Are my estimations correct? (parasitic drain in different lights)

LED Flashlights – General Info
1

Since 2 days ago, and due to this thread (Skilhunt M150 Lock-Out Function Current Draw?), I started thinking about some lights I have and started “testing” them. What they have in common is that all are e-switch flashlights.

The lights in question are: Skilhunt M150, Skilhunt M200 and On The Road M3 Pro.

Both Skilhunt lights have the possibility to do electronic lock-out and to enable the switch blinking red, as a way to find them in the dark. This possibility can be enabled or disabled. The OTR M3 Pro doesn’t have electronic lock-out.

I did a simple “test”:

  • In the Skilhunt flashlights, I measured the battery voltage, put the battery into the lights, locked them with the blinking switch enabled and after some hours, I took the battery out, measured the battery voltage again. After this, I put the battery into the lights again, locked them without the blinking switch enabled and after some hours, I checked the batteries again.

- In the OTR M3 Pro, I just measured battery voltage, put the battery on the light and after some hours I checked the battery voltage again.

- During these periods, I didn’t turn the flashlights ON, and the only light that appeared was because the Skilhunts turn the light ON while being locked out.

What I got:
Skilhunt M150 (with blinking switch enabled)
Starting voltage = 3.68V
Voltage after 6 hours = 3.65V
Drain: 0.03V in 6h

Skilhunt M150 (with blinking switch disabled)
Starting voltage = 3.65V
Voltage after 10 hours = 3.65V
Drain: 0.00V

Skilhunt M200 (with blinking switch enabled)
Starting voltage = 3.81V
Voltage after 13 hours = 3.79V
Drain: 0.02V in 13h

Skilhunt M200 (with blinking switch disabled)
Starting voltage = 3.79V
Voltage after 10 hours = 3.79V
Drain: 0.00V in 10h

On the Road M3 Pro
Starting voltage = 4.11V
Voltage after 7 hours = 4.06V
Drain: 0.05V in 7h

Even if this is not “super scientific measured” data, are my estimations (BELOW) correct about the potential draining from 4.20V to 2.80 (=1.4V) ?
I did a “Rule of 3” calculation.

Skilhunt M150 (with blinking switch enabled)
In this light, a battery would be drained from 4.2V to 2.8V in around 11.6 days
[0.03V drained in 6h; so 1.4V would drain in 280h. 280h = 11.66 days]

Skilhunt M200 (with blinking switch enabled)
In this light, a battery would be drained from 4.2V to 2.8V in around 37.9 days
[0.02V drained in 13h; so 1.4V would drain in 910h. 910h = 37.916 days]

On the Road M3 Pro
In this light, a battery would be drained from 4.2V to 2.8V in around 8.1 days
[0.05V drained in 7h; so 1.4V would drain in 196h. 196h = 8.16 days]

Why am I doing this?
To inform manufacturers about this type of drain in these e-switch lights, and to lead them to make this information public for customers.
I may, of course, have “faulty” flashlights and these may be abnormal drains, but I guess people should know about this when buying their lights.

Also, there is a great possibility to drain the batteries down to 0V, which is even worse than just draining to 2.8V…

So, help me on this “exercise” and share your data if you have them.

And please comment on how “good” or “bad” are these draining values.

Thanks in advance :+1:

2

Most of my lights I lock them out either by unscrewing the tailcap, or the head. Tailcap does not always lock out.

3

Voltage vs capacity is pretty nonlinear, and even varies by type of cell. Best to go by current, and extrapolate.

Eg, a 1mA drain would be 2400H for a fully-charged 2400mAH cell. So 2400/24 would be 100days, around 3mos.

A 10mA drain (eg, light with magnetic ring/slider) would have only 10days before draining it dry. Etc.

4

Well, I believe these lights also lock physically (although I suspect the OTR M3 Pro doesn’t have stop the drain - I may have a faulty light).

However, the question here is not what is “practical” or not for us users, but the “design” of the lights and what they may imply for people that are not always looking to these details and that may “run out of juice” in the middle or nowhere while expecting the lights to have battery.
That is my major concern (along with the potential drain that it takes for the batteries if they go down to 0V).

Ok I think I got some of this, but maybe not all, so bear with me.

I know I am dealing with many variables here, but if I use other batteries and the light behaves the same way (same drain), doesn’t it imply that the flashlight will stop working properly when flashlight reads “2.8V” or less (or the cut-off voltage it works with)?

That’s what I’m “worried” about and the measurements above are just an exercise. Maybe manufacturers can decrease the drain.
I now that the calculation you did is more reliable though.

(I’m sleepy so all of this can make no sense… :person_facepalming: )

5

Someone (HJK?) posted graphs of various makes of cells and capacity vs voltage. Some cells peter out at 3.4V and drop like a rock suddenly (ie, are already near 0% at that higher voltage), while others have a gradual taper down to 2.8V or whatever and still have plenty of juice left at 3.4V.

Best it to just get the capacity of the cell and measure current draw of the light.

6

Yup, LB. It was HKJ: Battery charge percent

MascaratumB, like LB was saying originally, it is best to measure this using a DMM if possible. I have one capable of measuring “uA” while most of the rest can at least measure “mA”. Essentially you remove the tailcap, put the DMM in uA or mA mode, and put the leads in between the battery and the body (replacing the path of the tailcap). This will tell you the rate of drain.

Many times if something active is happening (like a blink) the MCU may be left running at normal speed instead of sleeping. This can have a very high drain. Like 10mA vs 5uA (0.005mA).

7

Ok, now I got it! Like I said, yesterday I was sleepy and my brain was not doing the right connections!
So, the drain may not be linear, then the estimated time to drain the battery can be over or underestimated.
Thanks LB :wink:

Thanks gchart! I tried with my Uni-T UT33D multimeter but I guess it doesn’t read such small values. I need to get a decent one or a DMM to make this type of measurement!

Also, as I am not familiar with some of these measurements and concepts (theoretically and empirically) I was relying more on the type of “action/tests” i did above.

Now I see they may not be worth due to the aspects you guys mentioned :wink:
Thanks again for the clarification!! :+1:

8

I’m not sure, but it looks like your model does measure mico amps. It’s marked 2000u at about 7’oclock on the selector dail.
That should be plenty good enough for parasitic drain measurements.

9

Please see if I am doing something wrong in the images below.
I am trying to measure on a Skilhunt M150 and on a Sofirn SF14.

10

You might give the next setting or two a try (20mA or 200mA). The 2000uA setting is max 2mA. The lights might be max’ing that out. Especially the SF14 being a clicky, the flashlight will try turning on and will likely be using more than 2mA.

Even the M150 will probably be over 2mA. The MCU will try turning on and unless they’re using a really low power mode, it’ll initially be quite a bit over 2mA.

11

Just tried what you mentioned with 4 different lights (Skilhunt M150 and M200, OTR M3 Pro, and Sofirn SF14).
I tried all 4 on the three settings (2000, 200 and 20) and the results are always “Zeros” :zipper_mouth_face:

I guess the multimeter is damaged :zipper_mouth_face:
I went to look for an older post I did and it was working… not now .

So I will not have results with this :frowning: and this function is ruined…

Thanks again for your support on this and for your explanations!!!

12

It may be that the current probe fuse has blown on your meter. Easy to do this accidentally by trying to measure something that exceeds the rating (200mA in your case).

Try the 10A probe hole for the positive lead and the 10A setting on the dial, then reduce the setting one step at a time to see the reading.

13

That’s probably what happened :zipper_mouth_face: And…it is probably not an easy fix, is it? :weary:

I tried what you suggested, but only zeros again. It was the fuse, most probably.
Thanks for the suggestion!

14

I think you have to switch the red+ probe lead to the Amp side, far left hole. :+1:
Alot of meters have this same feature.

15

The fuse should be an easy fix if you have a spare fuse—sometimes there is a spare in the case. You will have to open the cover, likely some screws on the back cover to access the battery and fuses.

16

I tried it on both, middle and left, and on the different settings above. Nothing works… Sometimes the - appears, but it disappears then…
I believe it is “poof” :person_facepalming:

17

Then like others have said it’s about got to be the fuse.
You can just jump the fuse to get it working but I wouldn’t try to actually measure current draw with the light full on unprotected like that.
Even a lesser value fuse would work for measuring the parasitic drain.
The red probe lead will have to be in the left side hole though.

18

Given the current situation I may have to wait some weeks to take it to the store where I bought it and check if they have fuses there. It is a small shop, but the guy seems savy on this.

Stupid fuse … or stupid me :rage:
Now I won’t be able to entertain myself measuring this :person_facepalming:

Thanks for the help folks :+1:

19

Two screws and the rest is up to you.

20

Take a 9V battery and hold one lead, touch the other lead to one nipple (on the battery, duh), then touch the other nipple with your opposite hand. Ie, use yourself as a resistor. See how much current flows through the meter. You can throttle it by squeezing harder on the leads and lightening up, too.

The SF14 is a tail-clicky, no? So making any connection is essentially turning it on, full blast. The fuse won’t blow, but it’d show overrange “0L” or similar.

The sense resistance at the lowest scale might be too high to even let it get started, dunno.

So… first check the ammeter through a large resistance (multimeg). The “10A” socket is only used at the 10A range, and is unfused. That can make your meter go pouf, but V/Ω/mA should be fused.