Wow...
maybe I've been doing it wrong.
For recharging, mine always seem to take too long.
My slim batteries, 65a/78a/78m, take 2-3 hours to charge, regardless of power brick/PC used. The difference in charge time seems to be a function of quality control of the battery, not the battery size. My little blue 78 is the fastest at charging, consistently under 2 hrs, and 1 65 takes 2 hours, and 1 65 and 1 78 both take 3 hours.
On my x2's, 650 & 900, both take about 10 hours to charge. This is regardless of method used [always use the cable that came with it].
0.5a, 0.5a, 0.75a, 0.8a.
The only thing I have not tried is the SI branded 1.5a brick. Based on my results, it seems more amps have zero impact on charging. I am not really interested in the passthrough function. Should I really expect the charge time to drop to 3-4 hours if I buy the SI brick???