The There Are No Stupid Questions Thread

Thanks so much.

These batteries are expensive, and flashlights that use them tend to be not much smaller than AAA lights, which offer much more brightness and runtime, IMHO. :)

We seem to be getting confused between “cell with button top” and “button cell”. They’re two different things.

“Cell with button top” on the right, “cell with flat top” on the left:

[Image courtesy of wheniwake on Planet of the Vapes ]

“Button cells”, also known as “coin cells”:

[Image courtesy of Wikipedia ]

I think you have that reversed. I have only one 18650/26650 light that requires button-tops (BLF Q8). All others either require flat tops (such as Zebralights), or work fine with flat tops (anything with springs or posts at the positive end).

Yes, I meant those coin cells. ;)

:smiley:

I don’t have the tools to test this. If I hook up a Nichia 219c 4000K directly (no driver) to a fully charged 30Q just to test and compare tints, approximately how many mA is it pulling?

The 219C has a low forward voltage (Vf), so unless the led has very good heatsinking, the answer will be too many, enough to damage it.

I agree with ggf31416, you’d definitely be risking damage to the LED.

You could just solder a 7135 or two to a piece of stripboard, though - that would be enough of a “driver” to keep things under control.

Question about Nichia. On Reddit I often read about this. Why Nichia so cool?

They’re one of the few LED mfrs that make high-CRI LEDs.

If you notice how if you’d use a CW (cool-white, ie, bluish-white) LED when looking at, say, a woodgrain cabinet, it’ll look a dull dingy grayish-brown color. With even low-CRI warm-white, reds and browns will “pop” and be much more vibrant.

High-CRI means that whatever color-temperature you’d have — cool, warm, or neutral — you’d be able to see truer colors as if under natural daylight, that blues will look blue, reds will look red, etc. Differences can be very subtle, and you’ll hear things like “R9 value” and such, which is a shade of red that lots of LEDs have problems handling.

Nichias were (probably?) the first to offer high-CRI LEDs, ’though now others are starting.

Thank you!
And what about Cree?
Why the majority of companies use Cree, not Nichia?
That’s too expensive?

$$

The Cree leds tend to be the leds with best output and efficiency. But the last two years some other manufacturers have catched up on both and usually do that with better tint/CRI/tintshift than Cree, so using Cree leds makes somewhat less sense atm. Some types of led however are simply not available other than from Cree, i.e. the XHP70.2 is big, cheap, efficient and has immense output, there is little competition for that.

That sounds really interesting. I read more about Nichia. In this week I understand, that I truly in love with Nichia:) I hear that Zebralight use N. in their lights.
What about other manufacturers, they produced their light on Nichia?

So, I have 3 stupid questions (or simple ignorance) about LEDs!

1) does a XPL-HI CW (6500K) have that annoying yellow core when reflected on a white wall? I am using both XPL-HI (+–5000K) and XPL-HI NW/CW (maybe between 4000-4500K) and both have that yellowish core either on SMO or OP reflector.

2) dedoming an XP-L2 (maybe 5500-6000K), that produces an annoying green shift, will improve the beam erasing the shift or will it make it worse?

3) I am planning to mod a 14500 flashlight with a MTN 17mm DD driver with guppy3drv. I would like to mod it with a NW Led (4500-5000K) that is powerfull (for small turbo boosts) but that, at the same time, does not produce significant tint shifts. What would be the best LED for that?

Thanks in advance !!!

3) Luxeon V or Samsung LH351D

2) XP-L2 can be sliced but not dedomed. I do not know results of slicing the XP-L2.

1) I have no definite knowledge about that. I have had a bunch of flashlight modded 7A XP-L hi leds and some leds produce the yellow center, some do not, it is not related to host, type of reflector, or focussing of the led and no diffrrence can be seen when looking at the led, wether off or lighted. It is still a mystery to me.

Edited / removed.
I think I succeeded in asking a stupid question. :smiley:

djozz, thanks do much for the answers :slight_smile: All clarified my doubts!
Funny thing, I’ve been using the Luxeon V but didn’t thought it was one of the best on the specs I wanted!!

About the XPL-HI 7A, I guess I will order some from Convoy and check how they behave. I wanna try them on OP reflector not SMO, so let’s see if some stay still and do not produce that yellow “stain”!

Again, thanks for all the answer and the correction about “slicing” vs “dedoming” :wink:

I have one question: will strong magnets be harmful to li-ion batteries if they are stuck together for long term?