Hannes.
Their documentation is messy, but this is what I have figured out so far:
1. Battery 1 dip switches 1 up, rest down, Battery 2 dip 2 down rest up.
2. Cables. You need to use RS485 from one battery top the next. See below. You can use a standard lan cable.
Battery one RS485B >> Battery 2 RS485A
see image
3. Connecting it to a pc, is also sucky
you can use either the RS232 port or the open RS485 port on battery one and link to a pc.
RS232 pinout