I have a Panasonic 12v (NiCads) cordless drill/driver with 2 batteries and it seems to me that the batteries aren't holding a charge very well. They are around 3-4 years old, lightly used. They seem to charge too quickly. If I leave them in the charger after the charger shows them as fully charged and let them trickle charge, will that top them up? I haven't been doing that.
Is this a loss of capacity of the batteries? Is there some way I can restore the capacity of the batteries? Any experience with these? Thanks for any ideas, info, suggestions, etc.
The traditional way to erase battery memory is to deep-cycle the battery. For a drill/driver, I would use it until the thing hardly turns at all, then find a way of clamping the trigger down so as to completely drain the battery. You want to get it as close to 0VDC as possible. After that, fully charge the unit and see if the memory has been erased.
Some chargers have a diagnostic or "tune-up" mode that may help if you leave the batteries in for an extended time, so it's worth trying. Unfortunately, at 3 to 4 years it would be common to see some degradation in the performance of a nicad, regardless of how much use they have had.
This is indeed the traditional way and it is also NOT a good idea. The "memory effect" is pretty much a myth for multicell nicads used in cordless power tools. Letting the batteries fully discharge is also potentially harmful to the battery. When all the cells are fully discharged, it becomes possible for one or more of them to go into a reversed polarity state. Once this happens that cell becomes permanently useless. For a good quality cordless tool with a "smart" charger (most any DeWalt, Makita, Milwaukee, etc.) the best place to keep a battery is in a plugged-in charger. For cheaper cordless tools (like Harbor Freight's) with a "dumb" charger, remove the battery after the recommended charging time.
I'd say it's an inevitable consequence of the fact that individual cells cannot be fully balanced for all charging parameters when assembled into a battery of cells.
The only way of ensuring maximum life from such a battery (where individual cells aren't accessible) is to do the occasional "equalization" charge, overcharging at a trickle rate until the weakest cell (the one which leaks the most charge) has had time to come up to full charge.
Dan_Musicant wrote in news: snipped-for-privacy@4ax.com:
some chargers are designed to be able to leave the pack in,some are not. You need to check your manual.
It's been my experience that for longest life,NiCds are best used often.(use it or lose it) Once you start storing them for long periods,their life decreases. NiCds also have a self-discharge rate;just sitting in storage,they discharge on their own.
A lot of good info here, but I have some also to offer.
The key problem is "lightly used" - that means the NiCd cells will develop a memory, unlike more modern ones. A memory of being charged, then leak-discharged, then trickle charged, etc, etc. The only good way around avoiding this, is using (as others have said) a discharge cycle (or use to flat) before recharging, and not leaving them flat.
The age of the cells has NOTHING to do with the expected performance, as long as you have cycled them properly. I have NiCd cells still working strongly from the mid nineties.
Draining a NiCd or NiMH cell completely means to remove essentially all the energy it contains. This requires discharging it to a cell voltage of about 1.0 volt. Doing this, then recharging, is the way to reverse "memory" (voltage depression) effects. If the battery has 6 cells or fewer and they're reasonably well matched, you can usually safely discharge the battery to 1.0 volt times the number of cells (e.g., 6.0 volts for a 6 cell battery) without risk of reverse charging one of the cells. If the battery has more cells, this becomes increasingly risky and the only safe way to do it is to discharge the cells in groups of
4-6. This of course requires getting into the battery pack.
The folks cautioning against trying to discharge down to 0 volts are absolutely correct. It just about guarantees reverse charging one or more cells, which will permanently damage those cells. Those cells will then have even more reduced capacity, so they'll go into reverse charge even earlier in the battery cycle the next time. There's never any need to discharge a cell below 1.0 volt. A well designed tool or electronic device intended for NiCd or NiMH power should quit operating and drawing battery current when the pack voltage reaches 1.0 volt per cell. Unfortunately, a lot aren't in this category.
What the hell do I know? I've only been successfully doing this for years. Must be a fluke. At least I gave some advice that can actually work instead of just shooting down someone's advice.
If you don't use them much you need to keep checking the voltage at least once every 1-2 months and make sure the voltage doesn't drop below 12V. Full charge on a 12V NiCad is about
14V, but that degrades quickly to about 13V and I check the voltage when charging and stop before it reaches 14V. Overcharging is the number one cause of batteries going bad.
That's the problem with netnews and the Internet in general. Lot's of incorrect stuff that gets repeated over and over even by groups that should know better. Always check major manufacturers for the accurate information when there is controversial information.
I have two drills, a Makita and a Sears. The Makita is over 10 years old with the original two Batteries, the Sears is about 6 years old with the same two batteries. I always let the drill run down to where it stops turning or pretty close to stopping before recharging. Who knows, but it worked for me. I didn't do this at first, and after about 2 years one of the Makita batteries stopped holding a charge. From something I read on the internet (what the hell, it was worth a try) I took the 12 volts from my car battery charger and quickly touched it on the baterry contacts a couple times, sure enough the battery started working again, and it still works 8 years later! Regardless, I will make sure my next drill uses Nimh batteries.
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