Firstly sorry for my English, I want to add a rtc feature to my board but i don't have enogh place for rtc, eeprom, and external battery on my board. I'm plannig attach a DS3231 to my board. My board is also working with 1 cell rechargable li-po battery. Is it possible working DS3231 with this battery?? I mean, if i connect parallel my board and Vbatt pin of ds3231 to battery, and if i use a 3v zener diode (or ldo which can break the circuit under 3v) input of my board, can i use the other (between 2.5 and 3 volts) part of my battery as a externall battery (like cr2032)?? Also do i need an eeprom to use DS3231 because i usually see it with an eeprom.