I have it hooked up with two 150ohm resistors in parallel to a 12v battery to give it enough voltage to start pushing a charge into it.
at first it was only drawing like 1 or 2 mA of current and the voltage across it was close to 12v
after 15 minutes it quickly started dropping down to 11.5v and then 30 minutes later it dropped quicker down to 10v and an hour or so later it's now at 7.5v and still dropping but its dropping slower now. and its holding voltage better too
when i first got it it was at like 2.5v at resting voltage now its holding closer to 5v at rest and drawing close to 100mA of current. and the voltage is still dropping slowly as it maybe gets more charge?
can it be saved? it came out of a kids powerwheels car thing
at first it was only drawing like 1 or 2 mA of current and the voltage across it was close to 12v
after 15 minutes it quickly started dropping down to 11.5v and then 30 minutes later it dropped quicker down to 10v and an hour or so later it's now at 7.5v and still dropping but its dropping slower now. and its holding voltage better too
when i first got it it was at like 2.5v at resting voltage now its holding closer to 5v at rest and drawing close to 100mA of current. and the voltage is still dropping slowly as it maybe gets more charge?
can it be saved? it came out of a kids powerwheels car thing
When a battery of this type is left discharged it can suffer from sulphation of the plates and that may not be recoverable.
The official Yuasa guidelines are to charge at higher voltage and with the current limited to one tenth the battery's capacity. That voltage could be as high as 16 to 20 volts but the current in your case must not exceed 0.5 amps. There is also a time limit of 12 hours.
The battery should also not be left unattended whilst doing this.
The official Yuasa guidelines are to charge at higher voltage and with the current limited to one tenth the battery's capacity. That voltage could be as high as 16 to 20 volts but the current in your case must not exceed 0.5 amps. There is also a time limit of 12 hours.
The battery should also not be left unattended whilst doing this.
If the battery is sulfated, there exists in the web a thing called "desulfator", a guy I know tried it in a battery from a car and he affirms that it works. I'm skeptic about it, but as it is easy to build, perhaps you can try it.
desulfator circuit - Google Search
desulfator circuit - Google Search
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i cant increase it that much. i'd need more than 12v and i dont want it to build up a lot of gasses or boil the battery.
right now its at about 6.9v and still slowly dropping in voltage but the current is still slowly increasing. i'm going to leave it on for a while before i try to charge it at more current. its still not charged enough to charge it normally. need to get the internal resistance low enough that it can take a normal charge current.
right now its at about 6.9v and still slowly dropping in voltage but the current is still slowly increasing. i'm going to leave it on for a while before i try to charge it at more current. its still not charged enough to charge it normally. need to get the internal resistance low enough that it can take a normal charge current.
ok the resting voltage is just about 5.4v i hooked it up to my normal battery charger set to 3 cells 6v pb/lead acid mode and current set to 100mA and its almost to the point where it can take a normal charge. the voltage went up to 7.35v but its internal resistance is decreasing further. its dropped down to 7.2v after a minute or two of being on charge.
some time charging later the voltage dropped to 6.8v on charge. and resting voltage is 5.5v!
edit: an hour later its drawing a full 200mA! I upped the current from 100mA to 200mA and its above 5.6v resting voltage and on a charge its about 7v now. the internal resistance is going down even more and the resting voltage and the voltage when on charge are getting closer. with higher current too.
edit: an hour later its drawing a full 200mA! I upped the current from 100mA to 200mA and its above 5.6v resting voltage and on a charge its about 7v now. the internal resistance is going down even more and the resting voltage and the voltage when on charge are getting closer. with higher current too.
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cant edit my other reply so new reply. i increased the current again to 300mA and the voltage went to about 7.1v and after 15 minutes or so it went down to 6.8v and its still slowly decreasing more. but its going slower and slower i think its starting to take an actual charge now and desulfating the battery at the same time thats why the current is increasing while at the same time the resting voltage is also increasing slowly! i think its desulfating all on its own. it was super super flat when i first got it.
edit again:
I also want to know if the voltage starts increasing again above 7v after a while of being on charge and the current starts decreasing does that mean its getting close to full on charge?
how long will it maybe take until the voltage starts to increase again instead of decreasing? its at about 6.7v now
I increased the current up to 500mA now and the voltage went up to about 7.2v then 30 seconds later decreased again down to 7.1v and slowly decreasing again. its staying cold the whole time i felt it and its not even slightly warm. feels cool like room temperature.
edit again:
I also want to know if the voltage starts increasing again above 7v after a while of being on charge and the current starts decreasing does that mean its getting close to full on charge?
how long will it maybe take until the voltage starts to increase again instead of decreasing? its at about 6.7v now
I increased the current up to 500mA now and the voltage went up to about 7.2v then 30 seconds later decreased again down to 7.1v and slowly decreasing again. its staying cold the whole time i felt it and its not even slightly warm. feels cool like room temperature.
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I have done them in the past.
I just charged them with a high voltage of about 30 volts limited with a resistor to set the short circuit current below 100ma.
I dabbed a car head light bulb across it each time I checked it and this brought the charge current up showing that it was recovering.
The one I was fixing was down to 0.2 volts.
I just charged them with a high voltage of about 30 volts limited with a resistor to set the short circuit current below 100ma.
I dabbed a car head light bulb across it each time I checked it and this brought the charge current up showing that it was recovering.
The one I was fixing was down to 0.2 volts.
wow thats really low! 0.2v! dang!
Mine was only at 2.5v-ish when i first got it.
it took about an hour to go from charging at 1mA of current to about 20mA. then about 30 minutes to go from 20mA to 100mA
and 2 or 3 hours later its charging at a full amp and not getting even a little bit warm and its resting voltage is now well over 6v holding a good charge and can even light up a 6v 0.5A lamp!
I'm going to charge it until its completely full it might take all day though considering how dead it was.
Edit again:
The voltage has switched direction while charging and it is now RISING back up very slowly!!
Celebration!!! Free 6v battery!
Mine was only at 2.5v-ish when i first got it.
it took about an hour to go from charging at 1mA of current to about 20mA. then about 30 minutes to go from 20mA to 100mA
and 2 or 3 hours later its charging at a full amp and not getting even a little bit warm and its resting voltage is now well over 6v holding a good charge and can even light up a 6v 0.5A lamp!
I'm going to charge it until its completely full it might take all day though considering how dead it was.
Edit again:
The voltage has switched direction while charging and it is now RISING back up very slowly!!
Celebration!!! Free 6v battery!
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The resting voltage (at least 12 hours after taking it off charge) should be around 6.35 volts at a guess. Remember you need to put a lot of energy back into the battery to bring it back to a reasonable charge.
If its a 5Ah battery then you need to put at least that amount back into it. So if its charging at 1A then it needs around 5 hours of that. Its normal for the current to fall off as the voltage rises.
When fully charged it should only be drawing a a few tens of milliamps with anything up to 7 volts applied across it.
If its a 5Ah battery then you need to put at least that amount back into it. So if its charging at 1A then it needs around 5 hours of that. Its normal for the current to fall off as the voltage rises.
When fully charged it should only be drawing a a few tens of milliamps with anything up to 7 volts applied across it.
i know. and im just excited its starting to charge normally now like a good SLA/AGM battery in good condition. its no longer dropping in voltage and increasing in current anymore.
the current is staying about the same now and the voltage is going in the other direction. up very slowly. its was around 6.73v when the voltage stopped dropping and has now increased up to 6.8v
I have been able to increase the charge current up to the batteries rated maximum "initial current" of 1.5 amps and its charging good now
the current is staying about the same now and the voltage is going in the other direction. up very slowly. its was around 6.73v when the voltage stopped dropping and has now increased up to 6.8v
I have been able to increase the charge current up to the batteries rated maximum "initial current" of 1.5 amps and its charging good now
that's good.Remember to stay safe with these kind of batteries. The current available can be many many tens of amps and that can do serious damage if accidentally shorted. Be very careful if you wear any metal watch bracelets and that kind of thing as the current could be enough to melt the metal if you accidentally shorted the terminals while moving it around.
just about 1.5AH has been charged into the battery so far. (approximately since i dont remember exactly how much has been put in since i stopped and adjusted the charger a few times.) its showing about 639mAh right now
and i remember it had at least 400-something and 200-something previous adjustments and i know i charged it for maybe 50 to 100mAh again before. something like that.
seems to be charging just fine. not getting warm. holding a good strong voltage above 6v too when the charger is taken off.
and i remember it had at least 400-something and 200-something previous adjustments and i know i charged it for maybe 50 to 100mAh again before. something like that.
seems to be charging just fine. not getting warm. holding a good strong voltage above 6v too when the charger is taken off.
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