The There Are No Stupid Questions Thread

Might, but ain’t sure how the battery would react. It’s not a constant current, but 1% pulses of high current.

Not that I’m aware of.

Thanks for the responses. Guess I’ll go with a hobby charger to be on the safe side.

Wellp, if you get a 1A light (~1.05A for 3×7135), it’ll be a constant current until it starts to pull out of regulation and dims.

A $25 Liitokala Lii500 charger is well known for it ability to do capacity tests. It can discharge and recharge a cell and it’s results are good. That’s the cheapest I know of.

I’ll have to check on that been a while since I took inventory. Thanks!

Yeah I was looking at that as well. Sad that the UC4 hasn’t come out yet. I was hoping not to buy more chargers except the UC4. Thanks for the recommendation!

Another stupid question: how can I measure the draw from the tailcap leds in a lighted switch like those from Convoy?

I put one of the new ones (orange) in a 14500 flashlight, but I suspect it will draw too much power from the cell and can deplete it soon.

I never did that. I have a DMM and a clampmeter for that.

Any help is appreciated and thanks in advance :+1:

I will make a guess.

If the resistor that limits current and controls brightness of the led is on the same pcb that the led is on, you can wire a battery to the tail cap and measure current inline to see what the draw is.

If the current limiting resistor is on the driver board then it’s more tricky. Here is a basic drawing showing a flashlight circuit.

If you were to unsolder the red wire from the mcpcb you could then measure the current from the red wire to the flashlight body. This should measure everything between those two points minus the led and driver circuitry, but should include any resistors from the driver spring to ground, like shown below.

I have not actually tried it to see if I can measure tail cap led draw, though. It might work, but it can be a pain unsoldering the wire from the mcpcb.

You can pretty much assume any type of small colored LED is going to be a fairly High parasitic drain. So if you have a flashlight with a lighted tailcap or switch and you’re not going to be using it for at least a couple days, it’s best to just shut off all power. An easy way to get a rough estimate is to just measure the battery voltage, preferably not fully charged, and then let it sit a day or two and then see how much the voltage dropped. That will get you into the ball park.

The way I measure my lighted tailcap milliamps is by removing the head and taping a wire to the positive of the battery. And then attach the wire to the spring (positive) of the driver. Then touch 1 of the leads from the DMM to the threads of the body and the other to the retaining ring on the driver (or to threads on the head).

Here’s a pic of the milliamps of a white lighted tailcap in an S2+:

Thank you very much for your explanation and also the drawing to to help me understanding how that can be made.
The resistor is in the tailcap, the driver (1 mode) was from a cheappo flashlight I bought in a local store it has a handfull of components, only, so there is nothing there.

I let the battery inside from night to day and it apparently drew 0.02A. I guess it is quite high, but I wanted to be sure, because it is a 14500 cell, so it doesn’t have that much juice to be parasitically drained!

Thanks again for your time to explain!

Thank you very much for the photo demonstrating how you do it! I guess I can replicate that kind of “model” for my measurement attempt :wink:
In this case I don’t have a retaining ring so I will need to do it on the threads of the head.

The light in question is the Tool AA V2.0 Panda White, so the head architecture is different but I guess I will be able to do it! :+1:

Thank you once again for taking the time to explain :wink:

BTW, my initial uneducated thoughts were to remove the rubber cap and trying to put one each contact of the DMM on each side of the resistor !I guess it wouldn’t work well :smiley: :person_facepalming:

So, I tried the settings as NeutralFan showed above, but the data is approximate and not 100% accurate.
My Multimeter is AstroAI DM6000AR. Host is Tool AA panda white.
Driver is from a cheappo zoom flashlight. Lighted tailcap is from Convoy store, in orange.

First take:
Sanyo UR14500P at 3.79V
µA = 1737
mA = 2.30
A = 0.001

Second take:
Shockli IMR14500 (orange) at 4.12V
µA = 2434
mA = 3.28
A = 0.003


This was the second experience, with similar settings except for the lighted tailcap, which has blue leds.
First take:
Sanyo UR14500P at 3.79V
µA = 4285
mA = 6.48
A = 0.008

Second take:
Shockli IMR14500 (orange) at 4.12V
µA = 5253
mA = 8.03
A = 0.020

Do these numbers make sense? I suppose that microamps would be the best reference here, or would it be microamps?

Thanks again for your help :beer:

Even if those measurements are not exact and they’re just approximate, they’re still way too high. Once your in the milliamp range the battery isn’t going to last long. For reference, a good parasitic drain should be between 20 and 100 microamps. 200 to 300 is not that bad, but as the numbers go up, the situation gets worse.

You might be able to reduce the drain by swapping leds or adding more resistance. If you have a clear tail cap button you can use a larger resistor. This one light I added a green led to had a 6400 µA draw. I swapped it to a blue one from a different company and the draw went to 1200 µA. Then I swapped the 5k resistor for a 24k and the draw went to 320 µA and was still decently bright. So it’s possible, just a lot of extra work.

PS, your meter seems to be reading strangely because 1000 µA = 1 mA. Your getting entirely different numbers as opposed to it just moving the decimal point.

I have two non-technical questions: Why is it so difficult to buy 26800 battery for flashlight? None on Ali Express and Banggood!

And can I use a 26700 cell instead of 26800 cell in a flashlight?

Thanks for the information and clarifying JasonWW! I also thought about that, it being too high, but I wasn’t able to try in another flashlight. I will do so tomorrow and verify if the numbers are still that high. The driver is cheap AF, and the lighted tailcap may be done for differente batteries (even if they would probably register those high numbers).

Hum, I guess I would not risk replacing the leds, I would damage them with my soldering skills before they went into place :stuck_out_tongue: Still, that would probably be the best solution. I will try to get some photos of the setting tomorrow and post it here for further information.

And I am also concerned about the DMM. I am not very skilled it it, nor do I know how to use it well, but I also thought something was wrong with those readings.
I’ll check in another flashlight tomorrow!

Thank you very much once again :+1:

Because virtually no flashlights or other products use that size. As more products start using it I’m sure more companies will start stocking it.

Sure. If there is no contact, you can solder a spacer to the spring to make it longer, swap in a longer spring or maybe just stretch the existing spring.

Thanks Jason WW for your response.

A follow-up question: If I use a 26700 cell instead of a 26800, will adding some small magnets on top of the 26700 cell help improve the contact?

It can work, but the danger factor is a bit high. Magnets can sometimes slip and make contact with the flashlight body. Like if you drop it, it could potentially cause a battery short. You might can add some glue to the magnets edge so it can’t slide, but I personally just stay away from using magnets.

I have an Aneng AN8008. Just recently got some fuse for measuring amps since it came with a blown fuse. Tried to measure a convoy S2+ and it shows the amps but it has a very audible buzzing to it. Not sure if this is a feature but I don’t see a mention about this in HKJ’s review. Is this common with DMMs?

If you had someone 3d print a spacer that has a hole in the middle you could put a piece of brass rod in the hole (or glue in the magnets).

That reminds me, you can buy a spacer.

https://m.aliexpress.com/item/32667378904.html?trace=wwwdetail2mobilesitedetail&spm=a2g0s.9042311.0.0.27424c4dqMasl2

Or

They might be a little too thin, though.