Was the phone turned on while charging?
I have the problem, that the battery will charge only when turning on the phone; while it is turned off, the percentage does not rise above 5% and the phone turns hot.
Turning it on, the charging is back to normal.
The “kickstart” procedure for the battery has changed as far as I know.
Let the battery drain till the phone shuts itself off.
Take the battery out and leave it that way for 30 minutes.
Then put the battery back in and only then charge until the battery is full.
Possibly you have to do this twice.
I think this procedure applies to the FP1 as well:
in response to:
I would interpret the “yes” from @borjan as a statement, that the kickstart procedure has changed for the FP1 as well.
Maybe he reads this posting and can clarify on this.