Hey everyone, I’m interested in wearable LED installations and I’m trying to figure out power.
My initial research suggests that 6S 22.2V LiPo batteries hooked up to a 12-24 -> 5v voltage regulator are a reasonable blend of price / weight / power. I’m considering 22.2v battery packs because they seem to be nearly the same price as 11.1v or 7.4v battery packs but offer higher total power. For instance:
Assuming 85% efficiency on the voltage regulator, I’m expecting to get 30Ah at 5V. Thoughts on this? Is there a better solution?
I get the sense that the Ray Wu LEDs on Ali Express are a good blend of price vs. performance. Thoughts on these?
What sorts of real-world power consumption numbers are people seeing? I know it depends on my designs and intended brightness… is there a rough factor you like to use when brainstorming power supplies for your LED wearables?
Ive personally had great success with rechargeable USB batteries. Both 2600 and 5200mah sizes. I ran my LED stickman (4m of LPD8806) for hours on just one 2600, 2 lasted me all night. And since they are so small, its easy to have an extra 1 or 2 in a pocket
Huh. I should have elaborated that I’m looking at 250-300 LEDs + something like a raspberry pi or beaglebone black. I calculate about 15-18A at max power. Am I being overly conservative assuming that the leds will draw an average of 20ma? What numbers are y’all seeing in practice?
I agree with @Randal_B , those rechargeable 5v packs are the way to go. I first purchased a LiPo 11.1v for a project, but I would never want to strap one of those to my body. The LiPo ran the project for hours, now with the new dithering from the library, setting the master brightness low equals >6hrs or on time for 5 meters of 12v strips.
For projects that I’ve done, I think my style of animation works out to roughly 15ma per pixel; typically I have most but not all pixels on all at once, and for each pixel usually a relatively pure hue (ie, red, or orange, or purple), which means that only “1” of the three LEDs in each pixel is lit. (That “1” might be 0.5 red and 0.5 blue for purple, for example, but the power draw is still “1 LED worth” for any pure hue. Mostly.)
I use 15ma as my working number, and try to design for bursting up to 25ma.
But that’s me and my current animation styles. It’s actually been trending up a little as I’ve started desaturating everything a little.
you’d be surprised of how low the usage will be, unless you expect to have all the leds on at once at full. I never did the actual math, but I ran my 150ish leds off 2A just fine and it was still almost too bright. You could easily get one for each leg/arm/chest…
Also, there’s the FastLED.setBrightness(…) function that let’s you adjust the brightness of the whole animation at once. So if you’re running 20% over power budget, just drop the master brightness by 20%.
(And yes, there’s a built-in function for this coming. Soon even, I hope. Couple of weeks.)
Hi Chris, I’ve been using LiPO in my RC vehicles (Copters and cars) for the past couple years and here is my experience:
LiPOs tend to get warm, even hot, when discharged rapidly. (I use a 65c 4s battery in my hex and during fast flight - it can hit 135 degrees - according to my IR thermometer. I am discharging a 5000mAh battery in about 12 minutes.
I also have a copter that uses 6s batteries and I am really disappointed in the number of charge cycles in the batteries I am using (Turnigy Nano tech).
A 6S battery may be twice the price of a 3S battery but if one of the cells in a 6S battery puffs up, then the battery is ruined. I know this from first hand experience. Consider using two 3S batteries in series to get the same voltage and if one of the batteries puffs you can replace just one of the batteries in the power pack. You could even put three 2s batteries in series to get the same voltage.
I would say LiON cells are the best choice. A LiON battery pack protects the wearer because the cell is in a can and the can is typically placed in a case. LiON is a much more mature product when compared to LiPO
LiFEPO4 is another option but the cells are rated at a lower voltage - a 4S battery is equivalent to a 12v battery. Unlike LiPO the LiFE is much less likely to burn or puff if abused or punctured.
No matter which Li solution you use, be sure not to over discharged the cells (it kills the chemistry in the anode). Most LiON packs include low voltage protection and prevent the cells from over charge. If you build your own pack from LiON cells make sure to include a charge protection circuit. For LiFe or LiPO - RC packs make sure to include low voltage protection and charge with a balance charger - at least every few charges.
If you want 1-2 amps, I tend to agree that pre-packaged USB / phone charger batteries are easy and cheap.
I have one of these $30 “13,500mAh” lithium pods and really like it. http://www.newegg.com/Product/Product.aspx?Item=0SC-001C-00011
Part of what I like is the numeric red LED (not LCD; ignore the description and look at the picture yourself) battery level indicator.
Thanks everyone for the excellent feedback! I cross posted this to the fadecandy mailing list (https://groups.google.com/forum/#!topic/fadecandy/7rzFb4Jrz0Q) and Micah reiterated the safety concerns, shared a good experience with the Ray Wu LEDs, and suggested picofuses.
Given that the article of clothing in question is synthetic (and thus highly flammable), LiPos are now off my consideration list. You’re right: so long as you’re willing to tolerate a max current draw of 2A (and it doesn’t seem like there’s anything wrong with that), there’s absolutely no reason to fool around with frankly dangerous LIPO setups. Especially when one’s costume is made of flammable materials.
Mark, funny you should mention that 15000 mAh battery. I have two of that exact model and like them a great deal. Heads up on this one: I think I burned one of those out by drawing too much power through the USB port. I was powering about 8’ of 5050SMD strip. I find that it gets fairly hot when charging an S3 at ~0.9a, so it’s probably not good for much more than 1a but I’m not sure. The manufacturer (http://www.yisenneng.com/en/ProductView.asp?ID=98) rates the discharge at 5A but that’s probably just for the 12V port. I guess one could wire-in a higher amperage 12v to 5v converter in there, but at some point it jsut gets a little silly.
Thanks for the heads up on the 12/9/5 battery; I’ve never done a heavy draw project with it. I do like that it charges at 12v, which is nice if, say, you’re in the desert and only have 12v power from a solar array.
I’m planning on lots more LEDs and I’m going to need to be able to tap ~20A. I suppose I could split the bus into sections of 2A, but that sounds like a hell of a pain. And the LiPos freak me out too.
@Mark_Kriegsman Safety is the real benefit of LiFe battery chemistry over LiPO LiFe is much less likely to catch on fire. You still need charge protection - either provided by the pack maker or use a battery charger certified for RC LiFe batteries.
Yah, I met LiFe as “drop-in replacements for lead-acid” in larger applications. I haven’t used them yet myself, because I have only one “larger application” and it’s wired into my back yard, my house, and my daughter’s bedroom – and I already have lead-acid batteries for that.
Robert, good thought. I just sent an email to the Limefuel folks. Their Amazon product specifications say “These universally compatible outputs deliver full speed charging to all devices.” which seems promising to me, but I am double-checking.
I just got a response back from them, which was, I’m guessing, not answered by someone quite technical enough:
Me: “Will the pack just “give” me 2A or do I have to set a sense resistor
on the USB plug or worse, do some negotiation with the USB host
controller in the battery pack?”
They: "The L156X output ports are designed to supply up to 2.1A from each port with two devices plugged in at the same time. Note that the device regulates the pull of power though, not the output ports. If your device only pulls 1A, the output port will only supply 1A. The output you get may also depend on the type of cable you use to connect to the battery.
So yes, you should be able to pull 2A from each output port."
Does this sound right to anyone else? I thought people had heaps of problems trying to charge, say, Samsung tablets with iPad chargers, as each manufacturer had a non-standard way of saying “No, really, give me 2.1A when I ask for it, I won’t explode, honest!”
Or is that just chargers (like this 40W bad-boy which insists each port negotiates properly for every device: http://www.ianker.com/product/71AN7105-B5A), and batteries are stupider and will just give you anything up to 2.1A at which it cuts you off to stop the battery melting?
I got a similar response from them as well. One suggestion I saw was to short out the data pins. I think it’s worth getting one of these to test. Does anyone have the ability to measure whether or not one of these is putting out 2 amps? Any thoughts on how to do so?
