Why do some flashlights drain batteries when off, how to avoid?

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xtarflashlight
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Why do some flashlights drain batteries when off, how to avoid?

You may wonder why some flashlights drain batteries even when they are switched off and not in use. The batteries left inside the flashlights slowly lose charge, because of what is known as parasitic drain. And It’s important to know if the flashlights can store for months/years with batteries, or the batteries may be empty when the light is needed.

Most LED flashlights need a constant power supply in order to detect when it is being turned on. This constant power is what leads to parasitic drain. A general rule for detecting flashlights with standby power drain is to look after the switch, if it’s a non-locking switch, the light has a microprocessor that is always powered to control the power and for some lights they also need a running boost converter to power the microprocessor, which will increase the drain.

To prevent parasitic drain, one of the best ways is to remove the batteries from the flashlight when storing the flashlights for an extended period of time. Regardless of the power consumption, it’s always best to remove your batteries from the flashlights, which will completely stop this drain on the battery power, no matter of they are electronic switches or mechanical switches.

Edited by: sb56637 on 12/10/2021 - 07:22
tempo
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this is very important information, thank you for writing this article, you are my best!

Cochise334ever
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This has been talked about a lot over the years.

My lights that have three and four cell carriers, the batteries are out until use. Stored in large pill bottles with silica gel packets. My single cell lights I just twist the tail cap a little bit for the ones that have anodized threads. The other ones that I can not lock out,I just take out the battery until use.

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wle
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some drains enable features like
-lighted tail caps
-electronic switches

some drains can be due to poor design choices, either the firmware or the hardware

you do not have to run the microprocessor just because the light has one

it is possible for the micro to remain asleep, or in nA current mode, only being awakened by an interrupt from the switch

wle

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YuvalS
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wle wrote:
it is possible for the micro to remain asleep, or in nA current mode, only being awakened by an interrupt from the switch wle

Correct but nA will also drain the battery over long time especially a not fully charged one Sad  

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ChrisGarrett
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My D4V2 will go something like 6+ years with auxiliary lights set to low.

I remember reading of a particular Petzl HL draining a fresh cell in just a few weeks in the off position.

Chris

wle
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YuvalS wrote:

wle wrote:
it is possible for the micro to remain asleep, or in nA current mode, only being awakened by an interrupt from the switch wle

Correct but nA will also drain the battery over long time especially a not fully charged one Sad  

300mAH/10nA = 3425 years… !

"You never have the wind with you - it's either against you, or you're having a good day."
    Daniel Behrman, "The Man Who Loved Bicycles".
It never gets easy, you just go faster.   
-Greg Lemond.
       ,ø¤º°`°º¤ø¸,ø¤º°`°º¤ø¸,ø¤º°`°º¤ø¸

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