Battery memory on NiCad cordless drill

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.

--
Jim Yanik
jyanik
at
kua.net

Posted by Dan_Musicant on August 9, 2006, 11:33 am

:
:>
:>:Regardless, I will make sure my next drill uses Nimh
:>:batteries.
:>
:> 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.

Dan

Posted by on August 5, 2006, 7:02 pm

>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.

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.
--

Larry Wasserman Baltimore, Maryland
lwasserm@charm.net

Posted by John Henderson on August 5, 2006, 7:28 pm

lwasserm@fellspt.charm.net wrote:

> When all the cells are fully discharged, it becomes possible

> for one or more of them to go into a reversed polarity state.

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.

John

Posted by Al Bundy on August 5, 2006, 8:01 pm

> 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.

>> 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.

>> Dan

> then find a way of clamping the trigger down so as to

> completely drain the battery.

Long/joined twistie ties, tie wrap, string are a few ways.

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