Why do miniature flashlight lamps have such a low life rating?

[ITSME.ULTIMATE]

Often time, they're rated less than ten hours. Why do they have such a
short life?

 

[Robbie McFerren]

Compromise between efficiency and long life.
You can get flashlight size bulbs that last tens of thousands of hours,
but they are well under half the brightness.

I think they also compensate for overvolting. Two cells = 3.0 volts at
start but to obtain decent brightness throughout life of the batteries
the bulbs are rated at 2.2 volts. The lifeline of a typical
carbon-zinc/Zinc-Chloride (heavy duty)/alkaline cell is:
~1.5V---------->0.9 volts. That is per the rating per cell. This
overvolting causes an issue if someone wants to use lithium batteries as
they retain approx. 1.5 volts per cell (photo lithium) until death.
This causes the 2.2 volt bulb to run at about 3 volts throughout the
life of the batteries.

Just for reference here are how the common battery types will work for
voltage:

Carbon Zinc: 1.5 to 0.9 volts per cell
Zinc Chloride: 1.5 to 0.9 volts per cell
Alkaline (both RAM and regular): 1.5 to 0.9 volts per cell
Photo Lithium: Approx 1.5 volts per cell throughout life
NiCD: 1.2 volts / cell for 80% charge then stops at 0.8 at End
NiMH: 1.2 volts / cell for 80% charge then stops at 0.8 at end

Non-Flashlight batteries for reference:
-Lead Acid: 2 volts per cell (2.1 when charging) MUST STOP DISCHARGE at
1.75 volts / cell!
-Coin (regular) Lithium: Approx 3.0 volts per cell throughout life
(available in "D" size with appropriate shunts)
-LiON: 3.6 (also referred to as 3.7) volts / cell DISCHARGE MUST
TERMINATE AT 3 VOLTS / CELL CHARGE MUST TERMINATE AT 4.0 VOLTS / CELL
-LiPO: Very similar to LiON

Sorry about being offtopic, but I wanted to include battery data, for
more info visit sci.chem.electrochem.battery

 

[Bob]

Just for reference here are how the common battery types will work for
voltage:

Non-Flashlight batteries for reference:
-Lead Acid: 2 volts per cell (2.1 when charging) MUST STOP DISCHARGE at
1.75 volts / cell!

Correction.... You will NEVER charge a Lead-Acid battery at 2.1 Vpc.
Depending on chemistry, float is betwen 2.17, and 2.30 Vpc.

 

[JohnR66]

Often time, they're rated less than ten hours. Why do they have such a
short life?

What Ian said. You may have noticed how much whiter the flashlight bulb is
compared to a mains fed lamp. The short filament can take the heat better as
well.

While I'm at it, When I buy a new 2 cell flashlights, I ususally remove the
battery draining .75 amp Krypton bulb and install a PR-6 that draws 300 some
ma. In most cases, I need better run time than high brightness. The PR-6 may
be more efficeint with batteries anyway because the cell voltage drops
faster with the krypton bulb that it is runing in a lower effeciency state.
I don't use the more common PR-4 bulb because the rated bulb voltage is
lower and it burns out quickly.

I use a Xenon gas filled bulb rated at .5 a give the good mix of runtime and
brightness in C and D cell flashlights.

LED flashlights are the best. As the voltage drops, the light output does
not drop as fast since incandescence is not relied upon to produce the
light. My Luxeon white LED Dorcy that uses 3 AAA is my favorite flashlight.
My 4 D cell Mag light with .5 Xenon bulb is the brightest, but to heavy to
take everywhere.
John

 

[Don Klipstein]

Non-Flashlight batteries for reference:
-Lead Acid: 2 volts per cell (2.1 when charging) MUST STOP DISCHARGE at
1.75 volts / cell!

More like supplying 2.1 volts per cell to a light to moderate load when
fully charged, and has a voltage of about 2.35-2.4 volts per cell during
charging when approaching full charge and about 2.3-2.4 volts per cell
with charge being maintained (such as in a running automobile).

- Don Klipstein ([email protected])

 

[Robbie McFerren]

More like supplying 2.1 volts per cell to a light to moderate load when
fully charged, and has a voltage of about 2.35-2.4 volts per cell during
charging when approaching full charge and about 2.3-2.4 volts per cell
with charge being maintained (such as in a running automobile).

- Don Klipstein ([email protected])

I think you're right on this one, thanks, I don't deal with batteries
other than in consumer devices.

 

[David Peters]

What Ian said. You may have noticed how much whiter the
flashlight bulb is compared to a mains fed lamp. The short
filament can take the heat better as well.

While I'm at it, When I buy a new 2 cell flashlights, I ususally
remove the battery draining .75 amp Krypton bulb and install a
PR-6 that draws 300 some ma. In most cases, I need better run
time than high brightness. The PR-6 may be more efficeint with
batteries anyway because the cell voltage drops faster with the
krypton bulb that it is runing in a lower effeciency state. I
don't use the more common PR-4 bulb because the rated bulb
voltage is lower and it burns out quickly.

I use a Xenon gas filled bulb rated at .5 a give the good mix of
runtime and brightness in C and D cell flashlights.

LED flashlights are the best. As the voltage drops, the light
output does not drop as fast since incandescence is not relied
upon to produce the light. My Luxeon white LED Dorcy that uses 3
AAA is my favorite flashlight. My 4 D cell Mag light with .5
Xenon bulb is the brightest, but to heavy to take everywhere.

Can I repost something I aksed here recently but go no replies to.
It seems quite closely related to the topic for this thread....


Is the "K2" designation on a flashlight bulb an indication of its
current consumption?

All I can find is this:

"Rayovac introduced the krypton flashlight lamp to
the mass market. We gave these new numbers, K-1, K-2,
K-3, K-4, and K-13. These lamps are now industry
standards, and are identified as KPR-102, KPR-113, etc."
<http://www.rayovac.com/flashlight/bulbs.htm >

Can someone tell me what K2 (and K3, K4, etc) actually refers to?

 

[Don Klipstein]

Can I repost something I aksed here recently but go no replies to.
It seems quite closely related to the topic for this thread....

Is the "K2" designation on a flashlight bulb an indication of its
current consumption?

All I can find is this:

"Rayovac introduced the krypton flashlight lamp to
the mass market. We gave these new numbers, K-1, K-2,
K-3, K-4, and K-13. These lamps are now industry
standards, and are identified as KPR-102, KPR-113, etc."
<http://www.rayovac.com/flashlight/bulbs.htm >

Can someone tell me what K2 (and K3, K4, etc) actually refers to?

These refer to krypton-filled versions of the original industry-standard
PR2, PR3, PR4, etc.
I do not know if current consumption of the krypton-filled versions is
standardized, but I have seen current specifications indicating more
current than the PR types draw.
It appears to me that the PR ones draw mostly close to half an amp (less
for the PR4, a lower current version of the PR2) and the krypton versions
draw about 1/4 amp more than the original versions do.

- Don Klipstein ([email protected])

 

[David Peters]

These refer to krypton-filled versions of the original
industry-standard
PR2, PR3, PR4, etc.
I do not know if current consumption of the krypton-filled
versions is
standardized, but I have seen current specifications indicating
more current than the PR types draw.
It appears to me that the PR ones draw mostly close to half an
amp (less
for the PR4, a lower current version of the PR2) and the krypton
versions draw about 1/4 amp more than the original versions do.

Thanks for the reply Don.

 

[David Peters]

Often time, they're rated less than ten hours. Why do they have
such a short life?

10 hours?

That seems amazingly short. There isn't a missing zero is there?

 

[David Peters]

Non-Flashlight batteries for reference:
-Lead Acid: 2 volts per cell (2.1 when charging) MUST STOP
DISCHARGE at 1.75 volts / cell!

What happens if you go below this voltage on a car battery?

For example, a battery which gets run down because a lamp is left on
for a day or two while the car is not used.

 

[Robbie McFerren]

10 hours?

That seems amazingly short. There isn't a missing zero is there?

Nope, the highest I've seen for a flashlight bulb is 40 hours. That's
why I stick with LEDs as much as possible.

 

[David Peters]

Once or twice, charged promptly probably won't kill it.

(I have a battery in my car, that when I went to it in the
morning, it read 8mv, after charging, it started the car without
problems, and has for several months)

8mv ??

 

[David Peters]

I'm sure I've seen 2 hours quoted.

{{{ swoon! }}}

 

[Ian Stirling]

8mv ??

That was my reaction, on looking at the voltmeter.

I was surprised it came back.

 

[Ian Stirling]

8mv ??

That was my reaction, on looking at the voltmeter.

I was surprised it came back.

(that was under load, I hadn't disconnected the headlamps)

 

[Don Klipstein]

{{{ swoon! }}}

PR2 15 hours
PR3 15 hours
PR4 10 hours
PR6 30 hours
PR7 30 hours
PR12 15 hours
PR13 15 hours
PR18 3-5 hours depending on source

14 15 hours
112 5 hours
222 5 hours

HPR50 25 hours
HPR51 25 hours
HPR52 10 hours
HPR53 25 hours
HPR54 15 hours
HPR55 15 hours

- Don Klipstein ([email protected])