It seem to be nearly impossible to solder such small contacts for the IC. I think It will be very hard.
I agree, those contacts are super small. I’ll be reflowing it, but even then, I’m not sure if bridging will be an issue.
Just for fun, I put together an update of the v1.3 board, but using the WSON version of the IC instead of the tiny BGA version. Still really small pads, but it looks more manageable.
Wow, looks like you’ll need a sewing needle to apply the solder paste. I’d like to try it, just for the challenge. 
Looks good gchart. :+1:
Happy Dance!
My v1.3 boards showed up today and I put some together using the TPS610995 (YFF package, a tiny BGA). It works flawlessly on both NiMH and Li-Ion and seems to be really efficient, though I still need to run some final numbers (which I will share later). I tested it in both the Sofirn SF14 and the Tool AA. No bleeder resistor needed in either! Though I did notice that efficiency in the SF14 on NiMH without the bleeder was worse; it’s like the main driver was trying to operate alongside the tailcap, though the main LED fails to illuminate. Adding a bleeder put efficiency back where it should be. The Tool AA did not exhibit this behavior.
This YFF (BGA) package is tiny and was a pain to prep. Going forward, I think I’ll be using the DRV (WSON) package.
:+1: :+1: 
You did it, Awesome job gchart! :+1:
Wow!
Sweet! :sunglasses: :+1:
Thanks guys!
For a little perspective of size, here’s a couple between a 0805 LED and an XP-L HI.
Some rough math says efficiency is running about 80% with either chemistry.
:exclamation:
Wow! You reflow these in an oven or hot air by hand?
Impressive work sir.
Edit I see above you’re doing it on a hot plate, EXTRA impressive!
Sorry gchart, but I can’t see your pics. 
Weird. I use a public Google Drive folder. Maybe I should just start putting them up on my server.
IDK, but I can’t see them using my MacBook with Safari. Maybe others can.
I see them since the first day. WinX-PC
I can see them now on my computer. Your change worked gchart.
Bill of Materials for Booster Tail v1.3, v1.4, and v1.5
- Step-Up Regulator: TPS610995 (YFF pkg for v1.3, DRV pkg for v1.4 & v1.5)
- Inductor: 0603 2.2uH ~750mA (such as LQM18PN2R2MFRL)
- Capacitors: 2 of 0603 10uF 6.3V X5R or X7R (such as CL10B106MQ8NRNC)
:+1: Nice
And how about a linear/buck tail for multicell lights?
A linear should be pretty easy. And I think a buck would be similar to the Booster Tails, just with a buck IC. Not a bad idea; though my only buck light is a stock L2 that I haven’t got around to modding yet. I could try throwing one together if there’s a demand for it.
Yes, linear should be fairly easy, you just need to find one with a small package and low parasitic current. It was just an idea to get another model for the “gchart edition” tailcaps. I just had the idea.
(maybe with a small potentiometer to change the current flowing to the tail LEDs? 
)
It’s totally up to you if you want to do this.