The There Are No Stupid Questions Thread

I am already 3 weeks into an order from Convoy and was trying to get on in 2 weeks.
This is a feasible driver correct:

Yes, that should work fine.

The Convoy 4x18a flashlight sbt90.2 can be purchased with or without its 18650 batteries,
I don’t know anything about the included batteries, and I am wondering if it would be worthwhile to purchase them separately for a performance standpoint?

It looks like Convoy is offering 4 of the Liitokala 3500mah cells for an extra $18. I’m not too familiar with that particular cell and I can’t find any reviews or tests on it. All I can say is it would fall in the “high capacity” style which looks like it would be fine for this light. Does anyone know the driver type of the SBT90.2 version? If its a FET driver you might be able to squeeze out some more lumens, but only when measured. Its doubtful you would see the difference with your eyes.
Those included cells should be fine.

Thank you for taking the time to reply, I will be ordering one for me and two as gifts it will make things a lot easier!

OK - i have a stupid question!

I feel like i should be able to understand this by now, but every time i think i do i realize i dont.

Regarding XHP35, XHP50.2 (NOT 3 volt), and XHP70.2

-Are they all both 6volt and 12volt, depending on how the LED's mcpcb is made? Or are xhp35 and xhp70.2 12 volt, and xhp50 6 volt?

The reason i'm confused (i feel compelled to explain) - i have asked Simon @ Convoy numerous questions about putting a xhp35 in a xhp50 (6 volt) light he offers on his page, or about putting an xhp50 in a xhp70.2 light he offers on his page, or any one of the combinations you could think of between these three LED's and all the awesome offerings h has for them.

Sometimes he says yes it can be done, and sometimes he says no it cannot. Just today he told me the xhp35 could not be put into the M3c-u light he has because there is only a driver for xhp70.2 so far. What does that mean? if they are the same voltage, would there be another reason they wouldn't be compatible? Could the amperage be too high for the xhp35?

Also, based off of Simon and my conversations, i was sure i knew that the xhp70.2 was a 12v LED< but then looking on his AliX store today ( i do this often) i found the LED offering for a "xhp70.2 6volt on 25mm mcpcb".

So now i am lost.

NOTE: * I am NOT blaming Simon for my confusion. I feel like if i actually spoke face to face with someone who knows this information, i would've understood it months ago, but sometimes with the "back and forth" of the computer, key info gets lost to my brain. thats a "me problem".

What volts are these LED's? Or is the voltage for these particular LED's determined by the mcpcb layout? (i feel like once u/cncman shared pictures with me of 12volt mcpcb's vs 6v mcpcb's.

Thanks!

The XHP35 is 12v only. I know the XHP70.2 can be 6v or 12v (depending on MCPCB) , and I’m not sure for the 50.

Page 28 of the XHP70.2’s datasheet ( https://cree-led.com/media/documents/ds-XHP702.pdf ) show this image of the bottom pad where you can see that the outside pads are split to allow for more than one configuration. This allows the XHP70.2 and the XHP50.2 to be configured as either 6v or 12v.

Page 35 of the XHP35.2’s datasheet ( https://cree-led.com/media/documents/datasheet-XHP35-2.pdf ) has the following image which shows that the same pads are solid which means it is a single configuration only, in this case 12v:

You’re right, the answer doesn’t specify why the driver would work with the 70 and not the 35 as it’s possible for a driver to work with both.

thank you!

Wow, thank you for this in depth look Marc E! I really appreciate it, this helps a lot. I have looked to the data sheets to find this information before, but admittedly never went to the "back end" of them (P.28) and looked, thats why i probably never found the information i was looking for. although if i did see the items you shared, i probably wouldn't of understood what they are depicting anyway, without an explanation like you provided. So, thank you very much!

It seems you have this figured out now. I’ll add a little bit more.

In order for the xhp35 to be tightly packed, Cree actually joined the edges of the core in such a way that there are no wires connecting them. See below.

This gives them virtually no gaps between the cores and you get a better result (tighter beam, less artifacts). There are only 2 electrical contacts on the rear.

The xhp50 and 70, on the other hand, have the cores separated. The 50.2 and 70.2 have the same gaps, but the yellow phosphor is just spread all over minimizing the gap appearance.

It’s cores are wired such that 2 of the cores are in series and the other 2 cores are in series. You then have 4 connectors on the back. The MCPCB is what determines if it will be 6v or 12v. It can connect the 2 series cores in parallel for 6v or it can connect the 2 series cores in series and you get 12v.

The newer 3v version of the XHP50.2 has the cores internally wired all in parallel and only have 2 electrical connections on back. This is why it’s 3v only.

Keep in mind that these 4 core leds (xhp50 and 70) are basically just 4 smaller 3v leds combined. You can see the combinations in the second picture I posted.

Thanks "JasonWW" and others for your explanations and to those who ask interesting questions.

The discussion and diagrams clarified LED characteristics that previously confused me and understanding them makes this hobby more interesting.

Thank you Jason for your enlightening posting!

Wow, that's awesome info Jasonww, thanks for all that info. I appreciate it. Never realized the 50 & 70 were just a combo of 4 smaller leds!

You guys like that, huh?

Here’s a couple more pics showing more detail on the Cree Xtreme High Performance leds. This is a 50.2 below. The 70.2 is similar. Both are 2nd generation.

Ignore the tiny wires cut above and missing below. They don’t flow the main current. They are something to do with anti-static or something. I can’t remember off hand. The led still functions with the tiny wires cut. (The true positive and negative may need to be swapped around in the image above. I chose them arbitrarily for demonstration purposes since I could not see the mark on the backside.)

Now the 1st generation xhp50 and 70 had positive and negative lead wires coming out of each core. I added some black marks next to the leads since they are difficult to see. (Please excuse the low-quality image)

Here is a 5050 MCPCB that can be used in 6v or 12v.

In stock form it is not passing any current. If you want it to be 6v you would add some solder to the pads where the blue arrows are pointing.

If you want it to be 12v you would add a solder bridge across the yellow arrow pad.

All leds have some indicator on the top or bottom to show polarity to make sure you solder it correctly onto the MCPCB.

(The original pics are not mine, I found them online a long time ago. The MCPCB pic was outlined by the someone else, also.)

I have one question which requires experts to advise: Which metal flashlights incur high risk of lightning when outdoor during a thunder storm?

From own assumption: copper is the worst, followed by brass, stainless steel; aluminium should be quite safe, and the least dangerous metal is titanium. But I am not sure about my assumption.

I guess it is just common sense not to bring out any metal flashlights during a thunder storm, and to hide them inside our backpack if we are hiking in the open.

I don’t know if your joking or serious.

Jason WW, I am serious. Really want to know.

I just note that many flashlights are made of titanium, copper and brass. In fact I have just bought two Astrolux FT03 Mini brass and copper flashlights. I think they should not be used outdoor when it is raining.

But what about the common aluminium flashlights, and those made of titanium, which I assume are not attracting lightning much. Please correct me if I am wrong.

Just avoid ones with magnets in them, like in the tailcap. That will suck lightning to you like fat kids to a candybar.

It should not be an issue. Unless your holding a metal rod well above your head in an open area, I don’t see how holding a flashlight would have any effect as far as drawing a bolt of lightning towards you. Just my opinion.