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NIMH (rechargeable) and Alkaline non rechargeable

 
 
ASAAR
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      01-19-2007
On 18 Jan 2007 14:51:05 -0800, y_p_w wrote:

> Mag Lite flashlights specifically don't recommend the use of
> rechargeable batteries. I think part of the reason is that a NiMH
> cell starts off at 1.4V (at best) or maybe 1.3V a day after being
> charged. A fresh alkaline cell starts off at 1.6V. A light on a
> fresh set of alkalines will be brighter as a result. These are not
> high-drain devices where NiMH is more efficient.


One would think so, but that's not entirely the case. MagLites
specify a working voltage range, and while alkalines start out with
a higher voltage, through most of the battery's life the voltage
will be higher using NiMH batteries. This partially depends on how
the lights are used, and alkalines might appear to do a little
better if they're used for very short periods, since the voltage
"rebounds" when turned off, and for a short while after it is turned
on again, the voltage (and the brightness) will be a bit greater
than when it was turned off. If used for more than several minutes
at a time, alkaline voltages will noticeably sag. This is what I
like about MagLite's new LED lights. The lights (at least the one
I've used) stay bright and has a very white color (without the
bluish cast many LED lights have) even when the batteries aren't
fresh. With filament bulbs, flashlights, whether MagLites or other
brands, the light is bright and relatively white only with very
fresh batteries. Throughout most of their lives, the light output
gets weaker and weaker, and the color shifts from moderately white
to a yellowish cast. The working voltage range I mentioned, is only
specified for the non-LED MagLites. I couldn't find similar data
for the LED lights. MagLite sells several types of bulbs for their
flashlights. Some are more efficient than others, not only being
brighter, but also last slightly longer per set of batteries, if I
recall correctly. MagLite also sells replacement LED bulb modules
for their traditional models, but only for the C and D cell sizes,
not for the Solitaire and Mini models. What surprised me is that
the LED light can focus the beam the way traditional MagLites do. I
assume that this would also be true for older lights where the LED
modules are installed. The LED MagLites, btw, still include a spare
filament bulb in the base/end cap.


> The bulbs might also be designed with the internal resistance of
> alkalines in mind to maximize life. Just a thought. I've heard of
> some older camera flashes that would die when NiMH batteries
> were used because they were designed to use the internal resistance
> of alkalines as a current limiter.


I think that that was mainly a problem with NiCad batteries used
in cheap flashes that have no protective circuitry. It's not just
that they have very little internal resistance, which allows the
flash capacitor to be charged more quickly, overheating the flash
tube and other parts of the unit, but that (I believe) the NiCad
cells themselves, due to their chemistry, produce more heat than
other battery types. Better designed flash units allow only a
certain number of flashes within a predetermined period before they
stop operating temporarily (like from 15 to 30 minutes), allowing
the flash unit to cool off to a safe operating temperature.


> I have a Petzl LED headlamp, and the instructions state that
> NiMH rechargeables are acceptable. I'll almost always recharge
> them quickly before cell reversal can happen.


It would be nice if manufacturers stated why certain things are
recommended, allowed or prohibited. The way you use the Petzl is
wise, since although LED lights could be designed to prevent cell
reversal, my guess is that most aren't.


> I used NiMH AAAs in a Mag Lite Solitaire. Bad idea. It didn't mean
> cell reversal but constantly deep discharging the battery when the
> cap turned on in my pocket killed the capacity quickly.


That's odd. I almost always have a MagLite Solitaire in my pocket
and it has never accidentally turned on. It's only out of habit,
and I should have replaced it with something like a cheap Garrity
LED light (also single AAA) that performs much better. The only
advantage the Solitaire has is size. It's more compact, since it
doesn't flare out to a larger diameter at the "light" end. The
lights that cause me problems are the ones that although they have
very high quality pushbutton switches, the switches require only a
very light pressure to turn on. I noticed this one evening when on
taking the light out of a roomy coat pocket, noticed only a very
faint glow from the light's Luxeon LED. This model uses 3 AAA
cells, and at least it only wasted the 3 alkalines. If rechargeable
cells had been used, they probably would have needed to RIP.


> Low battery warning and/or protection diodes would help. That
> would require circuitry that would cost too much for the average
> flashlight.


Sears sells some Craftsman lights (2C, 3D and 4AA models) that
have 3 differently colored LEDs to help indicate battery voltage.
But they'd really be useful if used for voltage regulated lights.
In the Sears lights, the brightness of the lights themselves provide
a better indication of the battery voltage than the LEDs. I
replaced the filament bulb in one of the 4AA models with an LED bulb
removed from another similar 4 AA light, and the green LED (that
indicates high voltage) seems to be the only one that ever lights,
even doing so when the batteries aren't particularly fresh.


>> As for the "newer hi-powered flashlights" that Nick mentioned, the
>> only ones I'm aware of that use rechargeable batteries are models
>> used by police, firemen, military, etc., and they tend to use
>> proprietary NiCad or NiMH battery packs, not Li-Ion, and are usually
>> very expensive, costing several hundreds of dollars. That's not to
>> say that there aren't any Li-Ion models, but I haven't seen them.
>> What Nick may be thinking of are the multiple watt, *very* bright
>> LED lights that are designed to use non-rechargeable lithium
>> batteries. And it's not that they need to use lithium batteries, as
>> several manufacturers are now making high powered LED lights that
>> use alkaline batteries. The best ones use voltage regulators, so
>> that even as the alkaline battery voltages drop, the light output
>> doesn't fall off. I got one of the new MagLites about 6 months ago
>> and its output is today just as bright as they day I put the
>> batteries in it. These D cell batteries were removed from another
>> device because for it, the battery voltage was getting very low.

>
> Anything that expensive probably uses protection circuits to keep
> the batteries from cell reversal or deep discharge. Many have low
> battery indicators. Frankly it's a better idea because they can be
> topped off every night with a reasonable expectation of charge life.
> That would compare with alkaline cells that are left in until they run
> out, and without having a good idea how much battery life is there.
> Of course there could be something like a regular schedule where
> alkalines are replaced every other day, but that's rather wasteful.


Yep, and these lights are usually part of a "pool", where the cop,
fireman, etc. doesn't worry about taking care of the lights, which
are typically charged, maintained and periodically tested by someone
else. He/she just picks up a freshly charged light before heading
out for the shift. These lights (LED and otherwise) are advertised
as being useful as "weapons", since the brightness is high enough to
temporarily incapacitate whoever is unwise enough to look into the
light. The dim glow from dying alkalines just isn't the same. <g>

 
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Little Green Eyed Dragon
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      01-19-2007
In article <(E-Mail Removed)>,
Ron Hunter <(E-Mail Removed)> wrote:

> Generally, using the batteries recommended by the device manufacturer is
> the best choice.


Yes it is!!! and let me take this op to decry the F-wits I get stuff
back from in my four day PT job that can't RTFM....when it says Lithium
Batteries are not a recommended source.


--
Would thou choose to meet a rat eating dragon, or
a dragon, eating rat? The answer of: I am somewhere
in the middle. "Me who is part taoist and part Christian".
 
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Paul Heslop
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      01-19-2007
Dave Martindale wrote:
>
> Paul Heslop <(E-Mail Removed)> writes:
>
> >> Exception
> >> would be where the manufacturer states NIMH batteries should not be
> >> used. I once read that notice for an article I bought but now I can't
> >> remember what that article was.

>
> >I don't think I have ever seen that notice on anything, but then again
> >I might have just binned the instructions :O)

>
> I've seen it in two places: electronic flashes and handheld radio
> battery packs. In both cases, it's because NiCd and NiMH cells have
> much lower internal resistance, and thus can deliver much more current
> into a low-resistance load, than alkalines can.
>


I wonder if the warning is international? I really think I'm probably
just too lazy to look closely at stuff like flashlights, and as a rule
I tend to keep my NIMH just for the cameras, but I'll have to have a
look see next time I purchase something like this.

> If you short an alkaline cell, you'll get a few amps of current flowing -
> enough to make the cell get warm but not much more. If you short an AA
> NiCd cell, the current may be 10 amps or more. This is enough to damage
> the cell internally, melt smaller-gauge wire, and if it continues the
> cell may heat up rapidly enough to explode.


good grief. We had a lot of problems with two cordless phones
recently. when packing them to send them back I noted that they had
quite weak NiCd batteries which kind of surprised me as i expected
NiMh at least. Even after a complete overhaul they lasted only a few
more weeks... wonder if the batteries could have contributed to their
downfall.

>
> Many handheld radio transmitters are powered by battery packs containing
> NiCd or NiMH cells, and they always include a fuse or circuit breaker of
> some sort to protect the pack from exploding or catching fire if the
> terminals are accidentally shorted. Some manufacturers also sell AA
> battery packs for emergencies, and these packs are usually just a
> battery holder without any protective devices. The manufacturer's
> manual says to use alkalines only, because alkalines are safe without
> external circuit breakers. NiMH cells will fit fine and work well, but
> there is a fire hazard when you do it.


Now there's something I haven't taken a look at closely. personally
for those things, if I bought them I'd want rechargeable anyway so
they'd probably be NiCd at least.

>
> In the case of electronic flashes, there were once some flashes that
> depended on the battery internal resistance to limit the battery current
> during flash recharge. If you installed NiCd cells instead of alkalines
> (this was a long time ago), the current increased beyond the limits of
> the electronics, and the flash died.
>
> Dave


Strangely we have only just begun buying flashlights... must be
something to do with being over 50 :O)

--
Paul (Need a lift she said much obliged)
-------------------------------------------------------
Stop and Look
http://www.geocities.com/dreamst8me/
 
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Paul Heslop
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      01-19-2007
Little Green Eyed Dragon wrote:
>
> In article <(E-Mail Removed)>,
> Ron Hunter <(E-Mail Removed)> wrote:
>
> > Generally, using the batteries recommended by the device manufacturer is
> > the best choice.

>
> Yes it is!!! and let me take this op to decry the F-wits I get stuff
> back from in my four day PT job that can't RTFM....when it says Lithium
> Batteries are not a recommended source.
>

:O) We're sorry, we won't do it again



--
Paul (Need a lift she said much obliged)
-------------------------------------------------------
Stop and Look
http://www.geocities.com/dreamst8me/
 
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John Turco
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      01-21-2007
ASAAR wrote:

<heavily edited, for brevity>

> MagLite also sells replacement LED bulb modules
> for their traditional models, but only for the C and D cell sizes,
> not for the Solitaire and Mini models.


Hello, ASAAR:

I've bought third-party ("Nite Ize, Inc.") 3-LED/reflector upgrade
kits, intended for MagLite's AA flashlights.

(Haven't installed any of them, yet, incidentally.)

<edited>

> > I used NiMH AAAs in a Mag Lite Solitaire. Bad idea. It didn't mean
> > cell reversal but constantly deep discharging the battery when the
> > cap turned on in my pocket killed the capacity quickly.


The Solitaire is a very cute and capable puppy, and I formerly carried
one, on my keychain; I prefer the even smaller "no name" LED units, now.

<edited>

> Sears sells some Craftsman lights (2C, 3D and 4AA models) that
> have 3 differently colored LEDs to help indicate battery voltage.
> But they'd really be useful if used for voltage regulated lights.
> In the Sears lights, the brightness of the lights themselves provide
> a better indication of the battery voltage than the LEDs. I
> replaced the filament bulb in one of the 4AA models with an LED bulb
> removed from another similar 4 AA light, and the green LED (that
> indicates high voltage) seems to be the only one that ever lights,
> even doing so when the batteries aren't particularly fresh.


<edited>

I replaced a regular bulb with an LED, in a "dollar store" (2 AA)
clip-on light. Along with a tiny version (taking button cells), I
use it when working inside my computer.

Quite handy, indeed!

<edited>

> These lights (LED and otherwise) are advertised
> as being useful as "weapons", since the brightness is high enough to
> temporarily incapacitate whoever is unwise enough to look into the
> light. The dim glow from dying alkalines just isn't the same. <g>


A MagLite "D" would be a rather formidable "weapon" (the 4-cell model,
especially), if wielded as a club.


Cordially,
John Turco <(E-Mail Removed)>
 
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ASAAR
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      01-21-2007
On 20 Jan 2007 21:47:26 EST, John Turco wrote:

>> MagLite also sells replacement LED bulb modules
>> for their traditional models, but only for the C and D cell sizes,
>> not for the Solitaire and Mini models.

>
> Hello, ASAAR:
>
> I've bought third-party ("Nite Ize, Inc.") 3-LED/reflector upgrade
> kits, intended for MagLite's AA flashlights.
>
> (Haven't installed any of them, yet, incidentally.)


I got one of them several months ago, tried to install it in a
very old Mini and it's ok, but if MagLite comes out with their own,
it'll probably be much nicer - probably with regulated voltage like
the C and D cell models.


> I replaced a regular bulb with an LED, in a "dollar store" (2 AA)
> clip-on light. Along with a tiny version (taking button cells), I
> use it when working inside my computer.


Do you know Buster Brown or his dog Tige?


>> These lights (LED and otherwise) are advertised
>> as being useful as "weapons", since the brightness is high enough to
>> temporarily incapacitate whoever is unwise enough to look into the
>> light. The dim glow from dying alkalines just isn't the same. <g>

>
> A MagLite "D" would be a rather formidable "weapon" (the 4-cell model,
> especially), if wielded as a club.


No thanks, I don't need to join that club. I've got the 3 D cell
model, and the LED maintains high output so much longer than the
bulb models that I think the 2 or 3 C-cell version would be better.
I'd like to see a 4 D cell MagLite toss added to the Olympic Summer
Games. If an event has to be dropped to make this possible, umm,
how about making synchronized swimming disappear?


By the way, Radio Shack has joined Sanyo and RayOVac in offering
their own version of the Eneloop and Hybrid batteries. Unlike those
two companies, RS hasn't given it a new name, saying only that these
NiMH batteries are "precharged rechargeables". They have the same
2,000 mAh capacity as the Eneloops, but RS charges a lot more for
them, $20 for four. And for Ron if he's reading this, RS says that
they're compatible with any standard NiMH charger. I wonder if
their use of "standard" is designed to be a legal loophole?


P.S. I just ran this reply through the newsreader's spell checker,
and the first word it questioned was MagLite, with the first choice
for a replacement being "Aglitter".

 
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y_p_w
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      01-23-2007
Ron Hunter wrote:

> Use of NIMH batteries in more complex, and well-designed, devices is
> usually preferable to alkaline batteries due to cost factors.
> Generally, using the batteries recommended by the device manufacturer is
> the best choice. NIMH batteries, most of which have high values of
> 'self-discharge' aren't generally good candidates for devices which
> aren't used often, or which are used continuously over long periods
> (clocks).


Certainly one use of NiMH cells that's gotten the most publicity is
for hybrid internal combustion engine/electric motor cars. I've looked
into what is done to maximize the life of those expensive battery
packs. Part of the deal is a complex thermal management system with
temperature sensors and cooling fans.

The charging system tries to keep the batteries between 40-65% of a
full charge. When it gets down below that, a load is placed on the ICE
to charge it back up. Regenerative braking also charges the battery
with what normally would be lost as heat. So there are no deep
discharges and no full charges. I've heard that a full charge actually
has a detrimental effect on ultimate battery life. Of course there's
always a small amount of overcharging even with the best charging
systems when you try to reach maximum capacity. With this charging/
discharging scheme as well as thermal management a NiMH battery
can supposedly last hundreds of thousands of times longer than a
typical full charge and discharge to about 20% capacity use.

This is far different than the typical expectation for a camera
battery, cell phone, or notebook computer. Maximum use on a single
charge is a huge selling point. I can't really imagine a manufacturer
would convince many that their charger that's designed to charge only
to 75% capacity is in the best interests of the consumer. Just try
and tell the consumer that they need to only use about half of the
available capacity of their batteries in order to get 10-100 times more
useful life. Most people would settle for the convenience of
maximizing a single charge and replacing their batteries as needed.

 
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ASAAR
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      01-23-2007
On 23 Jan 2007 11:19:59 -0800, y_p_w wrote:

> With this charging/discharging scheme as well as thermal management
> a NiMH battery can supposedly last hundreds of thousands of times longer
> than a typical full charge and discharge to about 20% capacity use.


I'm sure that a typo crept in, and "hundreds or thousands of times
longer" was intended.


> This is far different than the typical expectation for a camera
> battery, cell phone, or notebook computer. Maximum use on a single
> charge is a huge selling point. I can't really imagine a manufacturer
> would convince many that their charger that's designed to charge only
> to 75% capacity is in the best interests of the consumer. Just try
> and tell the consumer that they need to only use about half of the
> available capacity of their batteries in order to get 10-100 times more
> useful life. Most people would settle for the convenience of
> maximizing a single charge and replacing their batteries as needed.


I agree. Manufacturers aren't inclined to do that. What they do
instead is have their chargers indicate that the batteries are
charged before the chargers have actually finished charging. Some
of my old RayOVac chargers indicated that charging was complete at
the point where the charge rate dropped from fast to slow (not quite
a trickle charge), and at that point the cells were only 85% to 90%
charged, and if left in the charger would complete charging several
hours later.

 
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y_p_w
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      01-23-2007

ASAAR wrote:
> On 23 Jan 2007 11:19:59 -0800, y_p_w wrote:
>
> > With this charging/discharging scheme as well as thermal management
> > a NiMH battery can supposedly last hundreds of thousands of times longer
> > than a typical full charge and discharge to about 20% capacity use.

>
> I'm sure that a typo crept in, and "hundreds or thousands of times
> longer" was intended.


Actually - I was thinking a combination of hundreds of thousands of
absolute cycle, as well as thousands of times longer, but made it
a combination of the two.

 
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ASAAR
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      01-23-2007
On 23 Jan 2007 13:09:48 -0800, y_p_w wrote:

>> I'm sure that a typo crept in, and "hundreds or thousands of times
>> longer" was intended.

>
> Actually - I was thinking a combination of hundreds of thousands of
> absolute cycle, as well as thousands of times longer, but made it
> a combination of the two.


Then don't think so hard! 365,000 qualifies as "hundreds of
thousands" on the fairly low end, and if the batteries are used
heavily enough to require a full charge every day of the year,
they'd last for 1,000 years. I doubt that marketing departments
addicted to the most hyperbolic copy would make such a claim. I
trust that you see why I thought that you meant something else. <g>

 
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