Interfacing RTC BQ3287

Hello people,

i started working with a RTC BQ3287 and connected it like in the project from after starting it up by sending 'i' via the Serial console and it starts counting seconds and works perfect. According to the manual, the 3287 series contains already a backup battery. if i disconnect my arduino from power source and reconnect it after some minutes, it holds the Time, but if it is disconnected for more then 2 hours, i have to reinitialize the clock and set the time again. Do I have to set anything in the Clock, or is my english so bad, that i missunderstood something in the manual?

Best Regards, Martin

I'd try a new battery.

Thanks for your Response. In my opinion, it says in the manual, it has a builtin battery for backup. I dont have pins to connect a second power source for backup.

Do you have a link to the RTC that you have? If it has a battery backup, the battery should be replaceable. What do the makers expect you to do when the battery goes dead?

Hi Paul, the link to the datasheet is It says: "The bq3287 is functionally equivalent to the bq3285, except that the battery (16, 20) and crystal (2, 3) pins are not accessible. These pins are connected internally to a coin cell and quartz crystal. The coin cell is sized to provide 10 years of data retention and clock operation in the absence of power." This means for me, that if my arduino is powered down, the RTC is still counting his seconds up.