Is it possible to resurrect a lead acid battery from the dead?
I have an old 12 volt automobile battery that was stored for sometime in a discharged state. The battery voltage read around
6 volts in the discharged state. I charged it at 1 amp for 10 hours and then tested the capacity using a automotive tail light drawing 1.3 amps. The battery voltage fell from 12.5 volts to around 9 volts within
1.5 hours indicating the capacity was not too much.
When I again recharged the battery, it sustained the load for a longer period indicating the capacity had increased to around 5 amp hours.
I'm wondering if cycling the battery over several charge and discharge cycles will improve the capacity?
This charge and discharge cycling seems to improve the capacity for a couple cycles, how much improvement should I expect from several charge and discharge dycles?
You need to deep cycle it according to what I have been told. Fully charge it with a good charger (5 or 10 amps) then run it down with a headlamp load to dim then repeat. A good battery shop could tell you how to do it.
Rubbish. Car batteries are not designed for deep discharge cycling (running them completely flat). They have no need to be. Doing so will damage a good one.
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If you use a charger that has "desulfator" capability, you can reverse much of the sulfation that has taken place on the plates. I have heard many claims on this , both for informed and un-informed sources. Lots of patents have been issued for desulfators. Lots of lab tests..... It probably works.
The desulfator chargers cost a little more, tho. Instead of putting a DC or pulsating unipolar AC on the plates, they put a high frequency pulse on the plates to charge the battery with thousands of little pulses per second, the theory being that it "shakes loose" the sulfation. Not complicated, but it takes more than a transformer and a rectifier in the charger......
I haven't tried it myself, but have researched it pretty well. I think it probably works......
The fact that it got to 12.5V indicates that it is probably not shorted internally. Charge it up again and leave it overnight. If it still measures above 12V then it is likely to be restorable.
Open up the cell caps and look down each one with a flashlight. You should see the plates with paper separators between them. The paper will be tan colored and I'm guessing that you'll see grey plates between each tan separator. If so, your best bet is to charge the battery extremely slowly.
I recommend that you just put a small lamp between the charger and the battery, in series, to limit the current. A charging current of about
50 mA is about right. You will need to keep this up until half of the plates turn chocolate brown. At that point, the battery will be fully charged. If your battery is badly sulfated, this process may take more than a week.
During that time you should check the voltage across the battery. You can do this at the same time that you're charging it slowly. If the battery voltage every falls below 12V during this time, you have a shorted cell, and the battery is probably not salvagable.
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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
No. The only way to store a *good* battery is to fully charge it then drain the acid and rinse out with suitable soft water. Seal it in shrink wrap and it will keep for many years, to be revived with fresh electrolyte and a re-charge.
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Yes, it will seem agonizingly slow, but it needs to be slow because the lead sulfate can only be converted to lead as quickly as it will go into solution, and the lead sulfate in a sulfated cell is much less soluble than that in a freshly discharged cell (different crystal structure.)
If you try to force the charging process, you'll just hydrolize water, and this can damage the sintered plates if it happens too vigorously.
You don't want to "drive off" the lead sulfate, as that takes sulfate ions out of circulation and just leads to buildup at the bottom of the cell which will eventually short it out.
With patience, this will generally work if the only problem is sulfation, which is what happens to a battery that is left in a discharged state for a long time. The lead sulfate slowly converts to a much less soluble crystal structure over time.
I've done this many times, but it doesn't always work. About half the time you'll find that one or more of the cells are shorted and the battery is only useful as a tradein.
I have never managed to restore a shorted cell.
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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
I have found from experience that if you keep a lead acid battery fully charged using a trickle charger, and make sure the water is kept full as well that it will keep for many , many years.
I miss the days when you could buy a battery that was serviceable. A heavy glass plate case with bolt on top and removable plates. They would last forever as long as one was willing to do a bit of service work.
In sci.electronics.repair on 21 May 2005 20:14:08 -0700 snipped-for-privacy@att.net posted:
Make sure you have adequate water in each cell, and use steam distilled water. It's for sale at the supermarket in gallon bottles. Also useful in steam irons. (although my plastic bottle started leaking after 5 or 10 years.) The cell is full when the water level is high enough that it reaches the bottom of the circular tube through which one fills the battery. One can see that this is the case when he sees the miniscus in a circle around the bottom of the tube. When the level is lower, there is a miniscus, but it is along the edges of the much larger rectangle that is the cross section of a cell *below* the filler tube. In other words, when you can see the miniscus, the battery cell is sufficiently full. Don't fill much more than that.
Though there are some sealed autobatteries I think, most of them now are designed to look like they are sealed. That is, they don't have the 6 soda-pop-bottle top caps that batteries used to have, one for each cell. Instead there are 2 flat panels that pry off, each with three caps molded to the bottom. I think there is usually a 2 or 3 inch, narrow slot somewhere along the edge that indicates the cap comes off, and is a good place to pry, but I'm not sure how obvious it is in all models.
i HAVEN'T paid too much attention lately, but when I did, everything I ever heard was that one had to charge a lead acid battery slowly to get the best result.
If one charges too fast, the lead in solution gets deposited back on the lead plate before the lead sulfate** can dissolve. The result is what is called spongey lead. I guess one problem that results from this is that the sulfate radicals are no longer dissolved and therefore there is not as much H2SO4.
So a one amp charger is very good. And slower would be better I guess, but one would have to do something additional to make it slower. When I ran my battery down to the ground, unintentionally but for reasons I forget right now (leaving the lights on?) it would take about 24 hours to recharge it with a one amp charger. (I guess at 50 milliamps it would take about 20 days, n'est pas?)
When I got a jump and had to go somewhere and was therefore going to recharge the battery while driving, I kept the heater fan on high and the headlights on to slow the charging rate, but I probably didn't slow it enough.
Charging the battery tends to emit hydrogen through the vents, which is why people are warned against sparks and to have adequate ventilation, and I already mentioned the loss of sulfate radicals, the other half of sulfuric acid. Yet, I've also read not to add more acid, since by the theory that goes with that, only water is lost from the battery. The two seem to contradict each other.
**PbSO4, I think it is, but maybe it was lead oxide (PbO2),
What makes lead acid batteries rechargeable is that the products of electrical generation remain either in solution or soluable. In, for example, carbon zinc flashlight batteries, this is not the case.
However, not all gets redissolved, and there is an empty inch or two at the bottom of batteries where chunks of lead compounds, or detached lead can settle. For this purpose, the more empty space the better, because I think the most common cause of cell shorting is that the level of junk in the bottom gets high enough to touch two consecutive plates, or two other plates that should not be connected, except through the acid solution. OTOH, the more empty space at the bottom, either the bigger the battery and the more acid needed, or the smaller the plates and the lower the maximum output per time.
Meirman
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In sci.electronics.repair on Mon, 23 May 2005 23:00:20 -0500 "Bob Shuman" posted:
I guess this is OT, but I like this story. In 1966 I had a '50 Olds with a 6-volt battery, not strong enough unless totally charged to start my big V-8 in the cold Chicago winter (which is why they started using 12 volt) I had a 1 amp 6volt/12volt charger, given to me by my cousin who gave me the car.
I put the charger inside the hood and plugged into an extension cord whenever I was home, but 6 volts was not enough, and I then set it to
12 volts. And the car started all winter. Inside the charger, the glass circuit breaker (which looked like a long glass neon light or a small xmas tree light) tripped ever 30 seconds and reset automatically
5 seconds later, and it ran like that day and night for 4 months. I guess that is about 300,000 times. Years later I had to replace the selenium rectifier with regular diodes, but now it is almost 40 years later and the charger still works fine, including its circuit breaker.
The extension cord was something I made up from heavy twisted-pair wire, with steel strands it seemed, rather than copper. It plugged into the pantry of the place we lived and two of the four months, although suspended at both ends, the wire was under the snow for 15 feet, but that didn't cause any problem either. Not even a blown fuse inside where the house.
Meirman
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Indeed, but few will bother. A decent recharge every few months or so would do as well. But I've a suspicion the makers incorporate separators that self destruct if left in the acid.
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