HiFiBerry DAC+ RTC
This is an OEM DAC specifically addressing the needs of business customers. It combines a high quality 192kHz/24bit audio DAC and and RTC module. The real-time clock allows to set the time of the Raspberry Pi even if no network connection is available.
The board comes without a battery. The battery is a standard CR1220 cell.
Configuration for the RTC chip can be found here
RASPBERRY PI A+/B+/2B/3B/3B+/4B+/ZERO