Charger should be fine if it charges at all.
I see to scenarios:
- The last 10% of Li-Ion batteries normally take much longer to charge than the rest (check e.g. here). --> Wait some more time
- As your FP2 and its battery is new, you should give them some charge/uncharge cycles until firmware/android can calibrate correctly to this specific batttery and the battery itself get used to be used (informal spoken)
In general one should not routinely charge above 80/90% since it could decrease battery health in long-term.
More info you can check here.
Cheers, RObert