Revive your NiCd Batteries?

[Mt. Gomer]

Cary is 1010 and Kildaire, right where Cary confronts Holly Springs.
Also weekdays at North Hills works.

I live in North Durham but work at the American Tobacco Campus which is right off 147 next to the Bulls Stadium.

Travis

 

[ehpoole]

Although there are parts of this that I disagree with based on my past experience (I always found batteries that sat discharged for extended periods were more likely to grow crystals than fully charged batteries.... a fully charged battery will instantly vaporize any crystals that do form).

I'm a little hesitant to suggest car batteries due to the fact that a typical car battery can easily surge upwards of 1000A at typical ambient temperatures -- litterally arc-welding class current.

If you use car batteries, make sure you use a few feet something like 20 AWG wire to atleast act as a fusible link (it will burn up before your battery if you overdue things -- so do NOT hold onto the 20AWG wire!)

Electronics is a hobby of mine, so my preference was to use a benchtop power supply. That allowed me to control both voltage (usually 12V) and amperage (5-10A). If you need more current then that, i would actually step down in voltage (e.g. 6V @10-30A). You do need a voltage several times greater than the batteries normal potential, but amps is what will burn through the crystals. Any voltage much greater than what is needed just creates that many extra watts of heat.

You will litererally only apply the charge to the battery for at most 1/2 to 1 second at a time. You should then give the battery time to return to near room temperature before proceeding. If your initial pulses do not appreciably warm the battery, then you can increase your intervals to several seconds each. The most important thing is not to overheat the battery. You'll also want to perform an amp test on the battery after every other test, if the battery can source atleast a few amps of current for a few seconds, you're done. If the battery can not source atleast a few amps of current for a few seconds, then it is still internally shorted.

In multicell battery packs, you really need to reset each cell individually, otherwise you will unequaly charge the cells and create a charge imbalance in the system (the OK cells will charge, while defective ones will not, this will lead to inverted charges being applied to the weaker cells when you later discharge the pack. Ideally, after resetting each individual cell you would also charge each cell individually with a charging voltage of around 1.8-2.4VDC and you will want a current equal to 1/10th to 1/20th the Amp-Hour rating of the battery. If you have access to a low-voltage benchtop supply this is trivial. Otherwise you will want something like an old filament transformer (3V), a bridge rectifier, and a power resistor of around 10-Ohms (and several watts) to limit the charge rate. You'll charge the cell for about 20 hours typically.

No matter how many times you do this, you will never get the original capacity out of the battery once it has begun to deteriorate. More importantly, once these crystals start forming in a battery they seem to continue forming unless you constantly maintain the battery pack by regularly fully discharging it (discharge until you see/hear the first 'step-down' in motor speed or light intensity ... that's the point at which the first cell in the pack as reached zero voltage and you should discharge no further. Then promptly recharge the battery pack. NiCd batteries are always at their best when they are seemingly abused the most (e.g. 100% discharge, 100% recharge -- they do not like shallow charge/discharge cycles).

All of this info is predicated on the obvious disclaimer that just because I have done this over the years to squeeze a little extra life out of a battery -- especially during my earlier years -- does not mean it is good advice, nor recommended advice, for others to duplicate!

Do so at your own risk with appropriate safety precautions. I just realy don't recommend using car batteries and arc welders (battery chargers of under 20-30A are probably OK, but no larger!)

 

[pirate71]

Although there are parts of this that I disagree with based on my past experience (I always found batteries that sat discharged for extended periods were more likely to grow crystals than fully charged batteries.... a fully charged battery will instantly vaporize any crystals that do form).

I'm a little hesitant to suggest car batteries due to the fact that a typical car battery can easily surge upwards of 1000A at typical ambient temperatures -- litterally arc-welding class current.

If you use car batteries, make sure you use a few feet something like 20 AWG wire to atleast act as a fusible link (it will burn up before your battery if you overdue things -- so do NOT hold onto the 20AWG wire!)

Electronics is a hobby of mine, so my preference was to use a benchtop power supply. That allowed me to control both voltage (usually 12V) and amperage (5-10A). If you need more current then that, i would actually step down in voltage (e.g. 6V @10-30A). You do need a voltage several times greater than the batteries normal potential, but amps is what will burn through the crystals. Any voltage much greater than what is needed just creates that many extra watts of heat.

You will litererally only apply the charge to the battery for at most 1/2 to 1 second at a time. You should then give the battery time to return to near room temperature before proceeding. If your initial pulses do not appreciably warm the battery, then you can increase your intervals to several seconds each. The most important thing is not to overheat the battery. You'll also want to perform an amp test on the battery after every other test, if the battery can source atleast a few amps of current for a few seconds, you're done. If the battery can not source atleast a few amps of current for a few seconds, then it is still internally shorted.

In multicell battery packs, you really need to reset each cell individually, otherwise you will unequaly charge the cells and create a charge imbalance in the system (the OK cells will charge, while defective ones will not, this will lead to inverted charges being applied to the weaker cells when you later discharge the pack. Ideally, after resetting each individual cell you would also charge each cell individually with a charging voltage of around 1.8-2.4VDC and you will want a current equal to 1/10th to 1/20th the Amp-Hour rating of the battery. If you have access to a low-voltage benchtop supply this is trivial. Otherwise you will want something like an old filament transformer (3V), a bridge rectifier, and a power resistor of around 10-Ohms (and several watts) to limit the charge rate. You'll charge the cell for about 20 hours typically.

No matter how many times you do this, you will never get the original capacity out of the battery once it has begun to deteriorate. More importantly, once these crystals start forming in a battery they seem to continue forming unless you constantly maintain the battery pack by regularly fully discharging it (discharge until you see/hear the first 'step-down' in motor speed or light intensity ... that's the point at which the first cell in the pack as reached zero voltage and you should discharge no further. Then promptly recharge the battery pack. NiCd batteries are always at their best when they are seemingly abused the most (e.g. 100% discharge, 100% recharge -- they do not like shallow charge/discharge cycles).

All of this info is predicated on the obvious disclaimer that just because I have done this over the years to squeeze a little extra life out of a battery -- especially during my earlier years -- does not mean it is good advice, nor recommended advice, for others to duplicate!

Do so at your own risk with appropriate safety precautions. I just realy don't recommend using car batteries and arc welders (battery chargers of under 20-30A are probably OK, but no larger!)

Wow, that really made my head spin. Given that I am "electrically challenged" in the first place and in my 61 years I've probably already used up most of my "9 lives", I think I'll just let my old Porter Cable drill die of natural death when the time comes. Maybe this is one skill I don't need to master.:nah:

Thanks for all the discussion and for saving me from myself!!

 

[CarvedTones]

Wow, that really made my head spin. Given that I am "electrically challenged" in the first place and in my 61 years I've probably already used up most of my "9 lives", I think I'll just let my old Porter Cable drill die of natural death when the time comes. Maybe this is one skill I don't need to master.:nah:

Thanks for all the discussion and for saving me from myself!!

Just wanted to chip in that I am also not going to do anything with mine. It turns out that Travis had 3 batteries; 2 good ones and a bad one, and accidentally gave me the bad one. Fortunately he had not thrown out the other good one, so he will get it to me. Anyway, I am not sure if the bad one can be rescued or not, but I was only going to try this if it could be done with a low amperage converter. I also noticed that HD has them (Ryobi 14.4 NiCad) on the shelf for $30, which is cheaper than the online battery places, which leads me to a related question - what is the shelf life? I suspect that is a good price and that the battery will become harder to find in the future. It might be worth it to snag one for the future, if it would last.