Battery not included. It is an extremely accurate i2c real-time clock (RTC), with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. The device incorporates a battery input, disconnect the main power supply and maintains accurate.
Operating voltage :3.3 - 5 .5 v
Clock chip: high-precision clock chip ds3231
Clock accuracy:0-40 centigrade range, the accuracy 2ppm, the error was about 1 minute
