RTC Backup BatteryLithium primary battery to back up the Real Time ClockThe below listed ODROID boards has RTC circuit. You need to just connect this backup battery to keep the time when your ODROID is offline. This battery can keep the RTC running up to 3 years without external power supply. The list of the board that RTC circuit implement. ODROID-XU4ODROID-XU3 / XU3LiteODROID-C1 /