end it reads around 12.3 Volts.