Q8, PMS SEND TO THOSE WITH ISSUES BLF soda can light

Neko2 · January 30, 2020, 1:40pm

JasonWW:

Oh wait, I see your earlier post where they did work, but now they don’t. I’m guessing they got drained while in the light. This should definitely not happen unless you have a defective driver.

What you need to do is measure the parasitic drain on your light. You do need at least one proper battery to do it so this may have to wait till you get one, but here is the whole procedure.

Basically you can use one cell and hold it on the head like this similar light.

You keep your test leads in their current meter spots which is COM and V Ω mA.

Then set the dial to the green DCA section 200m. Apply the test leads to connect the ground side, but leave the flashlight off. The light should blink twice, then wait about 5 seconds and it will go to sleep mode. Then you can get a reading. Assuming it’s not overloaded, you can switch the dial to the next 20m then 2000μ and then 200μ. Normally this light measures about 30μ when asleep which is super low amperage. Since you might have a big drain, we start at the higher 200m setting and work our way down.

It’s pretty rare for these lights to have a big drain, but they do happen from time to time. If both your lights check out fine, you might have had one bad battery which was self discharging. Since they are all in parallel, one bad cell could pull the other three down. This is also pretty rare. 30Q are very high quality cells. Still, something happened and we need to find the source of the problem.

I have a flat top Samsung 26FM and since I’m holding it in place, thought it would work for the test.
I get –08.7 on the 200m setting on my old light and –05.6 on the new one.

JasonWW · January 30, 2020, 1:45pm

Why risk ruining 4 new cells? It’s pretty easy to measure parasitic drain. Then you know if there’s a problem or not.

I wonder if the person sold it because they knew it had a drain problem? Maybe. If the driver is bad, you can get another for $10. To swap drivers requires soldering 5 wires.

If you can’t solder, well, another option to “fix” it is to just twist the battery tube when your done using the light. This cuts all power. It won’t drain at all. This is the best way to store a light.

Neko2 · January 30, 2020, 2:05pm

I posted the drain I’m seeing on both lights 1 post up.

JasonWW · January 30, 2020, 2:12pm

I think your not waiting the 5 seconds for the reading to change. On my light I initially see 5.2mA (milliamp), but then it drops to 0.11mA.

Just a note, I said the parasitic drain should be about 30μA (microamp). I was going from memory and that is with the green light turned off. With the green light turned on it’s about 130μA (0.13mA).

Neko2 · January 30, 2020, 2:23pm

With the green light on, it starts at –08.7 then drops to –03.6 after the 5 seconds.
Both are over reading for the μA settings.

To make sure I’m doing this right, should I have the black on the inner threads or the outer ring of the driver?

JasonWW · January 30, 2020, 3:07pm

Neko2:

JasonWW:

Neko2:

I have a flat top Samsung 26FM and since I’m holding it in place, thought it would work for the test.
I get –08.7 on the 200m setting on my old light and –05.6 on the new one.

I think your not waiting the 5 seconds for the reading to change. On my light I initially see 5.2mA (milliamp), but then it drops to 0.11mA.

Just a note, I said the parasitic drain should be about 30μA (microamp). I was going from memory and that is with the green light turned off. With the green light turned on it’s about 130μA (0.13mA).

With the green light on, it starts at –08.7 then drops to –03.6 after the 5 seconds.
Both are over reading for the μA settings.

To make sure I’m doing this right, should I have the black on the inner threads or the outer ring of the driver?

Usually the test probe polarity doesn’t matter for current, but if you see a negative number, just switch the leads around. It should read the same just without the minus sign. Oops, I misunderstood. Pressing against the outer driver ring is best.

So the 8.7mA drops to only 3.6mA after 5 seconds? That’s 30 times too high. Let’s see, with 4 x 3,000mah cells that’s 12,000mah ÷ 3.6mA is 3,333 hours or 138 days for it to go from 4.2v down to about 2.8v or so. Let’s say you were pretty low on power when you last used it, say 3.2v. About 30 days doesn’t seem like enough time to drain it to below 2.5v. Especially since the parasitic drain tends to drop a bit as the voltage drops. Weird, I might be off in my numbers, though. Also, the drain might vary based on what’s causing it. It might have been worse before you checked it over. Stuff like filtering capacitors can short or 7135 chips can leak. Who knows? You’d really have to trace the current leak to find the problem.

Did you check the new light?

Neko2 · January 30, 2020, 3:29pm

It appears to ramp down. It goes from 5.6mA to 118μA after the 5 sec.

I double checked the old one and it doesn’t ramp down any further.

JasonWW · January 30, 2020, 3:44pm

Okay, that’s good. That’s what it’s supposed to be.

So something on that first lights driver is bad. With a decently powerful soldering iron you can swap drivers. Maybe you know someone who solders?

Or else just always twist the battery tube after your done using it.

Here’s the link to the driver if you are interested.

#Aliexpress US $9.52 | BLF Q8 Driver Chip Q8 Circuit Board

Neko2 · January 30, 2020, 4:12pm

Awesome, thanks!

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kwcha333 · July 29, 2020, 3:44pm

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