ST2-S battery(s) recharge technique?

[MinnBobber]

Hi, Stromer ST2-S question: It has main battery and Di2 XTR small control battery.
How exactly can one charge the Di2 from the main battery?

I know it is doable but I expected a small device plug-in receptor on the Di2 handlebar gauge. I found a medium device connector under the rubber flap ----plugged in one end of my medium-to-small connector cord . Cannot find where to connect.
Any help greatly appreciated.

What else besides the medium connector receptor is under the rubber flap?
Thanks

 

[Ravi Kempaiah]

You don't charge your Di2 XTR battery from the main charger.
There is a separate charger for the Di2 battery. Look into your battery/manual box.

Here is a video explaining how to do that.