can I charge my 50W MacBook Air (mid-2011) with my old 45W L-type a/c adapter? TIA

It's not recommended. You can use a higher capacity charger on a system which needs less, but you should never use a lower capacity charger on a system which needs more.

It puts too much strain on the lower power charger (gets too hot also).

Better off to get another same or higher wattage charger

Cheers!

Joso3 wrote:

not concerned with taking longer to charge, just don't want to fry anything. Thanks.

NO NO NO!!!!! You can change with a higher rated charger (60 watt or higher) but not a lower wattage model.

I ran a 15" MBP off the MacBook Air 45w adapter for 3 straight weeks in the field because my primary charger died and I was 600 miles from anything Apple and access to shipping services. Ideal? Hardly... took forever to charge and if I ran the machine with the power adapter connected it would frequently say "Not charging."

But it'll work, just far from ideal.