Guess What Will Happen: Battery Desulfation Experiment

[CatalinaWOW]

Don't let OPs problem with the Radio Shack batteries turn you away from some smoking deals.  Happened across a Radio Shack that was still open and closing out and got 3 7AH units for $12 each.  When I got them home found all were good. 

[ReaDave]

Hi everyone,

Just found this forum and this topic which has me very interested, particularly the stuff about reverse charging SLAs at 2% to remove sulfation. I have a bunch of SLAs that were given to me by a friend who owns a security company. They replace the batteries in their client's alarm systems every year whether they need it or not and he gave me a bunch of the old ones which have been quite serviceable. Many of them now have significantly shorter AH capacity so I'm going to give this technique a shot and see what happens. Worst case scenario is that I gain nothing much. The batteries cost me nothing so any potential gain (pun intended) is a bonus.

For those who are curious, I just posted a short intro HERE along with a little at the end about how I found this forum.
This looks to be a very cool place for a fellow electronics geek!! 

[ReaDave]

I've just set up an LM317 current limiter running from a 12 volt unregulated plugpack (no load is about 16 v) and even with quite a large heatsink, the 317 gets quite hot no doubt because of the voltage drop across it with a reverse connected, partially charged battery.
I have the current set to just under 130 mA (battery is 12 v, 7AH).

I'm going to set up a 2N3055 pass transistor (probably overkill but I have a bunch of them lying around) to relieve the load a little on the 317.

[oldway]

They replace the batteries in their client's alarm systems every year whether they need it or not ...

It seems a little overkill...With no break's, we replaced such low capacity batteries (with fast-on connectors) every two years.

the stuff about reverse charging SLAs at 2% to remove sulfation.

As far the battery is not completely discharged and voltage polarities of the battery are not inverted, reverse charging is the same as discharging the battery.
Why use a LM317 to do this ?
You can use a simple power resistor or an incandescent bulb.
But I do'nt agree with this: completely discharge the battery will not desulfate the battery, nor charging with reverse polarities, it will only make the situation worse.

[eneuro]

But I do'nt agree with this: completely discharge the battery will not desulfate the battery, nor charging with reverse polarities, it will only make the situation worse.

I do want keep battery at safe volatge levels during desulfation and charging, so added in my desulfator prototype monitoring of input voltage pulse and battery voltage to triger switch in this based voltage multiplier desulfator when those voltages are at proper levels, so it will stop desulfation/charge if battery voltage will be above its floating voltage (will resume later when goes down or slightly discharge battery) or wait for input pulse voltage to be above lets say 10.5V, so another battery can be used as power source if someone wants to experiment more 

So, far less than 1KB of AVR ATTiny85 code and it looks like this small monster will make this desulfator/charger smart and allow remote monitoring of battery for more scientific approach to investigate desulfation
It could be nice to measure battery internal resistance from time to time, so maybe adding power resistor and mosfet switch will be good idea and additionally it will let us experiment with discharging battery from time to time, so if we can charge/discharge we can implement many interesting desulfation schemes 

[eneuro]

Reused optoisolated gate driver prototype in desulfator project, so was able connect everything together

Unfortunatelly in a hurry connected car battery... in reverse on right side of desulfator-hopefully caps didn't exploded 

Just trying figure out why in circuit like above (100uH 2A , not 1mH)  those 50V   2x 470uF in parallel caps only got very hot in a few seconds when -12V old car starter battery applied in reverse, but they still looks like brand new, however didn't desoldered them yet to test alone   
No caps "magic smoke"  why?

Update: There is some hope, but 15% of 50V is only 7.5V, so probably no chance those two caps survived  -12V reverse polarity
digikey: Reverse Voltage

IEC 384-4 (Solid or Non-Solid Aluminum Electrolytic Capacitors) and IEC 384-18 (Solid or Non-Solid Aluminum Electrolytic Surface Mount Capacitors) specify that capacitors can withstand the following test conditions. After 15% of the rated voltage (derating the voltage at the maximum operating temperature) is applied for 125 hours in the reverse
polarity direction, and then, the rated voltage is applied for another 125 hours in the forward polarity direction at the upper category temperature (maximum operating temperature), there shall be no significant capacitor damage

BTW: I had of course protective glasses 

[MrAl]

Hello there,


Some things that in theory seem possible are just too complicated to actual get to work in real life.  The Space Shuttle was scrapped even though it worked to some degree, time travel is theoretically possible but no human can do it today.

In the case of the 'desulfator', the nature of the failure has to be understood first.  If the battery is dry inside it will never work again no matter how long we leave in on the 'desulfator' because it needs liquid to work as well as new plate surfaces.  So the liquid level is one measurement that has to be done first, but there are probably other measurements that have to be done in order to vary the process well enough to get anything useful to happen.

Is it even possible to remove anything on the plates electrically?  We all think it is possible, but what if the pulse width has to vary with say the thickness of the material that is covering the plates?  What if it also has to be extremely slow, so slow that it takes a year to do correctly?
I bring this up because the process is a little like 'mixing', where we have a solution that separates over time and we'd like to mix it back together again (such as paint) using vibration.  Can we do it with just two electrodes and some current?   I dont think so, but even if we physically vibrate the container we have to know what frequency to vibrate it at.  If it is too fast it will actually cause more settling or else just not do anything at all, even though we leave it there for a week, vibrating constantly.

So if this is to be done at all, we have to know each and every physical parameter that affects the 'desulfating' process so we know how to vary the drive mechanism properly.

I built a 'desulfating' circuit a while back, used it on a 6v lead acid cell.  Left it on for days and it maybe increased the charge a little bit.  It was built from a microcontroller and a very high current MOSFET for the switching, and had high value capacitance to ensure a high current pulse was sent through the battery.
The battery was only used about 6 months prior to that and showed signs of what we call sulfation.

My confidence in this working with out much more research is so low that i have to put the word 'desulfator' into quotes every time i want to say it :-)

If someone can suggest a safe and not too difficult way to disassemble a lead acid battery (small sealed type) and place it into a clear plastic case, i'll try doing it again and observe the surface area of the plates and see what happens.

[oldway]

It seems sure that the electric desulfation works, at least partially.
This is proved by tests demonstrating the recovery of a portion of the capacity after electric désulfation.

But it lacks clear scientific explanations and demonstrations to prove it.

The first problem is to verify if the loss of capacity is due to sulfation or to other cause.

There are indeed other possible causes for loss of capacity as corrosion or active material that frees up from the plates and that fell to the bottom of the battery or of the envelope.

If it is caused by sulfation, you must also check in what circumstances sulfation happened.
- Progressive sulfation during normal use.
- Total sulfation after prolonged total discharge.

Both cases are not the same.
In the first case, only a part of the plates is covered by sulfate and this layer is thick and irregular.
In the second case, all plates are covered by sulfate of a substantially uniform thickness.

How does the electric désulfation works?

Certainly not by the fanciful theory of resonance of lead sulphate crystals that would break under vibration ...
It is a scientific nonsense that only those who knows nothing about chemistry and science can believe.
This theory is based on the piezoelectric characteristics of crystals.

The objections are:

- The deformation of a crystal depends on the electric field to which it is subjected.
Now, the pulses generated by electrical désulfators cause only a small change in voltage at the terminals of the battery, and therefore the electric field is low and insufficient to cause a significant deformation of the crystal.

- The resonance frequency depends on the dimensions of the crystal. They are different from one crystal to another.
For a resonance and amplification of vibrations, there should be applied a constant electric field of a frequency equal to the resonance frequency of the crystal.
Pulses only generate damped oscillations.

- It is very difficult to break a crystal (or perhaps impossible) by piezoelectric effect in the air.
The electrolyte dampens the oscillations, it is obviously impossible to break lead sulphate crystals under these conditions.

- it would be easy to reproduce this and to shoot it if it really would be possible.

This theory is pure bullshit ...

One finds no valid scientific explanation on the Internet.

[eneuro]

It seems sure that the electric desulfation works, at least partially.

We'll see 

Anyway, it looks like those two caps 50V 470uF caps reversed for a few seconds with -12V doesn't seems to be damaged 

Just made charge & discharge test and got the same time around 64s of discharge from 24.8Vmax to 1.0V via 21k resistor like with another two caps never reverse powered.
Expected they are shorted, but it looks like they blocks DC voltage and 12VDC 5W light bulb isn't shining in my eyes, discharges in the same time like brand new ones, so those caps doesn't looks like damaged ones   
Now applied 25V voltage via this light bulb to limit current in the case of short circuit and will leave them for many hours to see if it works, but while it is desulfator prototype will let it go with those caps and additional fuse of course on battery side 
Probably it will be good idea to add a few lines of code to allow changing desulfator frequency on the fly using potentiometer during first tests-starting from 1kHz to 10Khz 

If desulfator will not work... it will be of course ONLY due to those reverse powered caps on battery side 

BTW: Yep, those caps looks like have close to its nominal capacity when entered experimental data into derived formulas for capacity we get experimental: ~950uF, while 2 x 470uF is 940uF theoretical +/- tolerance, etc, close to those caps specs 

Code: [Select]

Vo= 24.8V
Vc= 1.0V
t= 64s
R= 21k
C= 0.000949 F ~ 950uF

[Fraser]

It would be a good idea to create some 'test cells' that could be visually inspected during desulphation experiments. What I would suggest is the removal of the six individual cells from a sulphated battery. The individual cells are then placed in their own test chambers that may be observed with a strong magnifier or microscope (better choice). The behaviour of the battery plates could then be monitored directly and adjustments made to the treatment regime to determine which works best.

Personally I would start with the convenience of a 2V lead acid gel battery commonly used in alarm bells and Radio Control Glow Plug engines. The cell can be easily extracted from its shell and reinserted if required. I would also prefer working with a sulphated wet lead acid car battery during testing as it removes the issue of dried out cell mats.

Experimenting with the plates sealed inside the battery is working blind and so difficult to monitor.

It goes without saying that working with Sulphuric acid requires suitable safety precautions and correct handling.

Cutting around a Gel battery top weld releases the cells from the case.

Am I interested in doing this? Nope, as already stated, I no longer have an interest in recovering knackered lead acid batteries. Life is too short already 

Aurora

[eneuro]

Experimenting with the plates sealed inside the battery is working blind and so difficult to monitor.

Internal resistance should improve as well as capacity in desulfated battery, so it can be tested.
Anyway looking for small visual camera with small optics to put it in glass housing inside battery cell to spy those plates surface changes in real time 

First run through light bulb at 8kHz ~5us ON ~4% duty cycle and... looks like current flows and energy disipated on battery side however not sure into which direction 

Tried also without light bulb and nice a few kHz sound, so something is going on there 
Implemented in MPU that PWM pulse will be send only when voltage on caps on transformer power side will be higher than battery voltage, so there is no chance that battery charges this power side caps when switch is turned on.
No time today for futher investigation and current/voltage scope waveforms, etc-need to simulate this thing at higher frequency than 1kHz to see what to expect, but nothing  and energy disipation on battery side cleary visible at least in light bulb, which was added to simulate higher battery internal resistance and to limit output current in first runs of this desulfator

[oldway]

We'll see 

The fact that it seems sure that the electric desulfation works does not mean that any desulfator will work.

We should first understand how the electric desulfation works to project a correct device.

Surely, this can't not be based on the stupid principle of resonance of lead sulfate crystals.

As I said before, professionals desulfators produce high current pulses (of the order of 50A peak for a 100Ah battery) of approximately 200 ms every 3 or 4s.

This is my personal theory about that.

For sulfated batteries after a long deep discharge, internal resistance becomes very high and the battery will not accept the charge.
- The acid is transformed into sulfate during the discharge and the electrolyte becomes almost pure water.
The electrolyte is then a poor conductor of electricity, which greatly increases the internal resistance of the battery.
- The sulphate layer is insulative and prevents current flow.

According to my tests, at least part of the battery capacity can be recovered  by initially charging the battery with a much higher voltage (30 or 40V for 12V battery) but by limiting the current to about 1A by a serial power resistance. (22R 25W)

Once the voltage across the battery drops to 12V, it can be recharged with a normal charger.
I do not know if we can recover the full capacity of the battery that way.

For batteries sulfated in normal use, manufacturers recommend charging flooded batteries with a higher voltage for an hour each week as a preventive maintenance.

To eliminate this sulfation, the problem is to dissolve the crystals of sulfate.
This is difficult, the purpose of desulfation is to get there by boosting the battery voltage for short periods.

You should know that:

- Sulfate is very little soluble in water, but a little more soluble in sulfuric acid.
- As the electrolyte is saturated with sulfate, it is no longer possible any dissolution of the sulphate.
- It is a slow reaction increasing with temperature rise.

[Fraser]

IIRC manufacturers suggest that deliberately charging a wet Pb battery at an elevated level will help to reduce any mild sulphation on the plates due to the vigorous hydrogen gassing that occurs (and associated & agitation of the electrolyte). Such 'treatment' is advisable only where any lost H2O may be replaced and where careful monitoring of the battery is possible. Deliberate excessive charging that causes large amounts of out gassing is not something that I would recommend unless you know exactly what you are doing. As a child of 10 I did something stupid with a 12V motorcycle battery ( I was collecting hydrogen gas in a bell jar !). There was a hydrogen gas explosion in the battery and it blew the case apart, covering me in dilute sulphuric acid and removing my eybrows 

Please be careful 

Aurora

[tautech]

IIRC manufacturers suggest that deliberately charging a wet Pb battery at an elevated level will help to reduce any mild sulphation on the plates due to the vigorous hydrogen gassing that occurs (and associated & agitation of the electrolyte). Such 'treatment' is advisable only where any lost H2O may be replaced and where careful monitoring of the battery is possible. Deliberate excessive charging that causes large amounts of out gassing is not something that I would recommend unless you know exactly what you are doing. As a child of 10 I did something stupid with a 12V motorcycle battery ( I was collecting hydrogen gas in a bell jar !). There was a hydrogen gas explosion in the battery and it blew the case apart, covering me in dilute sulphuric acid and removing my eybrows 

Please be careful 

Aurora

Warning noted 
A gassing charge proceedure has been around nearly as long as Pb batteries have and is a well known maintenence step.
Yes it must only be used if one can replace the lost H²O.

[SeanB]

I am reminded of a story about a large company, which used a large number of electric forklifts. It involved a smoker who lit a cigarette, next to the large room in which there were around 40 battery boxes being charged, which resulted in the destruction of all of them along with the room. He, along with the operators of the charge station, survived mostly intact. He still smoked afterwards, too thick to take heed of the warning.

[tautech]

I am reminded of a story about a large company, which used a large number of electric forklifts. It involved a smoker who lit a cigarette, next to the large room in which there were around 40 battery boxes being charged, which resulted in the destruction of all of them along with the room. He, along with the operators of the charge station, survived mostly intact. He still smoked afterwards, too thick to take heed of the warning.

The sparks from maintenence grinding near a battery charging can have a similar result.
Many a small commercial workshop has learnt this the hard way and battery areas should be well away from any engineering.

[oldway]

A big mistake that some people make: do not remove the caps during charging.
Another one: Do replenish with distilled water only after charging the battery, not before.
NB: If level is very low, you may add a little water.

[eneuro]

We'll see 

As I said before, professionals desulfators produce high current pulses (of the order of 50A peak for a 100Ah battery) of approximately 200 ms every 3 or 4s.

Not such a big deal output high current in voltage doubler based desulfator I've changed for even higher currents and added axternal power supply.

After playing more in circuit simulator quickly found a way to limit heating of battery side inductor and diode at higher switching frequencies and changed software to enable different operating modes including from self powered battery without external power supply-in this case we get classic voltage doubler desulfator described in linked posts above, but with battery undervoltage and overvoltage protection 
By adding additional current limit between higher voltage power side and battery, charging and desulfating possible at the same time and it doesn't affect output current spikes which are limited by wires inductance and parallel capacitors resistance.

Very nice a few kHz frequency noise close to desulfator battery side, similar to... piezoelectric buzzer, so it might destroy those bloody crystals if not by resonance, than like in spot welding by raw power 
Anyway this crappy multimeter gone crazy at 200V range when tried measure output voltage on desulfator battery terminals and showed... close to 90V 
 
It works now without any significant heat dissipation, but even with high short current pulse AC mosfets switch at a few percent duty cycle of course will not disipate too much heat as expected 
I have battery overvoltage protection implemented before high voltage pulse is send, so now it time add a few fans and let it go for more time to see if nothing gets hot and add I2C interface to monitor this thing from remote control room on laptop screens 

[Mosaic]

Sorry to disturb the old thread but here's something modern and tested that works. DIY  & open sourced. It is my design and it is tested over hundreds of batteries. I have data logs of many of them.
https://hackaday.io/project/25741-desulfator-engine-re-climate-change-mitigation

[floobydust]

Finally someone putting enough energy in to breakdown the sulfate crystals. I don't understand the chemistry involved but every desulfator I've built was a giant waste of time, peanut size pulses and then I realized it was snake oil.

It looks like you are using 36VDC 6,600uF capacitive-discharge; graph shows 640Apk into a Group 55 car battery, is that correct?

[floobydust]

Mosaic open-sourced his build and started a new thread here: https://www.eevblog.com/forum/oshw/desulfate-regenerate-lead-acid-batts-a-new-diy-guide-overnight/

[Dehv]

There's a research paper that's paywalled but indicates in the abstract a slightly  interesting variation on the theme, bringing down to 0 v then REPLACING TGE ELECTROLYTE and reverse charging at  CC for 24 hrs then back to normal polarity charging for 48.

Claims are to recover 80% of capacity.

[Dehv]

Found it. Attached: pdf

"RECOVERY OF DISCARDED SULFATED LEAD-ACID BATTERIES BY INVERSE CHARGE"

2009 original paper by Karami.

And a more comprehensive but I find not as practical expansion on the above work at the following

https://www.google.com/url?sa=t&source=web&rct=j&url=https://academiccommons.columbia.edu/download/fedora_content/download/ac:206709/content/Spanos_columbia_0054D_13754.pdf&ved=2ahUKEwjanIf1nb_0AhXrFjQIHWG2AmsQFnoECBMQAQ&usg=AOvVaw2e5UZOnEZztAd4oLA4p-qi

[Dehv]

In the karami pdf abstract it seems to state the procedure is to replace the acid with new after discharge, however nowhere in the rest of the document is that mentioned.

The other studies reference it as "according the procedure by Karami"

Without restating if acid is changed at any point.

Well ain't Dat a dill pickle.