The There Are No Stupid Questions Thread

Yes, no problem.

Ok thanks! (again)

I recently purchased a BLF X5/X6 driver from Banggood, and it produces a bright flash when switching to low, even from off. Do they all do that?

My turn!

1) Can you DD an XHP70.2 with 3S/9V?

2) Driver recommendations for a max-effort Trustfire TR-J19 - running 3x XHP70.2 P2 1A (likely 2S/6V)?

I have a TR-J19 which can run either 32650 2S or 3S, with a really bad driver in it. It’s been collecting dust since I bought it, and I want to update it. It’s massively heavy so it can take a lot of heat.

Many different drivers do that and the electronics experts have a good explanation for the phenomenon. There are design options for drivers that prevent it. That is all I know.

Thanks djozz. I had hoped there might have been something like a firmware fix - three more of the drivers arrived this morning! :person_facepalming:

There may be a firmware fix, anyone?

I keep reading that a light can be locked out by unscrewing the tailcap slightly because the threads are anodized.

I understand that the cell circuit for the flashlight is completed when the tailcap is fully tightened, thereby making electrical contact with the un-anodized end of the tube and un-anodized retaining ring (or whatever) of the inner tailcap.

This implies that anodization is an insulator?

If that's the case, how durable is the anodization?

That is, how much wear can anodized threads tolerate before the anodization wears away to the point that continuity is created just through the worn threads?

How rapidly does the wear progress on properly lubed threads?

This has been discussed a while ago. If I recall right the cause might be the FETs gate still loaded after disconnecting the cell with a short tap. If this is true a hardware modification is required to solve the issue - which has been done in newer BLF driver designs.


If you unscrew the tailcap often the anodization may wear off pretty fast, depending on its quality. I’ve seen this with my Q8 lights already. Grease helps of course.

The anodisation is quite hard it has Mohs hardness of 9, 10 would be diamond. And you can have different thicknesses of it
With lube it should last therefore years.

Hi all new guy here and my stupid question is what does 2SPS mean/stand for?

“Hi all new guy here and my stupid question is what does 2SPS mean/stand for?”
2S2P means 2 serial, 2 parallel, like this:

4S1P is 4 serial, 1 parallel, like this:

2SPS isn’t a thing in battery circuitry.

Thank you

Thanks joechina.

Are illuminated tail caps always ON?
Will a light with a twisting tailcap lockout turn the tail led on/off?


A lighted tailcap is on when the flashlight is off. As soon as you turn the flashlight on, the LEDs in the tailcap turn off. When you twist the flashlight tail out, the lighted tailcap turns off, and accordingly the flashlight can no longer turn on. The lighted tailcap is on the same circuit as the flashlight.

That’s what I thought/figured.
Thanks for answering.

If I want to eliminate a thermistor, can I just connect the wires going to each end and bypass it with no resistance? I’m switching leds in my TM16GT from XPL HI to XHP35 HI. Not sure if eliminating the thermistor is such a good idea, but want to keep my options open. Since I’m going from a quad MCPCB to 4 individuals, I’d have to find a way to mount the thermistor. I could probably file down an old XPE star and mount it on there, then glue it down.