My MBA MagSafe 2 charger had to be retired due to frayed cord. Is it safe for my MBA to use a higher wattage charger than the standard 45 watt unit? I'm presently using an old 85 watt unit that has a MagSafe 1 connector with a converter head to make it a MagSafe 2. I would rather have a true MagSafe 2 connector, but unless I want to pay Apple $79, the easiest option is a higher wattage unit. I see them advertised for $25-$35. I'm guessing a higher wattage unit charges quicker, but that is almost meaningless to me.