Yeah, some here have said based on the time the Yuneec batteries provide and the calculated draw, they are actually 6300mAh batteries which have been mislabeled as 5400mAh. To be safe and take Yuneec at their word, i.e. 5400mAh, then 5.4 amps would be an industry standard of 1C charge rate. Keep in mind though that your charger needs to be capable of at least 90.7 watts to do this. My ThunderPower AC/DC charger will only do around 70 watts on AC so I'm limited to around a 4 amp or 0.8C charge rate unless I connect it to a 12v DC car battery.
Yuneec's charger charges at 0.5C or 45.4 watts and takes 2 hrs to fully charge from empty. 1C reduces that time to 1 hr assuming that's from LiPo battery empty (which isn't really empty). To extend the life of your batteries it's better to not go to empty or the low voltage cutoff warning which is why MM1992 is getting 45 minutes to charge at 1C or 5.4 amps.
A simple formula to remember for a safe 1C charge rate is to look at the battery label for the mAh then use mAh / 1000 = Charge Amps so 5400mAh / 1000 = 5.4 Amps or 200mAh / 1000 = 0.2 amps etc.
There's lots of good discussion here around batteries if you use the search.
