Reverse charging experient
- Thread starter Weasel
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RCinFLA
Solar Wizard
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There is a lot of 'snake oil' out there with regards to reviving lead-acid batteries.
Lead-acid batteries need to be kept charged to avoid discharged lead-sulfate from crystalizing which is near impossible to recharge. Initially after discharge, lead-sulfate is soft brown mossy texture, but after a few weeks to few months it hardens to tough crystals.
Equalize mode on lead-acid chargers run a 'controlled' overcharge up to about 16v on a 12v six cell lead-acid battery to force more charge current into battery.
Partially hardened lead-sulfate may break down and recharge given enough recharging current. If totally hardened lead-sulfate crystals, the next best thing is the vigorous bubbling of equalization charge can knock off the lead-sulfate crystals allowing them to sink to bottom of battery. This at least gives a fresh lead surface of battery plates. The lead-sulfate crystals that break off and sink to bottom of battery take sulfur with them so electrolyte acid concentration will remain low, showing low specific gravity measurements of electrolyte.
Equalization eats up a lot of water from electrolyte that must be replenished. It turns water into oxygen gas from positive plates and hydrogen gas from negative plates. Be well ventilated to avoid hydrogen gas build up or things can get exciting. Sealed lead-acid batteries cannot be equalized too much as replacement water cannot be added. They will vent gas via a pressure relief port if too much gas pressure builds up.
There are some semi-legit desulfators, although I have never seen much improvement in a heavily sulfated battery. These desulfators have a low frequency DC to DC boost/buck converter that pulses short high current pulses followed by a short discharge pulses.
It is claimed the pulsing rate of charge pulse / discharge pulse will recharge or knock off lead-sulfate without the stress of a full equalization charge. I have not seen any reliable research that independently verifies the claims. The peak current of pulses and the pulse rate would likely depend on size and condition of battery so a 'one size fits all' desulphator does not make practical sense.
Lead-acid batteries need to be kept charged to avoid discharged lead-sulfate from crystalizing which is near impossible to recharge. Initially after discharge, lead-sulfate is soft brown mossy texture, but after a few weeks to few months it hardens to tough crystals.
Equalize mode on lead-acid chargers run a 'controlled' overcharge up to about 16v on a 12v six cell lead-acid battery to force more charge current into battery.
Partially hardened lead-sulfate may break down and recharge given enough recharging current. If totally hardened lead-sulfate crystals, the next best thing is the vigorous bubbling of equalization charge can knock off the lead-sulfate crystals allowing them to sink to bottom of battery. This at least gives a fresh lead surface of battery plates. The lead-sulfate crystals that break off and sink to bottom of battery take sulfur with them so electrolyte acid concentration will remain low, showing low specific gravity measurements of electrolyte.
Equalization eats up a lot of water from electrolyte that must be replenished. It turns water into oxygen gas from positive plates and hydrogen gas from negative plates. Be well ventilated to avoid hydrogen gas build up or things can get exciting. Sealed lead-acid batteries cannot be equalized too much as replacement water cannot be added. They will vent gas via a pressure relief port if too much gas pressure builds up.
There are some semi-legit desulfators, although I have never seen much improvement in a heavily sulfated battery. These desulfators have a low frequency DC to DC boost/buck converter that pulses short high current pulses followed by a short discharge pulses.
It is claimed the pulsing rate of charge pulse / discharge pulse will recharge or knock off lead-sulfate without the stress of a full equalization charge. I have not seen any reliable research that independently verifies the claims. The peak current of pulses and the pulse rate would likely depend on size and condition of battery so a 'one size fits all' desulphator does not make practical sense.
efficientPV
Solar Addict
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(but the battery never went below 2.09 volts)
A perpetual energy source! You must have blinked. My town has an unofficial battery exchange at recycling and I've played around with reviving batteries. My greatest success seems to be with lead batteries which read less than 10mv. My water heater has jumper cables connected to it for pulsing the battery.
A perpetual energy source! You must have blinked. My town has an unofficial battery exchange at recycling and I've played around with reviving batteries. My greatest success seems to be with lead batteries which read less than 10mv. My water heater has jumper cables connected to it for pulsing the battery.
RCinFLA
Solar Wizard
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2.45v cell voltage is just normal absorb charge voltage. Equalization is about 2.60v per cell. Discharging first gives greater initial recharge current which helps recharging not totally hardened crystals. The initial recharge current will fizzle out quickly if battery is sulfated. If you repeat the discharge/recharge many times you may gain a slight amount of capacity, but not usually much.
I cannot believe someone would actually submit a PhD thesis just regurgitating info that has been known for 100 years on lead acid batteries. I see no claims of new information in the paper. A PhD thesis is supposed to show some innovation.
efficientPV
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Our company newsletter had an article in the 70's about how small a cube they could make a fast high current battery charger. They claimed if you periodically did a short high current discharge that bubbles on the plated would collapse. I've never seen that in anything since. I have to accept that it was true since it came from one of the worlds top 100 R&D centers.
Very interesting!
I have now charged the battery at 10 amp power for 17 hours. I can't try more than 10 amp power because the power supply is limiting. However, it seems to receive power much better than before, the voltage is now 2.32v when charging. The battery is cool and does not boil/gas.
Previously, the charging amperes started to decrease after 10 hours of charging.
Maybe this will be functional enough. I can't say about the lifespan ?
I might boil off the excess liquid and if it doesn't work like the other cells, I might add acid (EDTA dilutes acid)
Previously, the charging amperes started to decrease after 10 hours of charging.
Maybe this will be functional enough. I can't say about the lifespan ?
I might boil off the excess liquid and if it doesn't work like the other cells, I might add acid (EDTA dilutes acid)
I tried using the battery. It was better and had more capacity, but not enough.
I will try the same process again
I drained the battery and reverse charged it. This time the polarity did not want to reverse. I charged the battery in reverse for several days. Finally, the battery started to warm up slightly. The heating started from the top of the battery moving to the bottom of the battery.
After that, the battery cooled down and the polarity started to reverse. I read that the warming is part of the process that belongs to the removal of sulfate and the process can stay up independently and sometimes destroy the battery if there is no additional cooling.
I fully charge the battery in reverse and after that I discharge it this time with low amps and charge full.
We'll see. If there is no improvement, I will give up.
I will try the same process again
I drained the battery and reverse charged it. This time the polarity did not want to reverse. I charged the battery in reverse for several days. Finally, the battery started to warm up slightly. The heating started from the top of the battery moving to the bottom of the battery.After that, the battery cooled down and the polarity started to reverse. I read that the warming is part of the process that belongs to the removal of sulfate and the process can stay up independently and sometimes destroy the battery if there is no additional cooling.
I fully charge the battery in reverse and after that I discharge it this time with low amps and charge full.
We'll see. If there is no improvement, I will give up.
Zwy
Solar Wizard
Would have been easier and faster to try a DC inverter welder. I've done it, the battery will get warm, this helps crack sulfation off the plates and remove stratification.
Zwy
Solar Wizard
Flooded lead acid only. AGM and others would probably vent electrolyte.
Small update. The battery has now been used alongside others and it works fine now. The resting voltage is a little lower and I suspect that the sq is a little lower than the others. I haven't added acid yet because it's a gel battery.
At worst, I got only 60Ah from a 330ah battery. after reverse charging the first cycle was 280Ah. This apparently works when you do it properly, I wouldn't have believed it. Next, I will test this on an 80ah car battery, whose capacity is only 12ah. EDTA, pulsing, desulphator have also been tried.
At worst, I got only 60Ah from a 330ah battery. after reverse charging the first cycle was 280Ah. This apparently works when you do it properly, I wouldn't have believed it. Next, I will test this on an 80ah car battery, whose capacity is only 12ah. EDTA, pulsing, desulphator have also been tried.
Nobodybusiness
Collecting the leftovers of the Great Sky Reactor.
Have you met modern day PHDs?
Vigo
Solar Addict
I read this post the first time around, but upon reading a second time im reminded of a few things:
- The one time i accidentally, only momentarily, shorted a 48v lead acid pack and instantly BLEW the vent caps off of one battery like friggin bullets.. the amount of RAPID bubble formation and pressure buildup surely jostled THE SHIT out of those plates.
- And secondly.. the mantis shrimp!?
- And further, the type of cavitation damage that can be seen on metal parts of fluid pumps.
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Zwy
Solar Wizard
I tried reverse charging once, the battery still had enough voltage it fried the charger. I tried putting the smoke back in the charger but I guess I didn't blow hard enough.
What started me on that path was reading a paper by some Indian student about reverse charging. I prefer the DC welder method.
