The video said 4 batteries I believe. One in each shifter like a watch battery that lasts a year. Then interchangeable, rechargeable ones in the DR's that last 1000km/620 miles.

The cool thing they hinted at is if your RDR battery goes dead on a ride, you can pick a front ring, then move the battery to the RDR and get home.

As soon as it trickles down to Force, I'm upgrading my bike. Sounds like you can run whatever crank you want, btw.