What is "parasitic drain" and is it important ?
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Alaric Darconville
Flashlight Enthusiast
Re: Technical question
That's most likely 8μA, or 8 microamps (8 millionths of an amp, 0.000008A). That's a tiny, tiny amount and is probably lost in the noise of the cells' self-discharge rate.
saypat
Enlightened
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- Jul 12, 2011
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Re: Technical question
must be nice worry about that. I got my UC15 the other day and I don't have lockout mode. I even got 10440 cells from the manufacture themselves that don't work. They are button tops, barely, and too short. They need a solder blob on them. It's a quality light, get finish, nice colors, great tint. Only wish I would have received the latest version of firmware.... would have been nice mo have a moonlight and electronic lockout.
must be nice worry about that. I got my UC15 the other day and I don't have lockout mode. I even got 10440 cells from the manufacture themselves that don't work. They are button tops, barely, and too short. They need a solder blob on them. It's a quality light, get finish, nice colors, great tint. Only wish I would have received the latest version of firmware.... would have been nice mo have a moonlight and electronic lockout.
archimedes
Flashaholic
Re: What is "parasitic drain" and is it important ?
... Title edited to include meaningful topic info ...
Probably this thread would be better placed in Flashlight Electronics / Batteries subforum, but we'll leave it here for the time being ....
... Title edited to include meaningful topic info ...
Probably this thread would be better placed in Flashlight Electronics / Batteries subforum, but we'll leave it here for the time being ....
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Re: What is "parasitic drain" and is it important ?
Thanks X2
If it has lockout, does that halt the drain?
Thanks X2
If it has lockout, does that halt the drain?
Timothybil
Flashlight Enthusiast
Re: What is "parasitic drain" and is it important ?
Unfortunately, manufacturers usually will not address the issue of parasitic drain. We normally have to depend on our fantastic reviewers like Selfbilt, SubWoofer, and HKJ to inform us, and sometimes it just isn't possible to measure due to the construction of the light. Since I could probably be called a Nitecore fanboy, I know that with at least several of their lights they have stated in the user manual how long a set of cells could be expected to last while the light is off, and how long when the light is in lockout. Other than that, you will just have to read the comments by other users. If the drain is considered to be too much you can bet that that fact will be brought up somewhere on CPF.
No, it doesn't halt the drain. The circuitry still has to watch for the sequence that ends the lockout. But apparently it doesn't take as much effort by the driver circuitry to watch for that so for almost all lights lockout mode does severely cut down on the parasitic drain. There have been exceptions. One light that came out a couple of years ago had the parasitic drain actually get worse when the light was put into lockout. Needless to say there soon was a new generation of that light that fixed that problem.
Unfortunately, manufacturers usually will not address the issue of parasitic drain. We normally have to depend on our fantastic reviewers like Selfbilt, SubWoofer, and HKJ to inform us, and sometimes it just isn't possible to measure due to the construction of the light. Since I could probably be called a Nitecore fanboy, I know that with at least several of their lights they have stated in the user manual how long a set of cells could be expected to last while the light is off, and how long when the light is in lockout. Other than that, you will just have to read the comments by other users. If the drain is considered to be too much you can bet that that fact will be brought up somewhere on CPF.
Re: What is "parasitic drain" and is it important ?
If the parasitic drain is only a few microamps, I wouldn't sweat it... the cell probably self discharges more than that. If it's hundreds of microamps or into the milliamp range, then it's more of a problem and you'll have to remove the battery or unscrew the tailcap when not using the light so you don't have a dead battery down the road. Chances are unless it's a really cheap piece o'junk light, it's not going to have that much parasitic drain anyway.
Some forms of parasitic drain are caused by the circuitry itself... anything in the circuit that draws power constantly, such as a pull-up resistor that has something "pulling down" on it for example, or a filter capacitor that has some leakage current, or any contaminants on the circuit board. The microcontroller may draw a small amount of power as well, depending on whether the firmware implements the sleep mode properly or not. If the UI is handled with interrupts, the controller can go into a full sleep where the clock stops completely and no circuits are switching, this results in virtually no parasitic drain from the microcontroller. If it's handled with polling, it still has to poll so it can sense when the button is pressed--this requires some sort of clock to be running, usually at a reduced frequency when in standby... sometimes a low frequency watchdog timer is used to allow the controller to sleep and only awaken a few times a second to poll the switch.
It's likely that most, if not all lights with soft switches use interrupts, though it's possible some cheap lights may still poll. If there's a lockout feature in the firmware, ideally it should go into a "deeper" sleep mode if one exists compared to normal off/standby. Of course, physically disconnecting the battery by unscrewing the tailcap eliminates all parasitic drain within the light... then you only have cell self discharge to worry about.
If the parasitic drain is only a few microamps, I wouldn't sweat it... the cell probably self discharges more than that. If it's hundreds of microamps or into the milliamp range, then it's more of a problem and you'll have to remove the battery or unscrew the tailcap when not using the light so you don't have a dead battery down the road. Chances are unless it's a really cheap piece o'junk light, it's not going to have that much parasitic drain anyway.
Some forms of parasitic drain are caused by the circuitry itself... anything in the circuit that draws power constantly, such as a pull-up resistor that has something "pulling down" on it for example, or a filter capacitor that has some leakage current, or any contaminants on the circuit board. The microcontroller may draw a small amount of power as well, depending on whether the firmware implements the sleep mode properly or not. If the UI is handled with interrupts, the controller can go into a full sleep where the clock stops completely and no circuits are switching, this results in virtually no parasitic drain from the microcontroller. If it's handled with polling, it still has to poll so it can sense when the button is pressed--this requires some sort of clock to be running, usually at a reduced frequency when in standby... sometimes a low frequency watchdog timer is used to allow the controller to sleep and only awaken a few times a second to poll the switch.
It's likely that most, if not all lights with soft switches use interrupts, though it's possible some cheap lights may still poll. If there's a lockout feature in the firmware, ideally it should go into a "deeper" sleep mode if one exists compared to normal off/standby. Of course, physically disconnecting the battery by unscrewing the tailcap eliminates all parasitic drain within the light... then you only have cell self discharge to worry about.
Re: What is "parasitic drain" and is it important ?
Parasitic drain means that the flashlight uses energy from the battery when turned off.
I personally don't like parasitic drain at all. I prefer mechanical switches to turn off flashlights or untwist the body of the flashlight from the head to get rid of this "parasitic drain".
Although its minor draw from the battery, the problem is that every flashlight has different internals, some draw even a few mA from the battery. Therefore it's especially with lights that are not often used I always go for the mechanical lock-out or mechanical switch....
Parasitic drain means that the flashlight uses energy from the battery when turned off.
I personally don't like parasitic drain at all. I prefer mechanical switches to turn off flashlights or untwist the body of the flashlight from the head to get rid of this "parasitic drain".
Although its minor draw from the battery, the problem is that every flashlight has different internals, some draw even a few mA from the battery. Therefore it's especially with lights that are not often used I always go for the mechanical lock-out or mechanical switch....
Darth_Cholo
Newly Enlightened
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Re: What is "parasitic drain" and is it important ?
I always felt that on my very old old TK40 8AA light it was significant even on eneloops. Got a new Trunight TN4A with some powerex cells and it's not noticeable.
I always felt that on my very old old TK40 8AA light it was significant even on eneloops. Got a new Trunight TN4A with some powerex cells and it's not noticeable.
Grijon
Flashlight Enthusiast
Re: What is "parasitic drain" and is it important ?
Interesting; I have an old TK40 loaded with Eneloops that has been sitting for a couple of months - this afternoon I'll see how much energy it takes to top them off with my C9000s.
Interesting; I have an old TK40 loaded with Eneloops that has been sitting for a couple of months - this afternoon I'll see how much energy it takes to top them off with my C9000s.
Darth_Cholo
Newly Enlightened
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Re: What is "parasitic drain" and is it important ?
For some reason i never thought it could be the 8AA envelops that are 10 years old that could be the problem. I just couldn't see myself spending 25-40 dollars for brand new batteries for such an old light.
I've be interested in your test results!
For some reason i never thought it could be the 8AA envelops that are 10 years old that could be the problem. I just couldn't see myself spending 25-40 dollars for brand new batteries for such an old light.
I've be interested in your test results!
Grijon
Flashlight Enthusiast
Re: What is "parasitic drain" and is it important ?
Well, I have to start a test, ha ha, so it will be a while.
I have a TK41 and a TK45, both with relatively young and low-cycle Eneloops that have been married since coming out of the packaging. I didn't know how long these two lights (and 16 Eneloops) had been sitting, nor how much runtime they had on them. I believe just a function test after charging several weeks ago.
So if you want 'real' data, quit reading this post now and check back in 6 weeks, LOL.
For those that are interested in any and all information, it took ~100mAh per cell to top off all 16 Eneloops with my Maha C9000s. I'm going to check again in 6 weeks after being sure to not use the lights at all, after a refresh of the cells today and tomorrow.
Well, I have to start a test, ha ha, so it will be a while.
I have a TK41 and a TK45, both with relatively young and low-cycle Eneloops that have been married since coming out of the packaging. I didn't know how long these two lights (and 16 Eneloops) had been sitting, nor how much runtime they had on them. I believe just a function test after charging several weeks ago.
So if you want 'real' data, quit reading this post now and check back in 6 weeks, LOL.
For those that are interested in any and all information, it took ~100mAh per cell to top off all 16 Eneloops with my Maha C9000s. I'm going to check again in 6 weeks after being sure to not use the lights at all, after a refresh of the cells today and tomorrow.
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Grijon
Flashlight Enthusiast
Re: What is "parasitic drain" and is it important ?
And...now I realize that I have no TK40: I have a TK41 and a TK45. Anyone still interested, or should I abort?
And...now I realize that I have no TK40: I have a TK41 and a TK45. Anyone still interested, or should I abort?
Darth_Cholo
Newly Enlightened
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- Mar 2, 2018
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Re: What is "parasitic drain" and is it important ?
maybe It's time i got a new AA/aaa charger that measured charging capacity. I have a hobby charger perhaps I'll get a cell holder to charge nimh with it. . It does tell me the capacity charged. Will pop those batteries back in and wait.
-Alex
maybe It's time i got a new AA/aaa charger that measured charging capacity. I have a hobby charger perhaps I'll get a cell holder to charge nimh with it. . It does tell me the capacity charged. Will pop those batteries back in and wait.
-Alex
