henry_blackie wrote:If you get a battery pack that's too big will it break the Pi? I've been looking at mobile phone chargers and am not sure what size I should get.
A bigger battery pack provided it supplies the correct Voltage will not break the Raspberry Pi, it will simply run it for longer.
Most of the battery packs sold as mobile phone chargers, that have a 5V USB style socket on it should do the trick. Any that are rated at 500mA, might be problematic if you try and connect loads of USB devices to the Raspberry Pi at the same time though. Generally speaking the packs are at least 1A, and some are rated at 2A.
Ones that charge from a USB source like my iEP387 can usually only supply power to a device, or be charged. They can't do both at the same time, so cannot behave like a mini-UPS.
Ones that use a higher Voltage to charge and use a non-USB type connector for input power, often are able to provide a regulated USB 5V output at the same time as being charged, and might be able to behave like a mini UPS.