So, you want to build something wearable but you're not sure how to power it?
You're in luck: today I'm going to help you pick the right battery for your wearable electronics
project.
First, it's important to know how much power your circuit uses.
For most circuits, just look up the maximum current draw for each component, and add them
together.
Then pick a battery that matches or exceeds your amperage needs.
This 1.5v rechargeable AAA battery stores 750 milliamp-hours, which means it can theoretically
output 750 milliamps for an hour, or half as much current for twice as long.
If you have three in a battery pack, it can give you three times the voltage, 4.5V, at
the same 750milliamp-hours.
My FLORA, GPS, and eight NeoPixels, on blue only, total up to 210 milliamps of current
draw.
So this three AAA pack can easily run the project for about three hours.
In reality your pixels are probably not on full brightness all the time, and will therefore
draw less current than you calculated.
This power supply overhead is a good thing and means you're not going to overtax your
battery.
You can also just measure the current draw of your circuit using a benchtop power supply
or a multimeter.
I usually prototype my projects using a plug-in power option, then switch to battery power
later.
It's just one fewer thing to troubleshoot.
We have a bunch of different flavors of alkaline battery holders to suit your different needs,
from this waterproof two AA holder all the way up to four.
Each battery adds another 1.5V to your total voltage.
For most wearable projects, stick to 2 to 4 Alkaline or rechargeables for about 3 to
5 volts.
Alkaline packs are great-- the batteries are easily replaceable and the hard plastic keeps
everything safe.
But if you're more advanced, you might like these power-dense and lightweight lithium
ion polymer rechargeable cells.
These batteries come in many shapes and sizes, and require a special charger to fill them
up.
Some are small enough to wear on earrings or other jewelry.
Lithium cells are more delicate than alkaline battery packs and for this reason need more
care and attention to prevent from being damaged-- you should never bend, puncture, crush, or
otherwise abuse these batteries.
I often wrap them in gaffer's tape when embedding in projects, like here on the NeoGeo watch
and in the pocket of my winter coat.
Lithium batteries can get hot during charging so they should also be charged off of fabric
or the body.
For that reason, we have a separate charger board.
Unplug the battery from the connector to recharge from any USB port.
For GEMMA projects, a slim battery holder with a built-in power switch is handy.
Coin cells are fairly high capacity for the size, this pack can give you about 6V and
250mAh.
However, it can't provide tons of current for long periods of time, this pack can power
a gemma plus three or four neopixels for a couple hours-- pack spares in case the party
runs long.
Many of you ask how to power a large number of pixels on the go, like on a video jacket.
Sure, you could wear a huge 6V lead-acid battery in your backpack, but these days there are
some lighter-weight options available.
For easy charging, nothing beats a pack of Nickel-Metal-Hydride batteries.
Three AA's will power most projects, four AA's will alleviate the voltage drop that
occurs over long lengths of conductive textiles.
Instead of some long runs of thread, consider soldering in thin wire-wrapping wire instead.
Another way to deliver juice to your power hungry wearable is through these USB battery
packs.
We sourced them for the Raspberry Pi, but this bigger one can deliver up to two amps,
enough to charge your iPad, and has 10,000 milli-amp hours of capacity.
FLORA is designed to handle 2A through the protection diodes with ease so you can just
plug in the pack into the USB port and it can drive up to 100 NeoPixel LEDs.
We hope this helps you pick the perfect battery for your project!
Check out the batteries, holders, and chargers in the Adafruit shop, and if you have more
questions, post them in the comments and I'll answer them on our live show, Wearable Electronics
with me, Becky Stern.