What I’ve learned the past few months using LiPo batteries and a UBEC voltage regulator with a LED hat project
Have a fuse between the UBEC and your power hungry LEDs. I broke my first UBEC by uploading the wrong sketch that displayed full-white on all LEDs. After 3 seconds the lights stayed off forever
Have a battery alarm connected. I broke one battery by leaving it attached to the hat over night. The battery pack looked like it had been stung by a bee in the morning.
Turn the brightness down. The battery lasts longer this way. 488 LEDs at brightness 32 (1/8th) last 7-8 hours with a 3-cell, 3000mAh battery.
Think of the extra weight you put on your head. The battery alone weighs around 300 grams, I noticed my neck straining after the second day of wearing it on an open air music festival.
The hat and battery are extremely sturdy and survived rain, heat and even the mosh-pit at several concerts without any problems.
Thanks for sharing. However #2 might be a good sign to reconsider lipos for wearable tech, it’s a bit of an unstable battery chemistry imho. (I store ours used for rc hobbies in ammo boxes.) They are hazardous material on planes for good reason. We just neutralized one puffy battery the other day with pellet gun for the fun of it… I’m glad yours didn’t ignite, but they scare me… Don’t get stung by that puffy bee!
Fwiw we use LiFe types in the expensive transmitters because they are a bit more forgiving and stable, but they can also puff.
LiFe chemistry and cylindrical cells are an easy way to keep your lithium-powered devices safe and convenient.
I’ve used R/C squishpacks for past projects, and while they have ridiculous energy density, wearing them I’m always on my guard just in case the battery decides to be on fire at any point.
I’m going through just the same issues with my hat.
Last night I broke a UBEC on my staff, just from the start-up power demand of the strips before the Teensy was alive and controlling them. Admittedly, I’ve a lot of strip and tiny UBECs, but they definitely need protection against over-power and over-heat. I don’t know if a fuse would be fast enough to protect them, I’m planning on trying a big MOSFET between battery and strip. This would allow the Teensy to start the strip (and solve the huge power drain when strips are connected but off).
I’m using lithium-ion protected cylindrical cells. That way, the battery can run to flat without getting damaged. Also, less likely to catch fire while attached to you. I wouldn’t use LiPos for that reason alone.
Yeah, obnoxious lumens are fun, but if you want to actually be able to talk to someone without getting them a welding mask, then all the way down. I’m often running at 4/255.
A friend made me a leather pouch for the driver that sits on my waist. So much easier. I’m a big fan of putting all the gubbins in a solid case. Getting a really flexible cable also helps here, 4-core 0.2 mm^2 is all I’m using for 430 LEDs.
@Jez_Weston
What you want to avoid using is the pouch type batteries, which don’t have a solid casing to protect them – they’re super unsafe for wearable projects.
Li-po cells can be in cylindrical packages for durability. While the chemistry isn’t distinct[1] from Li-ion, they do offer better specific energy (Watt-hours per kilogram) than non-polymer Li-ion cells. They’re also available with protection circuits.
