I bought a low quality LED flashlight. Put in 3 AA Memorex alkaline
batteries. After about an hour later, I picked up the flashlight and
its handle was HOT. The flashlight wasn't on. Took the batteries out, 2
of them are not hot and the last one was. (The middle one was a bit
warm, actually, due to contact with the third).

My question is, based on the limited info above, can you tell whether
the battery was defective or the flashlight? I guess it most likely be
the battery, but is it possible for a defective flashlight to create
this condition? If so, how.

Thanks.

wrote:
I bought a low quality LED flashlight. Put in 3 AA Memorex alkaline
batteries. After about an hour later, I picked up the flashlight and
its handle was HOT. The flashlight wasn't on. Took the batteries out, 2
of them are not hot and the last one was. (The middle one was a bit
warm, actually, due to contact with the third).

My question is, based on the limited info above, can you tell whether
the battery was defective or the flashlight? I guess it most likely be
the battery, but is it possible for a defective flashlight to create
this condition? If so, how.

Thanks.

Hi...

The flashlight is defective, the batteries are (or were)
fine.

Are you *sure* you didn't put one of them in backwards?

Ken

Ken,
I put the batteries in correctly. The flashlight worked.
How did you conclude that the FL was defective? I am ignorant WRT to
this matter.
Thanks,
Kathy

wrote:

Ken,
I put the batteries in correctly. The flashlight worked.
How did you conclude that the FL was defective? I am ignorant WRT to
this matter.
Thanks,
Kathy

Hi...

Not implying that all of the batteries were backwards, only
one out of the three. In which case there would still be
1.5 volts left, sufficient to light the led's and let the
light work for a while.

Three batteries connected in series, and sitting in a
turned off light, can't possibly do anything at all

Take the flashlight back; get yourself a refund or a new
one

Ken

Ken,

This is the arrangement I had:
Bulb [+AA -][+AA -][+AA -] The third battery from the bulb was hot.

Your explanation sounds perfectly logical to me. Just to confirm
though, in case I indeed made a mistake, if I have this arrangement:
Bulb [+AA -][+AA -][-AA +] then the third battery can become hot?

Kathy

wrote:

Ken,

This is the arrangement I had:
Bulb [+AA -][+AA -][+AA -] The third battery from the bulb was hot.

Your explanation sounds perfectly logical to me. Just to confirm
though, in case I indeed made a mistake, if I have this arrangement:
Bulb [+AA -][+AA -][-AA +] then the third battery can become hot?

Kathy

Hi...

Yeppers. The remaining two will be doing their best to
charge the one that's 'out of step'.

Ken

This theory is a nice one, except that it doesn't quite hold up. The 1.5v
remaining is not enough to light a red LED, let alone a blue or white one
which these flashlights usually use. Kathy does say that the light worked
....

Just for sport, I connected three batteries up with the third one ' wrong ',
and hung a red LED across the string. As expected, it did not light with
1.5v across it. I then substituted about 10 ohms worth of R across the
string, and measured about 85mA being drawn. Now this would be a pretty high
current for a LED flashlamp. With current being drawn through the battery
string, the voltage across the R remained at about 1.5v, and the voltage
polarity remained correct across each cell - as it must for the 1.5v of the
reversed cell to correctly subtract from the series'd 3v of the other two.

So effectively, I was drawing 85mA ' backwards ' through the third cell,
which I suppose you might consider as the two trying to charge the one. The
bottom line was that after leaving this arrangement for some time, there was
no appreciable temperature rise in any individual cell.

I would think that the problem is more likely to be a short occuring between
the case of the flashlamp, which is almost certainly common to the - end of
the furthest battery from the LED, and the upper + terminal of that cell.
This would leave 3v remaining, which may just be enough to get a blue LED
going ( VF typ = 3.2 to 3.5v ) and perhaps a white which has a VF a few
decimals higher yet. It would certainly be enough to get a high intensity
amber going. Bear in mind also that sometimes, these flashlamp devices have
some electronics in them to buck the voltage from the battery so that
several LEDs can be series connected. The short created across that cell
would cause a large current to be drawn from it, which would cause the cell
to hot up in the way described. Interesting theory problem. I'm not sure
that I can think of a mechanical way that such a short could occur, but it
would be present at all times, which would account for the hotting up, even
with the flashlamp switched off. More mileage in this one yet, methinks ...

Geoff

"Ken Weitzel" wrote in message
news:v6zGe.65880$5V4.59212@pd7tw3no...


wrote:

Ken,

This is the arrangement I had:
Bulb [+AA -][+AA -][+AA -] The third battery from the bulb was hot.

Your explanation sounds perfectly logical to me. Just to confirm
though, in case I indeed made a mistake, if I have this arrangement:
Bulb [+AA -][+AA -][-AA +] then the third battery can become hot?

Kathy

Hi...

Yeppers. The remaining two will be doing their best to
charge the one that's 'out of step'.

Ken

On 29 Jul 2005 15:30:00 -0700 wrote:

I bought a low quality LED flashlight. Put in 3 AA Memorex alkaline
batteries. After about an hour later, I picked up the flashlight and
its handle was HOT. The flashlight wasn't on. Took the batteries out, 2
of them are not hot and the last one was. (The middle one was a bit
warm, actually, due to contact with the third).

My question is, based on the limited info above, can you tell whether
the battery was defective or the flashlight? I guess it most likely be
the battery, but is it possible for a defective flashlight to create
this condition? If so, how.

This is just a guess, but it sounds like the hot battery was shorted
out in some way when it was installed in the flashlight. Did all the
batteries have their plastic film covers completely intact? Is there
any chance that there was some other piece of metal in there which
could have shorted out the battery.

I assume the 3 cells were all in a row. Which position was the hot one
in?

I believe all alkaline cells have the body + with the - terminal the
flat one at the rear. If the rear contact of the flashlight was poorly
designed, it might be able to short between the center - contact and
the rolled lip around it, which is +. If this is the case then you
either have to fix the contact or forget it.

In a normal flashlight you could fix this by putting all the cells in
backwards, because an incandescent bulb doesn't care about polarity,
but the LEDs DO care, so this won't work in this case.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

In article ,
says...
This theory is a nice one, except that it doesn't quite hold up. The 1.5v
remaining is not enough to light a red LED, let alone a blue or white one
which these flashlights usually use. Kathy does say that the light worked

But... Some LED flashlights have electronics in them. I have a CMG
Infinity Ultra that uses ONE AA cell. The electronics step up the
voltage to run the LED. Generally, the higher the frequence (red to
yellow to green to blue), the higher the voltage required. White is
sometimes blue with a phosphor.

Cool LED site:
http://ledmuseum.home.att.net/

--
If there is a no_junk in my address, please REMOVE it before replying!
All junk mail senders will be prosecuted to the fullest extent of the
law!!
http://home.att.net/~andyross

Durrr....

If you had read on to the bottom of my posting, you would have seen that I
already made the point about some LED flashlights having electronics in them
to buck the battery voltage ....


Geoff


"Andrew Rossmann" wrote in message
.net...
In article ,
says...
This theory is a nice one, except that it doesn't quite hold up. The 1.5v
remaining is not enough to light a red LED, let alone a blue or white one
which these flashlights usually use. Kathy does say that the light worked

But... Some LED flashlights have electronics in them. I have a CMG
Infinity Ultra that uses ONE AA cell. The electronics step up the
voltage to run the LED. Generally, the higher the frequence (red to
yellow to green to blue), the higher the voltage required. White is
sometimes blue with a phosphor.

Cool LED site:
http://ledmuseum.home.att.net/

--
If there is a no_junk in my address, please REMOVE it before replying!
All junk mail senders will be prosecuted to the fullest extent of the
law!!
http://home.att.net/~andyross

Thank you all for your comments.
I inspected the inside of the battery tube and the probability of a
shorted battery as Jim described is high.
The coil connector presses against a piece of metal which goes along
the length of the flashlight. The 'hot' battery also had its film cover
damaged (before or after the short, I don't know.)

Kathy SHORT, who does live up to her name. :-)

On 29 Jul 2005 15:30:00 -0700 in sci.electronics.repair,
wrote,
I bought a low quality LED flashlight. Put in 3 AA Memorex alkaline
batteries. After about an hour later, I picked up the flashlight and
its handle was HOT. The flashlight wasn't on. Took the batteries out, 2
of them are not hot and the last one was.

Excessive clamping force applied to battery end deforms battery case and
causes internal short from case to center electrode.

On 31 Jul 2005 22:06:42 -0700 wrote:

Thank you all for your comments.
I inspected the inside of the battery tube and the probability of a
shorted battery as Jim described is high.
The coil connector presses against a piece of metal which goes along
the length of the flashlight. The 'hot' battery also had its film cover
damaged (before or after the short, I don't know.)

You could try just wrapping some tape around the battery and trying it
again. The solution might be exactly that simple.

Kathy SHORT, who does live up to her name. :-)

;-)

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------