Should I desulphate the battery first? Or charge the battery first? Very low state of charge, barely able to start the car.
Desulfate or charge first?
- Thread starter meadows
- Start date
How old of battery are we talking about? I tried to do the desulphate the battery thing with different smart chargers and different batteries have not find it to do much if anything. I almost to the point of thinking it is a gimmick. I would just give it a good long charge see how it goes.
Older batteries with the caps removed so I can see the plates. I have charged them at a low rate of about 0.5 amps for several days. I could see that every second plate turned dark as the sulfate crystals disappeared.
The BatteryMinder does not have any option to turn on or off desulfating. It does its own thing according to the needs of the battery. I just put my 3 boat batteries on BatteryMinder chargers for the winter. The two flooded batteries turned on the "battery low" light. And they are also desulfating as soon as they were connected to the charger.
My battery charger does the desulphating and the charging separately.
That is why I’m asking which one to do first
That is why I’m asking which one to do first
I would charge and then desulfate.
How long is the desulfate cycle?
Be sure to check the cells for battery acid level before doing anything
And if the battery is dead and frozen, let it thaw for a day or two first
I think the cycle lasts for 24 hours for desulfation
I doubt if you will get much desulfation in 24 hours.
The whole idea of desulfation seems between a theory and a guessing game. It probably works for batteries in a certain condition and does little for a battery not in that certain condition. Your trying to dissolve sulfur crystals back into solution. And difficult or impossible to see exactly what's going on in each cell.
BatteryMinder says it can take a week or weeks to desulfate a battery.
You’d have to keep the battery on the charger for a good long while for any positive results I believe. I had what I thought was a cooked battery in my boat. It took all winter, but I was able to bring it back to good health. A month into my experiment not much had changed, another 3 months and it was good. The best way to desulfate imo, is to start with new and try and keep it that way. Unless you’ve got a long time.
Having built 2 desulfators by hand, when it goes well it takes weeks, or months. The voltages for effective desulfation, I would not want to expose vehicle electronics to. A kickback desulfator can see very short, but very high spikes such as 60V if the battery is stubborn and unable to absorb the energy.
I’ve had better short term results using an adjustable power supply pushing limited current over-voltage into flooded batteries.
I’ve had better short term results using an adjustable power supply pushing limited current over-voltage into flooded batteries.
f355spider
$50 Site Donor 2026
How long desulfation takes completely depends on the algorithm the battery charger or tender uses. Some do continous desulfation, like Battery Minder and Battery Saver brands. Those can take a long time, as it does the desulfation during the float stage.
Others have an automatic desufation mode that is only triggerred when the battery tender or charger detect specific parameters it is looking for. Those can take as short as a few hours to a day. And the third way sounds like the OPs charger which has a specific setting you can activate at the operators will, when ever they feel like attempting desulfation. Again, those also can take a few hours to a day.
I never saw any benefit from the various desulphation gizmos I've tried on old batteries. Like Meep mentioned above, the best results I've seen were from doing an equalization charge (basically over charging the battery at 16.2V with the electrolyte bubbling for a couple of hours) using an adjustable power supply, followed by a longer period at a bit lower voltage and with the current turned away down so the electrolyte isn't visibly bubbling. You might need to add some water after doing this.
Basically these frequency-based desulfators “vibrate” the battery by sending a high potential pulse to the battery in an attempt to “break through” and weaken the sulfate and coax it back into solution. It’s like a ringing a bell - ping it and it will ring, without pressing a constant high potential charge that would risk breaking it off where it physically destroys the battery.
The ones I made were basically a buck circuit through a choke at 1 kHz. The gentler of the two was designed to be used parallel with a charger. If the battery was healthy, the very short pulses looked like 16v on an oscilloscope. But if the battery was tired, the pulses showed as over 50v with electrical “back pressure.” This unit did work - I picked up a bunch of 12V 7A batteries from the dump and tested it to measure effectiveness. It took 6-12 weeks 24/7 to get the full extent out of it. It would not bring it back to 100% capacity.
Those high spikes kill electronics over time, even as short as they were. I had to modify the chargers to keep from harming them.
I built a second with about 2.5x the output power. It was not any more effective, which was interesting to me.
Having done measured tests, I can’t imagine these storebought systems would be even fractionally effective, since they don’t want to risk damaging the vehicle it’s attached to. There are other ways to promote the desulphation activity and I’ve not tested them myself, so I won’t discount them, but the battery is at the end of the day a high school chemistry experiment, and some reactions take time.
I recall during the day witnessing the battery bank for a good old POTS (plain old telephone system) station. Hundreds of cells, each the size of a 5 gallon glass bucket, with an open lid. It’s been a while. IIRC, desulfation was done periodically by hand, where they’d pull the plates out of them and scrape them off by hand. Wouldn’t want that job.”leclanche” cells?
The ones I made were basically a buck circuit through a choke at 1 kHz. The gentler of the two was designed to be used parallel with a charger. If the battery was healthy, the very short pulses looked like 16v on an oscilloscope. But if the battery was tired, the pulses showed as over 50v with electrical “back pressure.” This unit did work - I picked up a bunch of 12V 7A batteries from the dump and tested it to measure effectiveness. It took 6-12 weeks 24/7 to get the full extent out of it. It would not bring it back to 100% capacity.
Those high spikes kill electronics over time, even as short as they were. I had to modify the chargers to keep from harming them.
I built a second with about 2.5x the output power. It was not any more effective, which was interesting to me.
Having done measured tests, I can’t imagine these storebought systems would be even fractionally effective, since they don’t want to risk damaging the vehicle it’s attached to. There are other ways to promote the desulphation activity and I’ve not tested them myself, so I won’t discount them, but the battery is at the end of the day a high school chemistry experiment, and some reactions take time.
I recall during the day witnessing the battery bank for a good old POTS (plain old telephone system) station. Hundreds of cells, each the size of a 5 gallon glass bucket, with an open lid. It’s been a while. IIRC, desulfation was done periodically by hand, where they’d pull the plates out of them and scrape them off by hand. Wouldn’t want that job.”leclanche” cells?
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f355spider
$50 Site Donor 2026
I've had great results with what I suspect was sulfation on a flooded and an AGM, using a Battery Minder battery charger. In both cases, it took several weeks of plugging in each evening when parked. I put pig tail connectors on each car so it was easy to connect without having to open the hood or anything. The AGM came back about 100CCA on my tester and the flooded about 70CCA. I kept seeing improvement each week until about 6 or 7 weeks out.
Both were getting connected to a battery tender without any desulfation mode regularly prior, so I know the improvement was not from simply using a battery tender.
I've also used a Granite Digital "Battery Saver" that has continuous automatic desulfation during float, and it did not help the AGM at all. That was when I got interested in purchasing the Battery Minder to try.
That’s a good data point!
f355spider
$50 Site Donor 2026
Battery Minder even warns in their instructions that the process is slow and will take weeks to see the results.
I still connect both cars once or twice a week for overnight charging/maintenance. I have a couple other "garage queens" that remain connected continuously.
I've heard of chargers with faster desulfation processes of less than a day, but require the battery to be disconnected from the car to prevent damaging electronics.
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My boat batteries are on BatteryMinder chargers until April. (In my garage). So they will get months of the desulfation function. No idea if the batteries were sulfated or not. They go weeks or a month between use on the boat.
Factory battery in my '13 Ski Doo, Yuasa YTX20L-BS AGM, still testing good. Been on a Battery Minder since it came home.
I've got 9 BM's in play on all my batteries that are parked or stored. The BM's have more than paid for themselves.
I've got 9 BM's in play on all my batteries that are parked or stored. The BM's have more than paid for themselves.
