So the odyssey in my recent RV-12 purchase is six years old and needed to be replaced. I did some research and opted for an EarthX. I spoke with the Company, and they said the EXT680 will replace the Odyssey pc680. I asked if the EXT900 would be "ok" since it added some additional power and the price difference wasn't much. They said "yes, either would work". I purchased the EXT900 from Aircraft Spruce and installed it this past Saturday the 29th. Friends of mine rotated out today and they had to turn back....twice. The charge showed 13.5 on the Dynon and was "yellow" instead of "green". The fuel pump fuse blew and the engine RPM on the Dynon fluctuated between 5500-7500. There was no diff in engine sound so I don't believe the fluctuation was actually occurring however it was crazy on the Dynon. Then they momentarily lost power. They returned, did a ground runup with no incident and rotated again after replacing the fuel pump fuse. They had to abort the takeoff roll after losing power. IN reading some articles, a different regulator is needed in order for the EarthX to work? They recommend one I can't even locate to get a price on; A Schicke GR6. I have no desire to start swapping out regulators. These issues only appeared after installing the EarthX. Anyone out there have to change the regulator to make a Lithium-Ion work? Again, this airplane has been flawless and these issues happened today, first flight after installing the EarthX. I look forward to some feedback and no, it is not an "IS" model Rotax....twin carbs....with only 80 hours on the entire airframe/powerplant.