Re: [BlindHandyMan] Reviving NiCd Batteries
Gill, this can work if individual cells in the pack are actually shorted. This is usually proven when after a charge attempt the pack voltage is down by 1.2 volts or some multiple of that. You're correct this must be done while monitoring the pack voltage and doing it in short bursts of time. I've actually done this with less current limiting, and that may help to burn through the whiskers internally that cause the shorts, but it increases the risk of overheating. It's much better to do it on individual cells but of course on packs you can't often get at them. I think you'll find the pack will not really get back to full capacity and will probably develop more shorts in the not very far future, but heck it gives you some more capacity on the pack. Tom Fowle
Re: [BlindHandyMan] Reviving NiCd Batteries
Gil, I wonder if a place like batteries plus could rebuild them more cheaply than buying the components? earlier, Gil Laster, wrote: > > >Somewhere I came across an article on the >Internet about reviving NiCd batteries (nickel >cadmium) that no longer hold a charge. The >method is to "jolt" them by applying a voltage >equal to or a little greater than the battery >rating. The current is to be 1-amp for >30-seconds. This dissipates a kind of chemical >cobweb in the battery that forms over time, >especially when the battery is used >infrequently, shorting it out. After the jolting >the battery is to be charged normally. > >I have a 5-year-old 18-volt drill that came with >two standard NiCd batteries. They worked well >for about 3-years and then began less faithfully >holding a charge, eventually becoming useless. >2-years ago A replacement NiCd battery was about >$60. This annoyed me because I originally paid >$80 for the drill kit and could go buy another >for about the same price. What a waste of a good >drill to trash it because of the price of >batteries, so I procrastinated. Today there is >no replacement battery available for the drill, >but I could rebuild the battery using individual >sub-C high capacity NiMh (nickel metal hydride) >batteries for about $65. A few days ago as a >last resort I tried the jolt method on the dead >batteries. It worked! It did, however, take four >charge/discharge cycles for the batteries to >reach full capacity. For a Power supply I used >my home's doorbell power supply transformer >(estimated 1-amp capacity, transformers are >current self-limiting),a full wave bridge >rectifier, and 4-jumper leads. A talking volt >meter was used to make sure that I got polarity correct. > >Caution: Current must be limited in amount and >duration. Too much could cause overheating or worse, an explosion. > >- Gil Laster, Charlotte, NC > >[Non-text portions of this message have been removed] > > John [Non-text portions of this message have been removed]
[BlindHandyMan] Reviving NiCd Batteries
Somewhere I came across an article on the Internet about reviving NiCd batteries (nickel cadmium) that no longer hold a charge. The method is to "jolt" them by applying a voltage equal to or a little greater than the battery rating. The current is to be 1-amp for 30-seconds. This dissipates a kind of chemical cobweb in the battery that forms over time, especially when the battery is used infrequently, shorting it out. After the jolting the battery is to be charged normally. I have a 5-year-old 18-volt drill that came with two standard NiCd batteries. They worked well for about 3-years and then began less faithfully holding a charge, eventually becoming useless. 2-years ago A replacement NiCd battery was about $60. This annoyed me because I originally paid $80 for the drill kit and could go buy another for about the same price. What a waste of a good drill to trash it because of the price of batteries, so I procrastinated. Today there is no replacement battery available for the drill, but I could rebuild the battery using individual sub-C high capacity NiMh (nickel metal hydride) batteries for about $65. A few days ago as a last resort I tried the jolt method on the dead batteries. It worked! It did, however, take four charge/discharge cycles for the batteries to reach full capacity. For a Power supply I used my home's doorbell power supply transformer (estimated 1-amp capacity, transformers are current self-limiting),a full wave bridge rectifier, and 4-jumper leads. A talking volt meter was used to make sure that I got polarity correct. Caution: Current must be limited in amount and duration. Too much could cause overheating or worse, an explosion. - Gil Laster, Charlotte, NC [Non-text portions of this message have been removed]
