Lead-acid battery desulfating 2

[markmc]

I would like opinions on equipment designed to desulfate lead-acid batteries. I have read as much as I can find on the subject. There are a few companies that manufacture charger/desulfaters. The claim is that by applying a pulsed signal (1 Khz?) range, the formation of sulfate crystals which naturally occurs over time is retarded or even reversed, hence extending the life of a battery or reviving a "dead" battery as long as it doesn't have a shorted cell. Would anyone more knowledgeable than me like to comment on the viability, limitations or drawbacks of this technology.
Thanks
Mark

 

[gezcooke]

Typically when SLA batteries are stored for a long period of time lead sulphate is formed on the negative plate of the cells. Keep batteries on a nice warm shelf (say 35 degrees) and the process can take as little as three months or so. Similar effect happens if you leave a battery deep discharged for a length of time.

However, sulphated SLA batteries that are from a reputable stable (i.e. the ones that actually weigh a bit, have real chemicals and lead inside and aren't 30% of the size/weight of the competition) can be recovered by careful steps.

Firstly, the sulphate layer increases the internal impedance of the battery to the extent it won't accept a normal charge. Trick here is to apply a much higher charging voltage to start to get some current to flow to break down the sulphate layer. Now the associated problem is monitoring for signs of runaway because once you start breaking the layer down the current will start increasing pretty quickly.

With the current market climate there are mountains of SLA cells all around the world that were bought in for internet farm applications and have yet to be installed. Left in the warm for 6-9 months and the sulphation will be excessive but if kept in the cold (0 degrees C)then you can get up to a year storage.

In summary there is no need to build anything too clever - apply high voltage (typically double normal CV charge), watch for the current to rise indication the sulphate is breaking down and then drop back to more conventional charging. Suggest cycling the battery a couple of times afterwards and if internal resistance is back inside limits then battery should be good to go.

 

[GOTWW]

I have used the pulse desulfators on 220Ah 6-volt golf cart cells. You install them to the batteries and they have a little led that blinks. From an ammeter standpoint it appeared that they would inject a current pulse at ~60-100 times per minute. Should have taken them to the lab and shot a oscope capture.

It is hard to say if they did much good. I gave them away to a freind with a weak array and sadly abused bank of batteries. In this case I believe they actually helped the lifetime of the cells. I say this because they finally replaced the old cells with a new set, and no pulsers. (the pulsers died because of the incidental acid from the old batteries) they looked like they were potted well, but that sufferic acid is nasty stuff.

Anyway the new set of cells were badly sufated and useless after maybe one month. It is tough to train people with no electrical background. They constantly refer to the hydrometer readings that indicated the cells are fully charged.

I think I have trained them about the equilization process. Their batteries seem to be doing better now.

 

[SimonWiles]

Testing of battery desulfators.
I am currently doing some testing that should clearly confirm if the desulfators work or don't work.
Preliminary work is promising.

 

[felixc]

Hey SimonWiles, keep us posted with your results, this is good stuff for the forum!