As we make the transition to a mobile system, we need to consider how the Pi will be powered. There are two kinds of batteries that are most relevant to our needs. First, there are primary batteries, such as the disposable, non-rechargeable style used in many appliances such as keyboards, mice, and torches. Second, there are the rechargeable kinds, such as those in a cellphone, a camera, or toys such as RC-cars that get used often.

The Raspberry Pi is not an ultra-low power device and is usually turned on for long periods of time, which makes rechargeable batteries the best solution. The most common rechargeable battery technologies are listed in the following table showing a performance comparison of various rechargeable batteries: