5V Power question: I make costumes so I need a SMALL power pack. I have been using LiPo batteries from Adafruit but they provide just 3.7v and I’m running into power issues using the Trinket Pro 5v or the Beetle board. Does anyone know of a small, simple battery solution that will give me a clean 5V? (using 4 rechargeable AAAs is just … bulky and awkward). Thanks!
I’ve used one of these before: http://www.jackeryusa.com/#!jackery-bar/c6ce
Rated at 2.1 amp output @ 5v
that looks promising. No specs on how big it is though… 
Adafruit now carries a combined lipo charger + 5V boost unit: https://www.adafruit.com/products/1944
Or just the boost if you don’t need a built-in charger: https://www.adafruit.com/products/1903
Mine was approx 4"tall x 2" wide x .75" thick. I was able to extract the guts and make it even smaller.
2600mah usb rechargeable battery.
Oh that adatfruit one is tiny though
I’m testing a regulator from Auracomms tomorrow, that way I can use a 7.2V race pack from a remote control car, step it down to regulated 5V at 5A, will let you know how it goes
If you don’t need more than 2A, I’d go for one of the “lipstick” external phone batteries. Check the specs though—the cheap ones probably won’t live up to theirs.
Why not just put 2 of the Adafruit Lipos in series to get 7.4v then use a 5v Step Down board. And if you want extra capacity (Lights on for longer) then you can add 2 more in parallel.
I just bought a bunch of differently-sized “phone recharger” packs with USB outputs, to see what they’re capable of. If they work I’ll probably just use them exclusively for small projects in the future.
I use 2S lipo packs with buck converters to step down to 5V. The buck converters cost about… a buck. 
Maybe $2 for a US-made one.
Something to consider
I built many led customs before
And using a regulator will
Drive a problem of heating that
You will need to solve in order
To make the custom comfort
Pro tip: don’t wire the USB outputs of external battery packs together in parallel. You will burn out their boost converters. This gets expensive quickly.
Ask Me How I Know™.
@Robert_Atkins Did you experiment with any power banks that do live up to their specs? I’m thinking of using them for <2A projects
Well, I’ve used the LimeFuel L130x on my current project, and after I stopped tying their outputs together in parallel (which I was warned wouldn’t work) I seem to get reasonable results. You can go two ways I guess: buy name branded stuff and kvetch to the manufacturer if they don’t work, or buy cheap Chinesium in bulk and replace them when they die.
I’ve only used cheap usb rechargeable batteries as Roberts mentioned. I never tested the Amps… but ive only had good success running 150 leds off them with no problems for 4-6 hours. I end up cutting the brightness to 50% because its too bright.
@elad_o I use XM1584-based buck converters - they are tiny and very efficient and don’t seem to generate much heat at all. The wider the differential between voltages could be the issue - I use 2S lipos - 7.5V at full charge, down to an operating voltage of 5V isn’t much of a step-down. YMMV
I havent had any luck with using 5v step ups from li-ion’s everyone i use stop working when i add LED’s i can power a micro but not with LED’s hooked up no matter how i wire them. I have tried about 3-5 different ones with same results. I do have a rather large unit from pololu #2565 that may work but was to larger for my application.
I’m stepping down, not up. Use 2S lipos.