How to start LIFT Foil drive without original Battery?

I got a LIFT Foil drive unit that is suppose to work

Motor/Mast, Controller box, Remote but not the battery

I already opened the controller box and it is nice and simple.
I can turn it on and a blue light is flashing but it runs from a 9V Battery (inside the controller box) to do all the checks and then as I understand it checks the battery and then turns the main battery on (contactor in the battery). There is a communication cable for the battery!

How could I trick the system to switch to the main battery?
Any ideas?

If nothing is working it is easy to use all the connectors in the controller box and just use a VESC and your own remote! But would be nice to be able to just use the system.