Originally Posted By: andy
Also, Apple ship a range of laptop power supplies of different capacities, all of which have the same connector (for the current range of models, mostly at least).

If I plug the PSU from my old MacBook into my current MacBook, it doesn't actually have enough power to charge the battery when all four cores are running at 100%.
Are you speaking of Mag-Safe power supplies or the USB-C power supplies?

Interestingly, with the USB-C ported MacBook models they are able to be charged with power adapters as meager as the iPad 10 watt brick (with laptop turned off). A traveler can charge all their portable Apple devices (iPhone, iPad, MacBook) using a single rather compact power brick (such as this Anker PowerPort + USB-C) , albeit at a modest (overnight) pace for the laptop. A single aftermarket power brick sporting both USB-C and USB-A ports works well for an Apple based traveler.