The EPS Power Unit is the systems source of power as well as the "brain" of the system, responsible for managing the battery pack, enabling and monitoring the front and rear derailleurs and communicating with the Interface Unit. Features: Weathertight, o-ring sealed connectors Lithium Ion battery duration: 500km/month - 1500km, 1000km/month - 1800km, 2000km/month - 2000km Water proof to 1m for 30 minutes (IP67 Rated) Operational temperature: -4F to 140F Charging temperature: 32F to 113F