Portable Power Sources
I have been using a RC style rechargeable Lithium Polymer 11.1v 5000mAh 56Wh 25C battery pack. I am loving it because when I first stumbled into this FastSPI realm, my only strips are UCS1903’s that run 12v and pull 3 amps per 5 meters at full brightness (this is the specs from the manufacturer). According to my research, 25C means that I can pull up to 90 amps of continuous power from this battery pack? I hope someone can confirm this, I am new into electronic engineering. That explains why I can run my led fx stuff for hours while I debug or write new code. On just one strip at half master brightness, I was easily getting 7-8 hours off a single charge.
For my test rig (an Adafruit Arduino Micro with a few pots and buttons) I have created a 10 x 9 matrix from almost 10 meters of strips wired in a “reverse S” (is there a better way to state “that”?) and I power the strips from both ends with the battery pack. I am very happy with the performance and wanted to discuss the topic of LiPo batteries. I paid about $60 from a local hobby store for mine. With my 3 amp charger, it charges in just over an hour on a 11.2v total remaining charge.
LiPo batteries are potentially very dangerous. You never want to short one of these things as they may/will catch fire. This concerns me when I think about attaching LED rigs to my, or someone else’s, body. Am I over paranoid regarding this?
They do require a bit of maintenance if you don’t get a pack with a low voltage cutoff circuit. I had to purchase a small voltage monitor that plugs into the balancing JST connector on the battery to make sure that I don’t discharge below 3.2v per cell. The little monitor scans and displays each cells voltage and the total battery voltage. I know that I want to expand into the realm of using the Arduino to monitor the voltage for me, but I am so consumed into just figuring this programming with Fast_SPI thing out, that that project may have to wait on the back burner till next year.
What do you use to power your portable LED projects?
Would “gerbils in a running wheel” be a valid answer? 
(I use LiPo and Li-Ion batteries.)
What about super-capacitors?
Never played with those on account they scare the crap out of me.
The 25C is the discharge rating, and is related to the capacity(mAh) of the battery.
The basic formula for discharge rating is (capacity in amps) * (discharge rating) = Amperage Draw. So for your battery, it would be (5Ah * 25C) = 125Amps. So you could ideally run about 200M of your particular LED strip off the battery without damaging it. Although, you could only do that for just over 2 minutes before you drained the battery to a point where the voltage would drop off considerably. The battery would also get incredibly hot as well.
That said, this has nothing to do with how long you can actually run your LED’s off of that battery. That is pretty much only related to the Capacity and your current draw. The battery capacity is 5000mAh or 5 amp hours, so a draw of 5A would take 1 hour to drain the battery. With your strand of LED’s at 3A (I will ignore the slight voltage difference of 11.v to 12v) You could run the strip for about 1.5 hours at full brightness. You likely are not actually running your LEDs at 100% white, and I usually assume that a rainbow pattern at full brightness is my biggest current draw, and still only draws about 50-70% of the maximum. This would give you a minimum of about 2-3 hours, and likely more time on a single charge.
Edit: fixed 5000mAh = 5Ah
LiPo batteries are rated per cell. A charged cell will show about 4.2 volts and the nominal voltage is 3.7. In RC the number of cells is the S so if you have 3S battery you have three cells in series and the nominal voltage is 11.1 and at full charge will have about 12.6v.
LiPo batteries also have a maximum safe discharge rate. That rating is expressed in terms of C which is the batteries rated amp hour capacity. So a 2200 mAh battery rated at 25C will let you safely pull 55 amps. Typically these batteries also have a peak C value. Exceeding the batteries discharge rating will cause the battery to heat up and the prismatic pack will swell. (if this happens set the battery in a safe place away from people and watch it for at least 20 minutes before moving the battery inside or packing it in your car.) Google Search LIPO battery fires for details - most of the stories are from years ago and batteries are much safer now. Safer only.
My best batteries are rated 5000mAh 4S at 65C sustained with burst capacity of 130C. So I can safely pull 325A with bursts of up to 650A at 16.8 volts.
A typical LiPo should be charged no faster than 1C. Read the manufacturers instructions before even thinking about exceeding the 1C charge rule. Faster charging can kill a battery.
I bought the higher C rating batteries because the max charge rate also went up. I can safely charge these batteries up to 8C or 40A (my best charger is limited to 20 amps) which cuts down the charge time.
A great source for LiPo and some Arduino clones is http://www.hobbyking.com. Be prepared to wait for shipping. And ordering from the International Warehouse can take as long as AliExpress via China Post.
Just a sideways comment here: I am intrigued by the LiFePO4 (aka LiFe) batteries. They have the lightness and of a lithium battery, and the casual no-fire, no-explosion charge / discharge characteristics of an old school lead acid battery. In fact, many LiFe batteries are sold as drop-in replacements for lead acid batteries.
On the downside, the have somewhat lower energy density than other lithium batteries. I’m not sure they’re ideal for walking sticks, but if you’re building a solar rig for the playa, “half the weight of a lead acid battery” might be a good selling point.
Anyone here used them yet? They’re new-ish.
I use a 2000mAh 2S 2P LiFePO4 15C battery in my RC transmitter. 2S 2P is a total of four cells two banks wired in parallel then the banks are wired in series for 6.4v. The nominal voltage of these cells is 3.2v. Fully charged the pack provides 7.2v but the peak voltage is very short lived and the pack provides 6.4v pretty much until empty. LiFePO4 have (depending on the source) about 15% lower energy density when compared to other Lithium chemistry batteries. From what I have read - LiFePO4 batteries are unlikely to have the same thermal runaway issues as other LiPo/LI-ion chemistry cells.
Thanks for the LiFePO4 battery notes.