I've just started with my first desulfater and thought I'd write about my experiences before and during its use, and maybe ask a few questions. First,
the background:
About this time last year, I had to put my wheelchair into storage rather abruptly. The batteries had a partial charge, probably between 20 and 40%. I retrieved it a couple of weeks ago, only to find that the batteries were nearly dead. These are AGM type, but they have pressure-release filler caps. 12v, 33AH. We called the wheelchair manufacturer, who told us that the batteries had "solidified". They offered to sell and install a new pair for $140.
One was reading about 6 volts when I checked it, the other about 7.5 volts. Neither one was able to absorb much of a charge, drawing less than 10 mA from a 12v 1A power supply I had on hand. The wheelchair's own automatic charging system didn't even know the batteries were there and refused to switch on at first. I took them out to my car and tried to give them a boost, but that didn't do any good. So, frustrated, I put them in the trunk with the intent that I'd eventually just recycle/replace them. They remained there in the cold for a few days, but the temperature never got below about 40, thankfully.
I changed my mind about replacing them and ordered parts for a desulfater based on what I've read here on the forums and on the main site. In the meantime, I brought the batteries back in the house and checked the voltage again just out of curiosity. They were down to less than 3 volts each, probably due to the cold. After they came back up to room temperature, they were back in the 6 to 8 volt range.
When I looked through the fill holes, the plates were clearly visible, covered with a thick white goop that resembled toothpaste. They were bone dry (far dryer than an AGM should be), so I added some water, which they were happy to absorb, until all six cells were covered. From what I've read, you're not supposed to be able to do this with AGM's, much less NEED to, but I digress...
I put them on the 12v power supply and, after several hours, they came back to life, slightly. The wheelchair charger now recognizes their presence and is able to charge them to about 15% capacity. In fact, they get rather warm under charge, almost downright hot. They overcharged at least once, losing some of their electrolyte (not much, maybe a teaspoon or two tops). I decided not to do any further charging with the wheelchair's charger, for fear of damaging them. One thing I noticed is that the liquid that escaped from the batteries was brown. I accidentally got a taste of it when I reached to scratch my lip, not realizing I'd picked up a trace of it on my hand..... tastes like really strong vitamin C.
Both of the battery cases are slightly bulged now from the overcharging, but it doesn't look serious. I've seen far worse on batteries that still worked fine.
Anyway, I topped the water off again, (so far, that makes for a total of about a quart between the two batteries) and tested them on the 12v power supply. They were able to draw about 1 amp while reading 11.05 volts. Off the power supply, they hold at around 11.00 volts without any load, at least for a couple of hours, and when loaded, they can source more than 10 amps (the limit of my meter). I'm not sure what the voltage is under such a heavy load.
When I hook them up to the wheelchair, I can move around at the chair's maximum speed, with the usual amount of acceleration that I should get at that speed, and I can use it normally for at least a few hours of light duty operation in my house, so it seems like the batteries can source a decent amount of power for at least a while.
I now have a desulfater running (Ron's N-channel circuit, dialed back to 2.7% duty cycle). As of this writing, it has been going for about 48 hours straight. About half of that time, I've had the 12v power supply attached, just to keep the batteries from going flat. Both batts are now slightly warm to the touch, no more than a few degrees above ambient temperature. The 12v power supply, however, has been working its poor little heart out and is pretty warm :-)
I have not been able to get them above 11.31 volts so far, but it has only been a couple of days.
At one point, they were drawing about 800 mA while reading 11.31 volts. The amps being drawn seems to vary significantly, and I can't see any pattern in the voltage. Right now, they're drawing about 1.15 Amps (!) while reading 11.15 volts. This power supply delivers about 16 volts without any load.
When I switch my meter over to the 200VAC range, I pick up about 23.8 volts AC as long as the probes are on the right terminals. Reverse the polarity and the meter reads 0 volts AC. This is down from a reading of about 24.5 volts AC yesterday. I've read elsewhere here that the lower the peak voltage, the better the batteries are doing (the less sulfation they have).
I don't know all that much about lead-acid batteries, and after reading some sources mentioned here on the forums, I am left with several questions as they pertain to desulfating.
1. Do any of my readings so far make sense?
2. Does this AC voltage reading correlate with the actual peaks the desulfater is putting out? Without my scope (which is still in storage), I'm left with just this little voltmeter. Do I still need to throw together a peak detector?
3. Is the 800 mA to 1.15 A that the batteries are drawing normal at this point?
4. Did I do damage to the batteries when they got overcharged the other day? Is it permanent? Why did my wheelchair's supposedly automatic charger system do this in the first place?
5. If these are truely AGM batts, why do they have removable fill caps? Why does the label also declare them to be VRLA's? Why did they wake up when I added water? Were they just built in a parallel universe?
6. While this desulfater is running, I've left all the fill caps loose (to prevent any sudden pressure releases or spraying). Despite the lack of pressure that should force hydrogen/oxygen recombination, the batteries have not used a significant amount of water since that second top-off. Should I drain the excess at this point?
7. At some point, a tiny piece of that thick white goop somehow made it out of the battery. This piece of white material had about the consistency of clay. Is this indeed a piece of lead sulfate?
8. Since I started working on these batteries, small cracks have developed in the white goo, clearly along the edges of the plates. Is this a good sign?
9. If the batteries' power draw from the 12v power supply is increasing, I assume the batteries' internal resistance is dropping. Is this a good sign?
10. Since 1A is about as much as a battery should take during this, and that's about all my little power supply is technically rated for, how would I limit the current draw without affecting the desulfater? A household light bulb perhaps?
11. I also have a spare PC power supply on hand that's capable of delivering some 5A at 12v. Will this be of any use in this project?
12. AGM batteries are supposed to be able to handle a couple of years between charges. These batts were only a couple of years old and very healthy before they went into storage. Why did they take such a performance impact while in storage for about a year? Did my leaving them connected to the chair while in storage cause this?
13. Given the history and weird construction, should I expect a shorter or longer recovery period than predicted by the one-day-per-pound rule?
14. Only a very small amount of bubbles can be seen in each cell, clinging to various surfaces similar to the carbonation bubbles that cling to the inside of a soda bottle. Is this normal? Should there be a great deal of bubbling, or none at all, or... ?
Thanks in advance.
About this time last year, I had to put my wheelchair into storage rather abruptly. The batteries had a partial charge, probably between 20 and 40%. I retrieved it a couple of weeks ago, only to find that the batteries were nearly dead. These are AGM type, but they have pressure-release filler caps. 12v, 33AH. We called the wheelchair manufacturer, who told us that the batteries had "solidified". They offered to sell and install a new pair for $140.
One was reading about 6 volts when I checked it, the other about 7.5 volts. Neither one was able to absorb much of a charge, drawing less than 10 mA from a 12v 1A power supply I had on hand. The wheelchair's own automatic charging system didn't even know the batteries were there and refused to switch on at first. I took them out to my car and tried to give them a boost, but that didn't do any good. So, frustrated, I put them in the trunk with the intent that I'd eventually just recycle/replace them. They remained there in the cold for a few days, but the temperature never got below about 40, thankfully.
I changed my mind about replacing them and ordered parts for a desulfater based on what I've read here on the forums and on the main site. In the meantime, I brought the batteries back in the house and checked the voltage again just out of curiosity. They were down to less than 3 volts each, probably due to the cold. After they came back up to room temperature, they were back in the 6 to 8 volt range.
When I looked through the fill holes, the plates were clearly visible, covered with a thick white goop that resembled toothpaste. They were bone dry (far dryer than an AGM should be), so I added some water, which they were happy to absorb, until all six cells were covered. From what I've read, you're not supposed to be able to do this with AGM's, much less NEED to, but I digress...
I put them on the 12v power supply and, after several hours, they came back to life, slightly. The wheelchair charger now recognizes their presence and is able to charge them to about 15% capacity. In fact, they get rather warm under charge, almost downright hot. They overcharged at least once, losing some of their electrolyte (not much, maybe a teaspoon or two tops). I decided not to do any further charging with the wheelchair's charger, for fear of damaging them. One thing I noticed is that the liquid that escaped from the batteries was brown. I accidentally got a taste of it when I reached to scratch my lip, not realizing I'd picked up a trace of it on my hand..... tastes like really strong vitamin C.
Both of the battery cases are slightly bulged now from the overcharging, but it doesn't look serious. I've seen far worse on batteries that still worked fine.
Anyway, I topped the water off again, (so far, that makes for a total of about a quart between the two batteries) and tested them on the 12v power supply. They were able to draw about 1 amp while reading 11.05 volts. Off the power supply, they hold at around 11.00 volts without any load, at least for a couple of hours, and when loaded, they can source more than 10 amps (the limit of my meter). I'm not sure what the voltage is under such a heavy load.
When I hook them up to the wheelchair, I can move around at the chair's maximum speed, with the usual amount of acceleration that I should get at that speed, and I can use it normally for at least a few hours of light duty operation in my house, so it seems like the batteries can source a decent amount of power for at least a while.
I now have a desulfater running (Ron's N-channel circuit, dialed back to 2.7% duty cycle). As of this writing, it has been going for about 48 hours straight. About half of that time, I've had the 12v power supply attached, just to keep the batteries from going flat. Both batts are now slightly warm to the touch, no more than a few degrees above ambient temperature. The 12v power supply, however, has been working its poor little heart out and is pretty warm :-)
I have not been able to get them above 11.31 volts so far, but it has only been a couple of days.
At one point, they were drawing about 800 mA while reading 11.31 volts. The amps being drawn seems to vary significantly, and I can't see any pattern in the voltage. Right now, they're drawing about 1.15 Amps (!) while reading 11.15 volts. This power supply delivers about 16 volts without any load.
When I switch my meter over to the 200VAC range, I pick up about 23.8 volts AC as long as the probes are on the right terminals. Reverse the polarity and the meter reads 0 volts AC. This is down from a reading of about 24.5 volts AC yesterday. I've read elsewhere here that the lower the peak voltage, the better the batteries are doing (the less sulfation they have).
I don't know all that much about lead-acid batteries, and after reading some sources mentioned here on the forums, I am left with several questions as they pertain to desulfating.
1. Do any of my readings so far make sense?
2. Does this AC voltage reading correlate with the actual peaks the desulfater is putting out? Without my scope (which is still in storage), I'm left with just this little voltmeter. Do I still need to throw together a peak detector?
3. Is the 800 mA to 1.15 A that the batteries are drawing normal at this point?
4. Did I do damage to the batteries when they got overcharged the other day? Is it permanent? Why did my wheelchair's supposedly automatic charger system do this in the first place?
5. If these are truely AGM batts, why do they have removable fill caps? Why does the label also declare them to be VRLA's? Why did they wake up when I added water? Were they just built in a parallel universe?
6. While this desulfater is running, I've left all the fill caps loose (to prevent any sudden pressure releases or spraying). Despite the lack of pressure that should force hydrogen/oxygen recombination, the batteries have not used a significant amount of water since that second top-off. Should I drain the excess at this point?
7. At some point, a tiny piece of that thick white goop somehow made it out of the battery. This piece of white material had about the consistency of clay. Is this indeed a piece of lead sulfate?
8. Since I started working on these batteries, small cracks have developed in the white goo, clearly along the edges of the plates. Is this a good sign?
9. If the batteries' power draw from the 12v power supply is increasing, I assume the batteries' internal resistance is dropping. Is this a good sign?
10. Since 1A is about as much as a battery should take during this, and that's about all my little power supply is technically rated for, how would I limit the current draw without affecting the desulfater? A household light bulb perhaps?
11. I also have a spare PC power supply on hand that's capable of delivering some 5A at 12v. Will this be of any use in this project?
12. AGM batteries are supposed to be able to handle a couple of years between charges. These batts were only a couple of years old and very healthy before they went into storage. Why did they take such a performance impact while in storage for about a year? Did my leaving them connected to the chair while in storage cause this?
13. Given the history and weird construction, should I expect a shorter or longer recovery period than predicted by the one-day-per-pound rule?
14. Only a very small amount of bubbles can be seen in each cell, clinging to various surfaces similar to the carbonation bubbles that cling to the inside of a soda bottle. Is this normal? Should there be a great deal of bubbling, or none at all, or... ?
Thanks in advance.
