RTC DS1302 Real Time Clock Module for Arduino AVR ARM PIC SMD Module operating voltage compatible 3.3V/5V, can be connected with 5V and 3.3V microcontroller DS1302 is made large 8-pin DIP chip, chip below IC socket for easy replacement and swap chips Backup battery is genuine celestial CR2032, Voltage 3V, current 260mAh, non-rechargeable batteries. Theoretical data retention time is more than 10 years! Crystal 32.768KHz, matching capacitance 6pF, size 2 * 6mm