Apple markets the Air MacBook with a small 45W charger. By way of comparison, the MacBook has a 60W charger and the MacBook Pro 85W.
MacFixit reported that it would be a little small for the machine. In the case of intensive use, plugged in, the battery will virtually not recharge at all. A completely discharged battery can take 8 hours to be recharge fully, which is too long. Appleinsider reports that the time is reduced to 5 hours using the charger from a MacBook ( which requires raising machine for connecting the larger MagSafe ).
Note: It looks like a bug to conclude that the (re)charge is much faster on an off-machine as compared to a machine-on-standby, since consumption in standby is very low.
It is also possible that Apple preferred a slow battery charger to prevent the risk of a dramatically swelling battery (as has been the case on some MacBook P
