I love that design!
Back then I ordered some drivers from gchart, but those would be used with 3V LEDs, not these LEDs.
Sofirn made the C01 with 5mm Leds, using AAA batteries, with the same kind of purpose but with a different host.
Maybe this is helpful:
I believe they are currently sold out, though 
BTW, welcome to BLF 
Looks like the sort of light that would benefit from a joule thief circuit.
I looked into making something similar a while back with a blinking locator LED for marking tentpegs/guylines when car camping but ran into difficulties making a flashing circuit…
I’m not sure how reliable the connection would be. Does a light like this even need a switch?
Hi MascaratumB, thank you very for the info, yes those links r very helpful!
About the LED
The 1st reason I picked 5mm just because it come with lens, so no need for reflector I guess
(I do prefer COB because I’m going to use a heat plate to solder, so if every thing is SMD that will be easier)
The 2nd reason is to make it run for long hours, . I heard 5mms run longer than COB, but not sure.(I can not figer out the 5mm led’s watt per hour)
also if it could have good CRI that will be a plus.
On digikey the 5mm and COB are under different category, made it very difficult to compare. especially I am not very familiar with LED chips.
So the ideal LED is:
No need for reflector
24h run time on 1 AA（40mh 3v I guess?）
Good lumen per watt
Good CRI
Just want to ask if you have any suggestions about the LED chip? Thanks!
Hum, I would not be the best person to inform you about the driver for this flashlight.
As I mentioned, when I was looking for a “joule thief” flashlight (the link you posted above) I dealt with member @gchart and he built some adequate drivers for my need, although not for 5mm LEDs.
Maybe he can help you with that. Or maybe you can contact Sofirn ( @Barry0892 ) and check if they have some spare drivers from their C01 flashlights.
Otherwise, I am not aware of drivers being sold for those leds.
Maybe someone can give some more info on this? 
Similar to the ZXSC380 that was mentioned, the ZXLD381 is cheap and easy to implement. While not designed for a 5mm LED specifically, there’s no reason why you couldn’t solder one to the pads on this driver board. I have some testing details about that here. Heck, I think I still have some of these boards and components sitting around. If so, they wouldn’t take much time at all to build some up. And as simple as a design as this is, I could throw together a new driver that’s meant for a 5mm LED and a AA battery.
As far as some good 5mm LEDs go, you could try and find some Yuji’s or see if any of these are available.
BTW, neat concept with the 3D printed twist housing!
If you can get one, the L3 Illumination L10 is a good minimalist AA light. It’s about as small as an AA light can get, and runs AA cells down pretty low. Plus, it has a really nice beam and good runtime and a simple but effective interface… either low/med/high or moon/low/med/high, in that order. The low mode runs over 24h per charge, from what I recall, and is what I almost always use. It was built in both XP-G2 and Nichia 219B flavors, and I really like the 219B one.
But that’s no fun, because it already exists… you wouldn’t get to build it.
oh, sorry, when I say “LED chip”, I actually mean “LED emitter”.
I was trying to find some better LEDs, but seems 5mm is the best so far, everything else I can find will need lens/reflectors.
Hi gchart, thanks for the info! the post you linked are great, actually I saw them before I posted here. they are one of the reasons why I started this little project 
thanks for your informitive sharing again.
I just ordered some ZXLD381, 15uh inductor，and some 5mm leds. hopefuly everything can go together nicely.
Just wondering by any chance if you know the Sofirn C01’s drive setup? I couldn’t find it anywhere.
Thanks!
Oh I see! Sorry, I thought you were looking for the driver 
Well, but gchart has replied and mentioned the Yuji Leds, which are also used in the 2nd version of the C01.
I hope you find them and manage to build that flashlight! Seems a nice concept
I have a super lightweight plastic AA 2 mode w/ two 5 mm hi cri and a red 5 mm. Headlamp . It vampires all old alkalines . One of my favorite el cheapo lights only thing I’d change is I’d drop the red for a true two mode 1 led or 3 . Right now it runs at about 8 lumens on two 5mm Yujis . I’d like a second mode running one at about a lumen or less .
There is great joy in taking out the last of a cell known for trying to take out your electronics . Nothing will ever leak in something you use often . It’s when you put it in the drawer and forget it …
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“Best used by 2024”, it said…
Oddly enough, I’ve never had a cheap generic alkaline cell leak… it only ever seems to be the name-brand ones. Specifically, Duracell.
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you may be able to simplify your electrical design by using a module like this and a current limiting resistor for the LED: DC-DC 0.9-3V to 3.3V Step up Boost Converter Module 1V 1.5V 2V 3V Power Supply | eBay
I have some AAA made for Menards that are leaking in the package too …
with a 2028 expiration date
Yarrr, matey! Yer nards ain’t s’pose t’ leak! Stop puttin’ bat’ries in 'em!
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I tend to avoid alkaline.
In regular used devices like my goto digital multimeter I use NiMH. In the once a year DMMs I have 1.5V Lithiums.
They don’t leak, they work well in cold weather. Pricy, but IMHO worth for DMM or the emergency backup Lamp in the car. You buy a car fit it with a lamp and Li, when you sell the car the lamp still works.
Mostly from Energizer, but other brands will do
Energizer L91 is AA
Energizer L92 is AAA
The standard shelf life was 10 years, like CR123, now they are claiming 25 years
Someone gave me a bag of old CR123 cells a few months ago… so I put one in my Olight S-Mini Ti since it’s the only light I have which can use that cell type. And I’ve been using the light a lot.
On a 16340 cell, this light would typically last for about a month between charges. But with CR123, it has been like 4 months already. It really seems to pull all the juice out of these things!
For AA, I use up old cells with a L3 L10-219. For AAA, I use a DQG Tiny or an Old Lumens memorial light.
With all these CR123 cells though, and how long each one seems to last, it might take a very long time before I run out.
Dear Flying Spaghetti Monster 
From what i understand Alkaleaks leak when they are empty and stored that way. The ones that leak before being used have self drained. That said i agree that Duracells seem to be the worst offender, but i have seen all brands leak.
I have even seen NiMH leak, though its a lot less damage done. Except Eneloop, my luck has been good that i have never seen one leak yet. Or Ikea Ladda since i have not had any as old as the other brands, all mine are under 5-6 years old.
I prefer rechargeable batteries, except I still use 9V alkaline batteries in my smoke detectors.
I am curious if anyone has been satisfied after using the battery “no-leak guarantee” offered by Energizer:
Also, in the United States prior to 1996, many batteries contained mercury to prevent the buildup of internal gases that caused battery leaks: