Those old NiCad rechargeable batteries

jerry_njMay 5, 2005

I've "got a ton of them", mostly on on power hand tools. I've moved to NiMh on D cells and smaller.

I have had good life (shelf) on NiCad batteries until I purchased a Ryobi 14.4Volt tool set, including electronic fast charger and two batteries.

The tool is perhaps 1 to 2 years old, has seen occassional use, mostly the hand light being the use, and now both batteries have lost capacity. Yes, I know about the memory effect, perhaps to a fault. I have almost always made sure the battery was really down before recharging. This may be part of the problem. So, I've been recycling the batteries for a few days, letting them run down on "their own", with occassional use of the hand light. Then recharge. They seem to be improving slightly.

Any experience/expertise on this subject? In particular I am of the opinion that Ryobi either got a bad batch of batteries, or there's something wrong with the charger.

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It's entirely possible that the batteries could have been weak from the start. A lot of times when you buy stuff like that you have no idea how long it's been sitting on the shelf, and if those batteries sit for a very long time, they can lose some of their life.

The charger may be okay but it may not be a smart charger. Take a look at the instructions and see whether they say it's okay to leave the batteries on the charger constantly. If they say that's okay, it's got circuitry in it to shut down the charge after the battery is fully charged. If they say not to charge the battery for any more than so many hours, the charger has no such circuitry, and you can do the battery in by leaving it on there too long.

Rechargeable batteries seem to like being used. If you let them sit too long unused, they often go bad on you.

One suggestion I'd have: If you plan to replace these batteries so you can keep using this tool kit, do it soon. One problem I've encountered with some cordless tools is that when you go to replace the batteries, you can no longer get them. I had a Bosch cordless drill I really liked that I had to junk because I couldn't get batteries for it. The batteries lasted about 7 years, so I can't complain, but I wish I could have found replacements.

    Bookmark   May 5, 2005 at 9:23PM
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Thanks, yes the charger is "smart", in fact it analyses the batter before it starts the fast charge. Good point on the replacement battery. I'll check to see if they are still available. I have a light, drill and small circular saw, and would like to keep them in operation. Funny thing on quality, I purchased a real "cheap" 9.6V battery powered drill from Harbor Frieght, I think it cost under $10. The battery and simple slow charge charger work great, the battery seems to have a lot of capacity and shelf life (i.e., has a very low leakage current).

    Bookmark   May 5, 2005 at 9:59PM
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The BatteriesPlus store will test your bateries for free to see if they are bad or not and can replace the cells inside ANY rechargable tool battery. cool. No, I don't work there or own stock...

    Bookmark   May 8, 2005 at 10:18PM
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I read an article in the past few months that completely draining NiCad batteries is actually bad for them. Drain them most of the way, but not all the way.

On a similar note, I bought a Black and Decker rechargable driver in 1994. I assumed it uses NiCad batts. I have kept it plugged in 24 hours per day every day since then and it still works great, 11 years later, with no noticable loss of capacity. Now THAT surprises me. I think it's a 9.6v with built-in, not replacable, batteries.

But those pleasant surprises only come along once in a while.

    Bookmark   May 10, 2005 at 12:22PM
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I had taken the subject batteries (14.4V) all the way down using the hand light. This was done in the belief that this is the only way to prevent the loss of capacity due to "memory effects". Seems that was the wrong thing to do. I have two batteries and they are both suffer from reduced capacity.

The "smart" battery charger in fact "tests" the battery before it starts charging. The insturctions say if the charger stays in the test mode, the battery is damaged. This indication did occur on the subject batteries, so I put them on a manual charge. After that the "smart" charger says they test okay, but the capacity is down more than 50%, I'd estimate.

I had considered sending a complaint to Ryobi, while the batteries are two years old, they have not seen much use, albeit always "full" use. I think now my discharge regiment may have been the problem.

    Bookmark   May 10, 2005 at 12:33PM
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In order to suffer damage to the battery by overly deep discharging, you have to run them REALLY low. Most devices won't even run them that low, becaue they'll quit working long before the battery is down really far. But, yes, with a light, you could run them very, very low if you kept it turned on for a long time after the light had gotten very dim. A light is about the only thing that would do that, though. A drill's motor would quit turning long before the battery was discharged extremely low, and anything electronic like a digital camera would shut down on its own when the voltage hit a certain level.

    Bookmark   May 10, 2005 at 5:23PM
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Good point, but the bad new is I may have used the light to discharge the battery and then forgot it was on for a day or two.

Both batteries appear to be okay from the charger performance. It takes about a hour for the charger to indicate fully charged. That energy is going somewhere, heat I suspect. The full charge measures about 15.4 volts, or about 1.3 volts per each of the 12 cells (nominal 1.2x12=14.4). This seems to me to suggest that all cells are taking a charge, i.e., I don't have a cell shorted or at zero volts. Still, the capacity is way down.

I saw on a Ryobi forum someone saying they'd had no luck at Home Depot in buying a replacement 14.4 battery. I may decide to buy one new battery so that I can continue to use the three 14.4V tools I have. I'll be sure not to discharge batteries with a light or a resistor in the future (but, I note I have done this for years and this is the first case of early battery failure I can recall).

    Bookmark   May 10, 2005 at 9:11PM
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I tried to revive some AA Ni-MH batteries by deep discharging them repeatedly in a portable radio that I left playing for days until they got so weak that the audio got distorted, and I had similarly unimpressive results. I can recharge them and they will play the radio for days on end at low volume, but the current demand of that little radio is very low, and it will tolerate voltage far below what you need to run something with a motor, or an electronic device like a camera. But they still work, and I can use them to run the radio, so I guess all has not been lost.

Maybe that Batteries Plus store suggested above would be a possibility. I may take that Bosch drill in there to see if they can do anything w/the batteries on that.

    Bookmark   May 11, 2005 at 1:31AM
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I have many Ryobi, Dewalt, PC, etc. tools 14.4V and up. The NiCads go bad after a time. Yes they establish a memory, but it should be insignificant - basically full charge to 90% or so. There is not a problem letting them drain down, although the Ryobi chargers require a small amount of "juice" to trigger the recharging circuit one you insert the battery into the charger.

The biggest problem I run into is dead cells. The 14.4 volt Ryobi units consist of 12 1.2V C sub cells, daisy chained - depending on the mfg of the cell will determine the overall capacity of the battery pack - generally from 1400 mAh to 2000 mAh. The packs are designed to function even if some cells die (this yields an open circuit within the cell providing no voltage, but allows the pack's circuit to continue to function at less voltage and less mAh). The batteries tend to stop working if more than 50% of the 12 cells are dead. If you're handy with a soldering iron and ohm meter you can take apart the packs and replace the dead sub cells - generally 1.2v 2000mAh Nicads are available online from $2-4 per. If you have more than 4 or 5 dead - it's probably cheaper to by a $25-27 pack from Home Depot.

Hope this helps a bit. Oh and the above only holds true for NiCad and NiMH - not Lithium Ion - that's a whole other Mr. Wizard lession of DC current. lol

    Bookmark   December 9, 2008 at 11:28AM
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