For others who are interested or have similar problems, I can tell how I managed to solve this.
Just to clarify: The Di2 8050 is compatible with EP800, but not the 8150.
I spoke to Shimano Technical support and they said the folowing:
"As a private customer, you probably cannot reprogram the...
Hi,
I have a Rock Machine Blizzard Int e70-297 E-mtb with a Shimano EP8 motor and was thinking of using the opportunity to upgrade to electronic shifting.
All said and done, I went and bought a new XT rear derailleur (RD-M8050) and shifting unit (SW-M8050-R).
The problem is that when I...