ORIGINAL: mclina
If you are using the stock cigarette-lighter charger, that may be the problem. I had this problem with an Aerobird, where the charger would say it was full, but it wasn't.
mclina,
I also have an F27 that would not fly and took your suggestion regarding charging and charged my two batteries last evening on my field charger and wa la she flies went right up this morning.
Thanks for the input.
Gary