Author Topic: Desulphation (Mad Science!) Experiments  (Read 5151 times)

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thunderhead

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Desulphation (Mad Science!) Experiments
« on: September 17, 2017, 12:11:25 PM »
It's been a long time since I last posted, but in the meantime (7 years off-grid in rural Ireland) I have learned a lot.

I have a theory that the process of desulphation is only a problem on one electrode.

The textbooks say that the process of charging a lead-acid battery is like this:-

+ve: PbSO4 + 2H2O -> PbO2 + H2SO4 + 2H+ + 2e-

-ve: PbSO4 + 2H+ + 2e- -> Pb + H2SO4

Now the problem is that the lead sulphate is supposed to form a non-conductive form which cannot easily be broken down.  My theory was that it might be easy to break down on one plate but not the other: for example, lead sulphate could become lead at the -ve plate but not become lead oxide at the positive plate.

The test for this is to try charging the battery in reverse.  If sulphation is equally a problem on both plates then it won't matter: they'll still not take charge.

Now, before we go any further, I should point out that I am a mad scientist by hobby.  I have been fooling around with things that corrode (including concentrated sulphuric acid) and things that go bang (including hydrogen) since I was thirteen -- over forty years ago!  If you don't know what risks are associated with abusing batteries, (and, to give you a better idea, try googling "acid burn face",) please take it from me that this is not something to try.  As they say in all those jackass TV programmes: DO NOT TRY THIS AT HOME!

Nevertheless, I tried it to see if my theory was true.  I had four old deep-cycle batteries that I bought from Halfords many years ago: they said 85Ah on them but, after I had abandoned them as too worn and then left them in the back of the shed for two years, they showed between  5Ah and 7Ah capacity.   I connected a bulb across each and discharged them flat.  I left the battery connected to the bulb for about a week each, and then connected each -- in reverse -- to a 40W solar panel and gave them about a week of Ireland's finest summer.

All ended up reverse polarity.  What is more, each could then be charged up to about 40Ah to 50Ah!  So each went back on the bulb to discharge flat, and then slowly charged up to correct polarity again.

Summer has gone here in Ireland, so I am charging them as I have spare electricity (through a 12v bulb in series with my dumpload) but one is already back up to 60Ah (and has been added to my battery bank,) and the other three should be added in a month or so.

Now, since you are not going to repeat my crazy experiments, why is this interesting?   The reason is that I believe I have demonstrated that sulphation is only a problem on one plate, and suggested how these desulphation gadgets are supposed to work.  The active part of the desulphation pulse must be the part where current flows in reverse direction.  That should help with desulphation circuit design.

I'm not going to have much electricity to spare until next summer, so I won't be doing any more mad science until then, but I hope that this knowledge might be useful to someone.
« Last Edit: September 17, 2017, 02:49:04 PM by thunderhead »

joestue

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Re: Desulphation (Mad Science!) Experiments
« Reply #1 on: September 17, 2017, 03:03:35 PM »
I believe it. I might try this with my truck battery which seems to be down to less than 10 amp hours capacity, but still works fine.

charging in reverse is going to turn pbso4 and pb02 back into lead, which is a good thing. the lead is what holds the entire positive plate together. if you can charge it slow enough to get that lead deep into the posititive plate, you've permanently increased the capacity of the battery when you charge it "forwards" and that lead is retained, holding the active material (pb02) together.


in my experience the positive plate expands and corrodes and litterally crumbles apart, well before the battery should have reached end of life.


the risk you would be taking would be permanent damage to the negative plate, as it expands and fills with lead oxide.
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george65

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Re: Desulphation (Mad Science!) Experiments
« Reply #2 on: September 17, 2017, 07:24:02 PM »

in my experience the positive plate expands and corrodes and litterally crumbles apart, well before the battery should have reached end of life.

This is always why I took these " Restore a dead battery " products/ devices/ gimmicks as hogwash.  You can't just add powder or a devise to a battery to restore physical Damage...... Or so I thought.
The other things is the lead that comes off eventually piles up on the bottom of the cells and the thing self shorts.
I guess it depends on the individual case but I have to wonder how much of the lead can be Re-deposited back on the plates? 
The other question would be how long is the restored battery life? Will you get another year out of it before having to do it again or will you get closer to original life?


Quote
  The risk you would be taking would be permanent damage to the negative plate, as it expands and fills with lead oxide.

If you are playing with an already dead and rejected battery, in my book there is no risk. Nothing to loose, something to gain.

I have played with a lot of batterys as well. Boiled them up, had them gassing wildy and of course blown them up. 3 times now and I have had the acid to the face.
Every single time I have blown a battery, it was NOT doing anything I should not have been, just charging them ( or not) normally.  First one that went off I was about 20.  Had taken the battery out of the car and sat it under the workbench.  I dropped a shifter which landed right across the terminals. Must have been some gas venting because the entire top of the thing went straight up followed but a rush of acid. I had looked down to see the shifter fall but managed to close my eyes maybe in reaction to the sound before the acid got me.  Run for the garden hose, Clothes ruined like a swiss cheese, I was OK.

Next one was charging a battery with the caps off and again managed to drop something that hit one of the clamps on the  terminal and knocked it off. Must have sparked and whooshka. Blew the thing to pieces. Saw the bit of metal falling and turned away before it hit but was nearly deaf for about 3 days.

Last one was about 2 years ago. Had a battery from my 4WD which was a very large and quite new one on charge as I replaced the alternator.  I'm pretty sure that must have been faulty. Was no where near charged and only on a 2.5A charger.  I had it sitting on the ground down from where I was standing, ( had just walked up to the bench with something) when the thing again blew apart like a bomb.  Scared the crap out of me because I had not touched the thing or come within about 3 ft of it.  Daughter was sitting on the back verandah and looked up in time to see me throw myself into the swimming pool in the middle of winter fully clothed and stay down a long time.

I caught a piece of plastic in my leg which I didn't even feel till my daughter pointed out as I was trying to get my jacket off. The blood was running down my leg  quite well. Pulled the plastic out and then it hurt like a bitch.  It slowed bleeding in the shower but was a nice deep 2" gash. Bandaged it up and it was fine apart from the pain. Don't like stitches.

Just annoys the crap out of me that every time I get hurt, it's innocent. I do all manner of stupid $#|+ where I am expecting to get my butt smacked by the hand of the " You should not have been doing something so stupid or dangerous" god but nothing EVER happens.  Come out the shower in the lounge room where mrs throws me a t Shirt from the washing she is sorting and nearly loose a thumb as I pull it over my head and stick my hand in the ceiling fan. Play with an induction generator doing 500V+ and work on live terminals, nothing.  Finish up and walk out the shed looking at something and knock myself out on the roller door I didn't push up far enough and wake up 5 min later looking at the sky and wondering how I got flat on my back on the floor?

If I got hurt Boiling batterys or playing with DIY burners doing 600KW and throwing 8ft flames I'd say Fair enough, serves myself right but it's always something like slipping on wet grass and doing my knee a month ago ( that still hurts like hell) where I has hobbling for a week that is what gets me.

I just moved here and cashed in a heap of dead batterys. I'll have to give this a go next time I get one. Think the battery in the ute is getting a bit ordinary so that may be the first test.
Question I have though is how can you tell a battery is sulphated or when it's died from other causes and what apart from internal shorting and breaks in the connections can there be?

I think I'll charge the batterys in a wooden crate on it's side with the open side facing a wall or into the yard. The crate would then be completely ventilated and act like a blast shield should another want to become a firework on me. Of course the fact I would be doing something risky would also mean nothing will happen to it at all.  ::)

joestue

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Re: Desulphation (Mad Science!) Experiments
« Reply #3 on: September 18, 2017, 04:05:10 PM »
A sulphated batter will have low specific gravity. A low capacity battery will have a lot of lead oxide that is electrically disconnected( mostly) from the positive plate.

George your experience with exploding batteries can be partly explained by the internal spark hazard from the broken plates reconnecting...
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thunderhead

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Re: Desulphation (Mad Science!) Experiments
« Reply #4 on: September 18, 2017, 04:29:21 PM »
Question I have though is how can you tell a battery is sulphated or when it's died from other causes and what apart from internal shorting and breaks in the connections can there be?

The obvious way to tell is that a sulphated battery shows a normal voltage (e.g. 11.8v - 12.8v or so) but only a tiny capacity.

Batteries that have shorted cells will show a lower voltage, because one cell is shorted out.

The batteries I tried this on were not starter batteries, but leisure (deep cycle) batteries.  These are constructed more solidly inside, and might well deteriorate in different ways.  In all four cases, though, they showed full voltage -- just hardly any capacity.

How long they will last ... I'll know by springtime.  :)


joestue

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Re: Desulphation (Mad Science!) Experiments
« Reply #5 on: July 06, 2018, 02:40:39 AM »
Periodically i can get UPS batteries for free. the last batch of batteries were 5AH AGM cells float charging at 13.5 volts in a 70F environment for 5 years. they are sigmastek, from batterysharks. one or two of them went open circuit and failed during discharge, a third one leaked a little bit i believe but can't prove it (they are mounted on their side and i can't remember if i cleaned out the battery tray 5 years ago). 10 in series for 120 vdc. 7 of them have replaced my truck battery in a 4.3L s-10 for the last 6 months or so, they seem to have enough capacity to crank the engine for 30 seconds, which is marginal but good enough for me.

another batch of 5ah 12v batteries that had similar use case as the others, but are potentially from 2006, have been float charging ever since. they measured 13.2 volts open circuit when i had them sitting on the ground outside for about 6 months. i believe i discharged them through a 100 watt 12v lightbulb and they held up 11 volts or so. anyhow, after 6 months they still measured 13.2 volts but no capacity. could short circuit them and no significant current. milliamps.

so i tried charging them backwards. for a few minutes, perhaps tens of minutes there was no significant current flow into the battery. then some of them started getting hot. internally hot far faster than i was pushing current into them (backwards). Two out of 8 got hot enough to burst some of the cell dividers. they remained hot for some time, hot enough to burn your fingers.

i don't think they shorted out internally because when they were getting hot they decided to go from -15 volts back to +11 volts or somewhere around there.

so something was going on. anyhow, some of the others that didn't burn up had hot spots which is indicative of broken plates, so i threw them all away.
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Ungrounded Lightning Rod

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Re: Desulphation (Mad Science!) Experiments
« Reply #6 on: July 07, 2018, 03:08:09 AM »
... after 6 months they still measured 13.2 volts but no capacity. could short circuit them and no significant current. milliamps.

so i tried charging them backwards. for a few minutes, perhaps tens of minutes there was no significant current flow into the battery. then some of them started getting hot. internally hot far faster than i was pushing current into them (backwards).

Sounds like your batteries were still charged - but with a layer of sulphation on the surface of at least one of the plates.  Good (or decent on all but one cell) voltage, but high resistance.

Thunderhead's approach left a small load on his cells until the whole of each plate was discharged - both + and - plates essentially solid PbSO4.  Then he charged them backward, turning the lead sulphate on the positive plate into lead and on the negative plate to lead oxide - the reverse of the usual situation (and usually a good way to break up the plates and kill the battery).

Story goes that sulphation is irreversible after a while because led sulphate goes through three forms with time.  First it's amorphous.  Then it forms a crystal structure that is difficult, but not impossible, to react back to lead - or to lead oxide - with electrochemistry.  Then, over a few months, it changes to another structure that is flat out impossible (or nearly so) to react (and which also may mechanically break up the plates as the crystals become large).

Thunderhead assumed that it's actually only ONE of the two reactions (to lead or lead oxide) that's not possible on the last crystal form - and that, by reverse-charging the battery somewhat, he can break up the crystals and get their material back into service.  (Let's presume he's right...)

But you didn't first fully discharge the plates.  Instead, you reverse-charged them when there was still a large forward-charged mass under a layer of the crystalized lead sulphate.  So what you did, on the hard-to-react plate, was to convert the skin of lead sulphate to a plate of the opposite type.  Your reaction started on the surface and worked inward, reducing the thickness of the sulphate insulating coating.  Eventually the insulation layer became negligibly thin and the reverse-charged layer broke through.  Now you had a single plate with layers that were charged each way, connected across, first the break-through hole, then eventually across the whole surface.  That's a fully charged cell with the two sides shorted by a VERY large connection, discharging itself rapidly.

It got hot?  I'm surprised it didn't explode!

Quote
another batch of 5ah 12v batteries that had similar use case as the others, but are potentially from 2006, have been float charging ever since. they measured 13.2 volts open circuit when i had them sitting on the ground outside for about 6 months. i believe i discharged them through a 100 watt 12v lightbulb and they held up 11 volts or so. anyhow,

And here you did it again - the batteries (or the portion of their plates that isn't stuck as crystalized lead sulphate) are nearly fully charged, because you didn't let them go until they had zero unloaded voltage.

Quote
Two out of 8 got hot enough to burst some of the cell dividers. they remained hot for some time, hot enough to burn your fingers.

Same mechanism as before.  But then, if a cell divider really ruptured enough to connect the electrolyte in adjacent cells, you have ANOTHER form of shorted cell:  With the electrolyte connected you have a charged plus plate from one cell connected by a thick hunk of lead to the charged minus plate from the other cell, immersed in the same electrolyte bath.  LOTS of power there.

Quote
i don't think they shorted out internally because when they were getting hot they decided to go from -15 volts back to +11 volts or somewhere around there.

And I tend to agree - on all but maybe one of the cells.  Once the insulating layer was reacted to opposite-plate type and the two layers shorted, the plate discharged until it the reverse-charged part and a corresponding forward-charged part were discharged, leaving the remainder of the forward-charged plate (and ditto on the equivalently-charged plate on the other side).  +11 volts might be an all-but-one-cell battery, with the missing cell corresponding to a ruptured separator taking a pair of plates out of service and making a single cell out of the remaining two plates and the two cells worth of partly depleted electrolyte.

joestue

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Re: Desulphation (Mad Science!) Experiments
« Reply #7 on: July 07, 2018, 04:20:40 PM »
these batteries had been float charging so long there is no liquid electrolyte inside them. when two of the batteries got hot, they got hot enough to bubble out from the case and break the connection between the outer shell and the cell divider. but i don't believe they had enough liquid in them to short out one cell to another, and they had 11 volts on them while they were very hot. the whole battery fairly uniformly was similar temperature, not just one side where the cell dividers let loose of the case. anyhow i really didn't notice or hear any of the valves open to release the gas, so i think the battery got hot enough that the plastic was so soft it bubbled out (i think the valves let gas out at 5 psi internal)

anyhow the point being some chemical reaction went on that caused internal heat to be dissipated in excess of the total amount of power that i pushed into the cell.

another issue here is the calcium oxide layer that forms on the positive plate between the grid and the active material (this is actually a better explanation than sulphation due to self discharge). charging the battery backwards would likely puncture through that layer which would liberate calcium sulphate which apparently is already added to the positive plate to increase discharge performance specifically at low temperature

here's another interesting paper i just found
http://cecri.csircentral.net/2081/1/22-1988.pdf
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thunderhead

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Re: Desulphation (Mad Science!) Experiments
« Reply #8 on: July 08, 2018, 09:32:22 AM »
... after 6 months they still measured 13.2 volts but no capacity. could short circuit them and no significant current. milliamps.

so i tried charging them backwards. for a few minutes, perhaps tens of minutes there was no significant current flow into the battery. then some of them started getting hot. internally hot far faster than i was pushing current into them (backwards).

Sounds like your batteries were still charged - but with a layer of sulphation on the surface of at least one of the plates.  Good (or decent on all but one cell) voltage, but high resistance.

Thunderhead's approach left a small load on his cells until the whole of each plate was discharged - both + and - plates essentially solid PbSO4.  Then he charged them backward, turning the lead sulphate on the positive plate into lead and on the negative plate to lead oxide - the reverse of the usual situation (and usually a good way to break up the plates and kill the battery).

Story goes that sulphation is irreversible after a while because led sulphate goes through three forms with time.  First it's amorphous.  Then it forms a crystal structure that is difficult, but not impossible, to react back to lead - or to lead oxide - with electrochemistry.  Then, over a few months, it changes to another structure that is flat out impossible (or nearly so) to react (and which also may mechanically break up the plates as the crystals become large).

Thunderhead assumed that it's actually only ONE of the two reactions (to lead or lead oxide) that's not possible on the last crystal form - and that, by reverse-charging the battery somewhat, he can break up the crystals and get their material back into service.  (Let's presume he's right...)

That is exactly right: I left a 55W bulb connected to them for about a week before attempting reverse charge.  At the end of that time the voltage shown on the terminals -- without load -- was millivolts.

For what it's worth the four batteries I did last summer overwintered quite well.  They seem to be performing like, well, normal batteries.



Ungrounded Lightning Rod

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Re: Desulphation (Mad Science!) Experiments
« Reply #9 on: July 09, 2018, 08:44:03 PM »
I left a 55W bulb connected to them for about a week before attempting reverse charge.  At the end of that time the voltage shown on the terminals -- without load -- was millivolts.

For what it's worth the four batteries I did last summer overwintered quite well.  They seem to be performing like, well, normal batteries.

Great!

As I read it, what you did to your (85 Ah) rated batteries was:
  • Discharge to zilch at 5A or less over a week or more (including some extra time to insure things were really flat)
  • Reverse charge at 4A in 7 daily increments of about 40 Ah (presuming a 5 solar-hours rating for summer in Scotland), producing a slow (and reverse) forming charge of 280 Ah, about 3.3 times the rated capacity.
  • Discharged into a load and rechargedf (that panel again?  or something else?) a couple times to estimate capacity.
  • Discharge to zilch at 5A or less over a week or more (including some extra time to insure things were really flat)
  • Trickle charged them forward through a bulb (with an unspecified wattage), probably less than 4A and less than 5 hours per day.

It will be interesting to see whether/how that can be simplified and/or optimized.
  • Are the sleep periods in the reverse forming useful?
  • Can we take out the "test while reversed" cycles or do they do something useful (like break up bigger crystals)?
  • Can the forward charging and reforming go faster?
  • Do additional discharge-and-slow-recharge cycles in the forward direction help with the battery reforming?
and so on.

XeonPony

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Re: Desulphation (Mad Science!) Experiments
« Reply #10 on: July 10, 2018, 09:52:53 AM »
Simpler method: Dump out electrolyte into tube, set aside, Wash with distilled water, dump into the set aside tub.

Refill battery with distilled water and put on a charge source, pump the voltage up to what ever is needed to sustain a steady 4amps, let charge and monitor Sp and temp, if temps get too high take off to cool, as Sp goes up add fresh water till it no longer goes up.

Take the electrolyte from the tub, filter it and boil it down, repeat till clean and concentrated, remix with distilled water till at proper charge level.

Sulfate is more soluble in water then it is in acid, and the washing will remove flaked off material so you'll end up with a clean desulfated battery.
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Harold in CR

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Re: Desulphation (Mad Science!) Experiments
« Reply #11 on: July 17, 2018, 09:11:07 AM »
xeon, after refilling battery with distilled water, is the battery reverse charged and discharged until ready to add cleaned electrolyte ?

XeonPony

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Re: Desulphation (Mad Science!) Experiments
« Reply #12 on: July 29, 2018, 02:52:04 PM »
it is simply washed clean, then add distilled water and charge at normal polarity while monitoring the sp, you should see it start to creep up over time, if it gets too high,  add fresh distilled water and keep it at the constant 4amp charge rate.

The 4amps is to reconvert the sulphate back into active material as it dissolves in the heated clean water.

Once the batteries Sp no longer moves up  it is time to add the now adjusted and clean electrolyte to the cells then run a charge discharge cycle to regenerate things further, then do a final capacity test
Ignorance is not bliss, You may not know there is a semie behind you but you'll still be a hood ornimant!

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thunderhead

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Re: Desulphation (Mad Science!) Experiments
« Reply #13 on: July 29, 2018, 03:07:09 PM »
I left a 55W bulb connected to them for about a week before attempting reverse charge.  At the end of that time the voltage shown on the terminals -- without load -- was millivolts.

For what it's worth the four batteries I did last summer overwintered quite well.  They seem to be performing like, well, normal batteries.

Great!

As I read it, what you did to your (85 Ah) rated batteries was:
  • Discharge to zilch at 5A or less over a week or more (including some extra time to insure things were really flat)
  • Reverse charge at 4A in 7 daily increments of about 40 Ah (presuming a 5 solar-hours rating for summer in Scotland), producing a slow (and reverse) forming charge of 280 Ah, about 3.3 times the rated capacity.
  • Discharged into a load and rechargedf (that panel again?  or something else?) a couple times to estimate capacity.
  • Discharge to zilch at 5A or less over a week or more (including some extra time to insure things were really flat)
  • Trickle charged them forward through a bulb (with an unspecified wattage), probably less than 4A and less than 5 hours per day.

It will be interesting to see whether/how that can be simplified and/or optimized.
  • Are the sleep periods in the reverse forming useful?
  • Can we take out the "test while reversed" cycles or do they do something useful (like break up bigger crystals)?
  • Can the forward charging and reforming go faster?
  • Do additional discharge-and-slow-recharge cycles in the forward direction help with the battery reforming?
and so on.

I think it would be interesting to do this "under laboratory conditions" to see what else can be learned.  Unfortunately I'm off-grid and I'm using a solar panel to provide the electricity -- and, in Ireland, solar supply is variable.

This year I'm doing another four batteries using an 80W solar panel that was previously being used for a fencer battery.  The discharge is through a 50W 12v bulb and the charge is directly from the panel.

So far the results are very similar: when flattened for a week it charges in reverse quite well, when again flattened for a week it charges up normal-direction but with more capacity than before.

I'm also about to go into hospital for eye problems (not brought on by sulphuric acid!) so I might monitor the process a bit less than previously.  But I'll let you all know how I get on.

joestue

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Re: Desulphation (Mad Science!) Experiments
« Reply #14 on: December 12, 2018, 01:16:50 AM »
I have tried this again with a new set of dead batteries.

These are B.B. batteries from a 48v UPS left in an unknown condition for unknown length of time. date codes are most likely aug 2006

The 8, 12v 5.5AH batteries were zero or less than 1 volt dc open circuit and rather high impedance, but absolutely no sign of expansion aka bulging.

They were  charged in parallel mostly in pairs, currents ranged from 0 to 3 amps each, 6-10cc's of water was added to each cell, which was enough to get the liquid above the fiberglass separator. 3 amps into a single battery would quickly overheat them and i'd estimate it took around 10 amp hours to get each 5AH battery to float at -13.8 at less than .3 amps current.
some of the batteries were open circuit for varying lengths of time, others quickly sucked up current, then quit, then started again. one out of the 8 is mostly totally open circuit and has been discarded unless i feel inspired to cut it open and inspect it internally.

currently the 7 are discharging in series and over the last 3 hours at .5 amps have decreased from -85.7 Open circuit, -83.7 under load  to -81 volts under load.

edit: ended the test at about 2 amp hours. final voltages under .473 amp load were 11.12,11.06,11.66,10.80,10.52,11.26,11.53.

85.7/7 is -12.24 average volts. a bit low. maybe a few cycles will improve the situation.


and that truck battery i mentioned in Sep 2017, i'm still using it. it got down to about 3 amp hours actual capacity. measured via a 100 watt 12v lighbulb it could power for all of hardly 10 minutes. i replaced it with 7, 5 ah batteries for about 3 months. i dumped out the acid from the truck battery and i still have said acid, about 3/4th gallon of 1.3SG. I filled the battery with water and put it on a float charger for 2 months. my brother needed the float charger so he took it at that point.

a month later, june of 2018 some of the 5 AH agm cells decided to melt and stick together, so i thought i would check on that truck battery. was presently surprised to find the acid was 1.2 SG and the voltage was 12.5.. even though it was open circuit for a month. said battery is a little weak, when the alternator isn't charging the voltage drops to maybe 11 volts under the load of the truck's headlights and heater fan, but it has enough capacity that i'm not concerned about it.. i'll probably get a few more years out of it.
« Last Edit: December 12, 2018, 02:29:40 AM by joestue »
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ruddycrazy

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Re: Desulphation (Mad Science!) Experiments
« Reply #15 on: December 12, 2018, 06:11:27 AM »
I found with N70 batteries they last about 5 years on my tractor then they won't start it again even after being left on a charger for a week.

So decided to try the alkaline trick on one, drained all the acid out of the battery and gave it flush out with rainwater. The flush was kept and is now great for re-sharpening old files. Then using baking soda started to neutralize the acid, did 3 batchs until no bubbles could be seen and did a 4th just to be sure.

Went to the local hardware and bought some pool folluclent (magnesium sulphate) and made a saturated solution in rainwater to top all the cells up.

Then left it on 2 off 5 watt solar panels for a month until I saw 16 volts then back into the tractor it went. The tractor started first kick so now on the roof of the tractor sits those 5 watt solar panels and the battery is still going after 3 years starting my fiat 45hp tractor with no problems.

joestue

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Re: Desulphation (Mad Science!) Experiments
« Reply #16 on: December 13, 2018, 10:11:15 PM »
discharged 7 in parallel last night, due to confusion terminated the test long before full discharge. pulled 8 amp hours out, then put 9.5 back in.

discharged the 7 in parallel today, 4.5 hours at 4.6 amps average, ending at 10.80 volts under load. 11.1 volts open circuit after discharge. about 21 amp hours removed. currently charging.

so after a single reverse polarity charge, and 2 charge and discharge cycles at about half capacity, the batteries are at 55% nameplate amp hours.

My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

joestue

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Re: Desulphation (Mad Science!) Experiments
« Reply #17 on: December 31, 2018, 02:53:24 AM »
discharged and charged them again in series, removed the weakest battery which appears to have a cell that went partially open circuit.

the remaining 6 batteries were charged and then discharged in parallel: terminated the test after 15 amp hours removed in just over 3 hours. ending voltage at 11.54V under 4.8A load.


--much more testing will have to be done to determine if reversing the polarity is an effective stop gap measure. i think it is. but by the time the battery is at 50% amp hours its likely major plate damage has already been done and reversing the polarity may not be able to stop or reverse it.
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

Bossrox

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Re: Desulphation (Mad Science!) Experiments
« Reply #18 on: March 09, 2024, 05:03:50 PM »
Thx for this post, I've got 3 big batts with bad cells so I'm gonna give this a whirl to see what happens. You might of saved me some serious bux!