Havent posted for awhile
last thing was sorting out key fob battery replacement for my Imax 2013

Key fob cr1620/cr1616
Pretty posative that my orginal key fob battery was a cr1620 but had a constant nagging feeling so pulled it apart (pic to follow) & it was actually a cr1616.
I think I couldnt find the cr1620 & found that the cr1616 was compatabil. I have had no problems now for a year with them & got spares incase
thought some might also be interested in this in howto pull apart & change (easy)