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
That is very good advice, providing your goal is to kill the cells entirely.
You should not completely discharge NiCd batteries. Read
http://www.repairfaq.org/ELE/F_NiCd_Battery.html#NICDBATTERY_005 for a
reasonably technical discussion of this and other properties of NiCds.
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
:Regardless, I will make sure my next drill uses Nimh
I got the NiCads because the drill came cheaper that way. It's true that
NiMH will have greater capacity. They say that the modern NiCads don't
have the memory effect, but I don't know if that's categorically true.
However, something to consider is the fact that NiMH will self-discharge
at a significantly higher rate than NiCads. For me, that's a very
important factor because most of the energy drain on my cordless drill
batteries is from sitting around, not from use. I think I'll stick with
NiCads for that reason.
If you are letting the thing sit around a lot, get lithium batteries. The
self-discharge of NiMH is overstated by many - they do discharge faster than
NiCd, but not outrageously so. Li Ion, OTOH, will stay charged for long
periods. However, the life of a Li battery is more closely tied to state of
charge than to number of charge/discharge cycles. If it sits around fully
charged a lot, it will not last as long as if it's allowed to sit around
:> :>:Regardless, I will make sure my next drill uses Nimh
:> :> I got the NiCads because the drill came cheaper that way. It's true that:> NiMH will have greater capacity. They say that the modern NiCads don't:> have the memory effect, but I don't know if that's categorically true.:> However, something to consider is the fact that NiMH will self-discharge:> at a significantly higher rate than NiCads. For me, that's a very:> important factor because most of the energy drain on my cordless drill:> batteries is from sitting around, not from use. I think I'll stick with:> NiCads for that reason.:>
:Do NiMH short out or fail if self-discharged,like NiCds?
:If not,then they can be stored,then simply charged up before use,-without
:needing to buy new packs.
I think Lion rechargables isn't practical for me. To answer Jim's
question, I think that Lion's will fail, charged or discharged. The life
expectancy isn't really (AFAIK) more than 2 years. So, in that category,
NiCads and NiMHs have Lion truly beat. Lion's life expectancy can be
significantly increased by storing them refrigerated, preferrably around
40% charged. Not terribly practical for a cordless drill, but that's
what I do with my digicam batteries. Even so, I don't expect them to
last more than 3 years in my refrigerator... will see.
If the Lion's lasted more than a couple of years they would be a
possible option. Add to that the fact that they are pretty expensive (I
haven't priced them against the others but I imagine they are
significantly more expensive) and they are 3rd on the list of
rechargable drill batteries for me.
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.
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