I have several little LED flashlights, 2 1/2" long and 7/8" in diameter,
and on one the pushbutton switch on the end broke. OK. But yesterday I notice that on another, my favorite one because the light was so bright,
even after I turned if off, it was still casting some light. I
unscrewed the end with the switch and the resistance, when the switch is
off if 168K ohms. Turned it on and off and it was 145K ohms. on the
200K ohm scale. On the 2M ohm scale, it was 1.7M ohms.
Even the lowest of these values seems to limit the crrent too much to
get light out of an LED. What do you think about all this .
I have several little LED flashlights, 2 1/2" long and 7/8" in diameter,
and on one the pushbutton switch on the end broke. OK. But yesterday I notice that on another, my favorite one because the light was so bright,
even after I turned if off, it was still casting some light. I
unscrewed the end with the switch and the resistance, when the switch is
off if 168K ohms. Turned it on and off and it was 145K ohms. on the
200K ohm scale. On the 2M ohm scale, it was 1.7M ohms.
Even the lowest of these values seems to limit the crrent too much to
get light out of an LED. What do you think about all this .
El 12/03/2026 a las 22:47, micky escribi?:
I have several little LED flashlights, 2 1/2" long and 7/8" in diameter,
and on one the pushbutton switch on the end broke. OK. But yesterday I
notice that on another, my favorite one because the light was so bright,
even after I turned if off, it was still casting some light. I
unscrewed the end with the switch and the resistance, when the switch is
off if 168K ohms. Turned it on and off and it was 145K ohms. on the
200K ohm scale. On the 2M ohm scale, it was 1.7M ohms.
Even the lowest of these values seems to limit the crrent too much to
get light out of an LED. What do you think about all this .
Modern hi-efficiency LEDs generate enough light to be visible with just
a few microamperes. The eye can see light with just a handful of photons >(think of viewing a star).
An open switch must have infinite resistance; humidity or external dirt
may got inside, or metallic powder fallen from the contacts may create a >path for the current. I have seen both cases.
In sci.electronics.repair, on Fri, 13 Mar 2026 17:01:22 +0100, Miguel
Gimenez <me@privacy.net> wrote:
El 12/03/2026 a las 22:47, micky escribi˘:
I have several little LED flashlights, 2 1/2" long and 7/8" in diameter, >>> and on one the pushbutton switch on the end broke. OK. But yesterday I
notice that on another, my favorite one because the light was so bright, >>> even after I turned if off, it was still casting some light. I
unscrewed the end with the switch and the resistance, when the switch is >>> off if 168K ohms. Turned it on and off and it was 145K ohms. on the
200K ohm scale. On the 2M ohm scale, it was 1.7M ohms.
Even the lowest of these values seems to limit the crrent too much to
get light out of an LED. What do you think about all this .
Modern hi-efficiency LEDs generate enough light to be visible with just
a few microamperes. The eye can see light with just a handful of photons
(think of viewing a star).
An open switch must have infinite resistance; humidity or external dirt
may got inside, or metallic powder fallen from the contacts may create a
path for the current. I have seen both cases.
Amazing. Does all this mean that in my case, I can leave the batteries
in the flashlight and it will still take months to run down the
batteries? Right now I feel obliged to stop using this light to not
waste decent batteries.
In sci.electronics.repair, on Fri, 13 Mar 2026 17:01:22 +0100, Miguel
Gimenez <me@privacy.net> wrote:
El 12/03/2026 a las 22:47, micky escribi?:
I have several little LED flashlights, 2 1/2" long and 7/8" in diameter, >>> and on one the pushbutton switch on the end broke. OK. But yesterday I
notice that on another, my favorite one because the light was so bright, >>> even after I turned if off, it was still casting some light. I
unscrewed the end with the switch and the resistance, when the switch is >>> off if 168K ohms. Turned it on and off and it was 145K ohms. on the
200K ohm scale. On the 2M ohm scale, it was 1.7M ohms.
Even the lowest of these values seems to limit the crrent too much to
get light out of an LED. What do you think about all this .
Modern hi-efficiency LEDs generate enough light to be visible with just
a few microamperes. The eye can see light with just a handful of photons >>(think of viewing a star).
An open switch must have infinite resistance; humidity or external dirt >>may got inside, or metallic powder fallen from the contacts may create a >>path for the current. I have seen both cases.
Amazing. Does all this mean that in my case, I can leave the batteries
in the flashlight and it will still take months to run down the
batteries? Right now I feel obliged to stop using this light to not
waste decent batteries.
On Fri, 13 Mar 2026 21:59:56 -0400, micky <NONONOmisc07@fmguy.com>
wrote:
In sci.electronics.repair, on Fri, 13 Mar 2026 17:01:22 +0100, Miguel
Gimenez <me@privacy.net> wrote:
El 12/03/2026 a las 22:47, micky escribi˘:
I have several little LED flashlights, 2 1/2" long and 7/8" in diameter, >>>> and on one the pushbutton switch on the end broke. OK. But yesterday I >>>> notice that on another, my favorite one because the light was so bright, >>>> even after I turned if off, it was still casting some light. I
unscrewed the end with the switch and the resistance, when the switch is >>>> off if 168K ohms. Turned it on and off and it was 145K ohms. on the
200K ohm scale. On the 2M ohm scale, it was 1.7M ohms.
Even the lowest of these values seems to limit the crrent too much to
get light out of an LED. What do you think about all this .
Modern hi-efficiency LEDs generate enough light to be visible with just
a few microamperes. The eye can see light with just a handful of photons >>> (think of viewing a star).
An open switch must have infinite resistance; humidity or external dirt
may got inside, or metallic powder fallen from the contacts may create a >>> path for the current. I have seen both cases.
Amazing. Does all this mean that in my case, I can leave the batteries
in the flashlight and it will still take months to run down the
batteries? Right now I feel obliged to stop using this light to not
waste decent batteries.
Maybe. Most of today's electronic gadgets have electronic on/off
switches instead of mechanical on/off switches. The mechanical on/off
switch does not allow any leakage current to flow in the off position. However, that's not always the case with electronic on/off switches,
which might draw some small current in the off position. In example
of this problem are the common commodity digital calipers. <https://www.youtube.com/watch?v=X04RN5kXGSc> <https://www.youtube.com/watch?v=avnA9ofDqhc> <https://www.youtube.com/watch?v=nxyBc_CL4dQ>
I have to store the calipers with the battery removed to prevent
battery discharge.
Flashlights have the same problem but to a much lesser degree. Leakage current from the coin cell found in digital calipers is a fairly large percentage of the battery capacity. It doesn't take long to totally discharge the coin cell. However, all my flashlights now use Li-Ion batteries (18650 or larger). The same leakage current is a tiny
fraction of the much larger battery capacity. You won't notice a few microamps of discharge current from a battery rated at 2 amp-hrs.
Also, Li-Ion cells have a very small self-discharge current. I charge
my Li-Ion flashlights and individual batteries to 100% SoC (state of
charge). They will self-discharge to about 95% in a few hours, 90% in
a month, and then stay at about 85% SoC essentially forever. <https://www.batteryuniversity.com/article/bu-802b-what-does-elevated-self-discharge-do/>
The actual performance numbers will vary substantially by battery
type, brand, temperature, etc making the above numbers an estimate (or guess).
If you want to use a high availability flashlight with an electronic
on/off switch, *MEASURE* the leakage current and calculate how long
the flashlight will be useable ( >75% SoC). If the switch discharge
the battery in less time you consider acceptable, either buy a better
battery (Lithium, Li-Ion, Li-Iron-Phosphate) or recharge (or rotate)
the battery on a schedule that insures you will always have a
functional flashlight.
More:
<https://www.candlepowerforums.com>
<https://budgetlightforum.com>
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