LilyPad Basics: Powering Your Project

Contributors: Gella
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How Long Will My Project Run on Battery Power?

To figure out how long your project will run on battery power, you need to know two things:

  • how much current your project uses
  • the capacity of your battery

Battery capacity is given in milliamp-hours (mAh). This number tells you how many milli-amps (mA) a full battery can provide for one hour before it’s empty. The e-Textiles Battery that comes with most LilyPad Arduino kits has a 110mAh capacity. For many projects, especially ones with a large number of components such as LEDs, you will probably want to use a higher capacity battery for a longer run time.

To find out how long a battery will last, use this formula:

Hours = Battery mAh / Project mA

Thus, an e-Textile battery will only power the project for approximately half an hour. Here's an instance where a larger capacity battery would make sense, if the project needs to operate for a long time, such as during an event or showcase. The trade-off is that a higher capacity battery is also physically larger -- make sure to plan accordingly for proper battery storage/attachment on your project to reduce strain on the wires and fabric.

Here are some typical runtimes for various SparkFun batteries and numbers of LilyPad LEDs/LilyPixels:

Number of LEDs1251020
Battery NameBattery mAhHours of Operation
Polymer Lithium Ion Battery - 40mAh 401.
E-Textiles Battery - 110mAh (2C Discharge) 1103.
Coin Cell Battery - 20mm (CR2032) * 2508.
Polymer Lithium Ion Battery - 400mAh 40013.
Polymer Lithium Ion Battery - 850mAh85028.317.
Polymer Lithium Ion Battery - 1000mAh100033.320.
Polymer Lithium Ion Battery - 2000mAh200066.740.
Polymer Lithium Ion Battery - 6Ah6000200.0120.054.528.614.6

* Note: the Coin Cell Battery is non-rechargeable.