I wanted to see inside the Robomaster S1 battery so I pried off the end. Here are some photos of the battery guts.

Here's the main battery PCB after a short press of the button.

As can be seen, the battery is made from three 18650 2,400mAh cells. Each cell is labeled LGABHE21865.

The ten connector interface uses four separate lines. Four connections are used for ground and four connections are used for full battery voltage (about 12V). The two center connectors are used to communicate with the robot. One of these two center connectors is also used to communicate with the battery charger.

Edit(210327): There's a data capture of the I2C communication on the DJI forum.