battery sulfation

[meep]

I've built and used/tested a few desulfators myself.

I think most of the public offerings are marketing/gimmicky.

It takes weeks/months for pulse desulfators to work. and they don't always work--- some batts can be too far gone.

The "gentle" one I built will pulse up to 60V if the battery is highly sulfated and the internal resistance is high. you need those higher V to be able to penetrate a badly sulfated cell. It's a very, very quick pulse, short-lived and filtered by mst vehicle electronics. BUT--- over time it did kill a small charger I had running parallel to it, as well as other electronics. It also PO'd the ECU on a late model jeep that I ran it on for 72hrs once. So--- disconnecting batt from vehicle and everything else is suggested.

I've personally seen it work, and not work--- and I do think it's poorly marketed and generally not well-understood by the consumer. Read up on the theory and real-world feedback and reviews before you commit.

 

[SHOZ]

Also the sulphation is not converted but shed. The accumulation at the bottom of the cell is minimized anymore for the way the plates are wrapped but it still is less active material. Nothing will change the sulphated lead back into active lead.

 

[Donald]

Well - its worth an experiment over the winter. I have the extra batteries and BatteryMinders.

But the comments lead me to a follow-on question. When one has a "shorted cell" is that because of failed separators or a pile of sulphted lead particles that is high enough to touch the bottom of the plates?

 

[SHOZ]

If the separator is shorted, it has a hole in it, more than likely caused by sulphation and the growing sulphate crystals are touching between a positive and negative plate.

If the sulphation is shed and accumulates enough at the bottom this too will cause a short.

The old school batteries used sheet separators of a rubber/fiberglass mix. Newer ones use a mico porous rubber envelope that also covers the bottom of the plate, helping to insulate from bottom shorted cells.

AGM batteries use a nano tubular form of fiberglass mat. It is cut longer than the plate and will close up at the bottom with the mat from the adjoining plate.

 

[JHZR2]

Originally Posted By: Donald
Well - its worth an experiment over the winter. I have the extra batteries and BatteryMinders.

But the comments lead me to a follow-on question. When one has a "shorted cell" is that because of failed separators or a pile of sulphted lead particles that is high enough to touch the bottom of the plates?


Material is shed from the cells, sulfation or not, during cycling... THis creates a conductive sludge at the bottom of the cells, which ultimately creates a fairly high impedance short.

I have to wonder if it cannot happen in AGM...

 

[SHOZ]

The AGMs with the mat will compress the cell. There is no free liquid. This traps the microscopic lead particles right where they are.

What usually fails in an AGM battery is either the lead strap that ties all the same polarity cells together, the actual lug from the individual plate to the strap of the lead paste will separate from the lead grid. But this is true for most batteries.

 

[JHZR2]

Originally Posted By: SHOZ
This traps the microscopic lead particles right where they are.


That's what I figured...

Also this has been discussed before and has become famous by other sites!!

http://www.impactbattery.com/blog/2013/02/battery-desulfators-do-they-work/

 

[JHZR2]

Interesting... Some insight of the behavior. The batteryMinder patent also gives info as to how these circuits work.

http://www.fusselman.org/wp/2010/11/18/the-desulfator-debacle/

http://forums.woodalls.com/index.cfm/fuseaction/thread/tid/22248572/srt/pa/pging/1/page/1.cfm

 

[meep]

Originally Posted By: SHOZ
Also the sulphation is not converted but shed. The accumulation at the bottom of the cell is minimized anymore for the way the plates are wrapped but it still is less active material. Nothing will change the sulphated lead back into active lead.


Not sure if this is right ^^^?

When battery is discharged, the sulfur ions come out of the sulfuric acid and actually attach to the battery plate. The electrolyte, having lost some of its sulfur ions, loses some of its acidity, and more plain water at the same time. (That's part of why a completely drained battery basically becomes water and can freeze at the whereabouts of 32F, whereas a charged battery must be much colder). When a battery is charged, the process reverses, sulfur is pushed back into solution.

A completely sulfated plate is very difficult to revive, which I think is what is meant in the quoted post.

The only time sulfur is "shed" is when the plate material itself weakens and a chunk falls off. That is irreversible, as without connectivity to the plate being charged, there will be no motive force to push the sulfur back to solution.

 

[JHZR2]

I think what is implied is that the sulfate crystals can be like little dendrites or formations which create a surface roughness compared to a properly cycled lead plate. As a result, some can fall off.

 

[SHOZ]

The battery plates in industrial batteries are around 1/4" for the pos and 1/8" for the negatives. This is compared to playing card thickness on auto start batteries.

We tried for years to come up with a desulfating regime for older batteries using both chemical and electrical methods. Never found one that would work long term. It may shock the battery into working for a while but in the end it is really at the end of it's life.

Usually what I have seen is pushing too high a voltage because of sulfation and the negative plate just falls apart. And the positive plates turn to mush.

But YMMV....

 

[JHZR2]

Yes but Pb-acid isn't like Li-ion where ions are intercalating into a 2D or 3D matrix. It is entirely a surface reaction. The shedding should be a function of surface area, and while sure, the industrial stuff has bigger, heavier plates that make a difference because they can shed more, at some point you shed enough to create an internal short, and then it is irrelevant anyway...

 

[Donald]

OK, my desulfation test has started. The 750 CCA battery is in my basement and its current CCA is 592. Its connected to a model 2012 BatteryMinder. Its a group 27 battery with caps.

 

[JHZR2]

Can you take pictures down into the cells?

Too bad we dont know the impedance, at least let us know the case temperature when you take measurements.

This will be an interesting test!

 

[meep]

Ditto that. Interested!!!

 

[Donald]

I will see what I can do with pictures. The case temp should be basement temp, which is unfinished but gets spill-over heat from the oil boiler.

 

[dailydriver]

How well sealed is this basement from the upstairs (living) floors??

The stuff coming out of actively charging/desulfating lead acid batteries is NASTY, EXPLOSIVE, and DANGEROUS/TOXIC!!

 

[Errtt]

I've used my BatteryMinder 12248 on a couple batteries that I didn't think would come back to life, but they did and those batteries are still in use.

 

[Donald]

OK, today the CCA is up to 612. The Solar tester no longer says its bad.

Yesterday it had been in my basement for about 5 hours warming up a little when it read 592. Now its been in the basement 30 hours.
Its possible it warmed up slightly between yesterday and today although I was thinking the 5 hours should have done it.

First picture. The brown/tan should be much more black or dark gray I believe.



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[Donald]

CCA at 636 tonight.