As I got my FP2 today I tried my old original FP1-charger for it, which worked.
Power consumption during charging, phone power off (measured with a power meter):
FP1: P=5.5W => 1,1 A if 5V is provided => calculation: 1h50m for a full charge (2000 mAh), ~2h in reality!
FP2: P=7.7W => 1,54 A if 5V is provided => calculation: 1h36m for a full charge (2450 mAh), if linearity is assumed
Thats only with the original FP1-charger to give you some minimalistic values, what the FP2 should do.
Most likely the power is limited by the charger (output 1.0A@5V), which should be already for the FP1 at his limit. I am quite surprised, that he can deliver 150% of its designed values.
(btw: it gets noticeably warmer than with the FP1 and makes some noise. Hope it will not die)
Edit: after beeing commented here:
If we multiply numbers with 80% efficiency of charger/FP-electronic we end up at FP1=0,9A and FP2=1,2A, which would mean full charging time would be FP1=2h13 and FP2=2h03m.
Charging of Li-ion battery is quite linear in time up to 90%