Prague-based UUGear have released a new version of their Witty Pi board for the Raspberry Pi. It is a power management board that can accept battery sources (via a XH2.54 connector) of up to 26V (although anything higher than 8V and you’ll want to investigate heatsink options) and provides a real-time clock for your Pi. It has a microcontroller (ATtiny841) on-board to do complex power up/power down operations. All the configuration is done through the I2C interface and there is a web application to help deal with your scheduling requirements.
You can get hold of the Witty Pi 3 by visiting their website. It costs 530 CZK which is approximately 20 Euros, £19 or $23.50 making it a very cost-effective solution for powering your Pi by battery and scheduling uptime to get the most out of the power source.