MacBook – How to power the MacBook Pro during trans-Atlantic flights

I've had a similar problem before and the charger wasn't completely broken. Here's what you can try:

1. Plug you MacBook in some other location (seriously, it can be problem with the current in your location)
2. Plug the cable in the opposite way (I mean attach the charger to you MacBook in the way it caps the Ethernet plug).

If it won't help I am afraid you'll have to buy new charger. I would suggest trying another charger before buying a new one to determine if it is your charger or your Mac.

The problem lies in one little word: Modified sine wave. Which typically has a rather tenuous connection with an actual sine wave. Rather, its voltage is a periodic step function with rather few steps (though I can't say for sure about the specific model you mention). You need an inverter that provides the latter. They exist, but tend to be more expensive. I use one made by Mascot, and it charges my macbooks just fine. My previous inverter, with its modified sine wave, did not.