Hi Dave. I bought a third-party charger for my Apple MacBook Pro and it works, but really slow. Much slower to charge than the original Apple unit. How can I tell if it’s working properly?
Ah, you’ve opened up a Pandora’s Box of complexity when you move to third party anything in the Apple ecosystem. Cables, chargers, both can have a surprising effect on your power and charging experience with a Mac system in ways that are not at all obvious. Even with an Apple charger, if you have a USB-C system like I do and use a third-party cable, that cable itself might drop the wattage down and slow down the charge. Yikes.
In fact, I learned some things about charging systems as I was writing this post, so I should thank you for your original question! First off, the key variable is wattage and it’s calculated easily as amperage * voltage. Apple has four different chargers depending on your notebook or computer model: 29W, 45W, 60W, and 85W varieties. The very latest bump up slightly so my MacBook Pro with TouchBar has two official Apple options 61W and 87W. Key to realize: the wattage specified isn’t necessarily the wattage that the computer receives when charging.
To start, plug in a charger. Any charger. Then go to Apple > About This Mac. You’ll see something like this:
See the button labelled “System Report…“? Click on that, then scroll down on the left side to find the “Power” entry. Click on that, scroll down on the right side of that window and you’ll get this information:
Look at the “Name:” field first. That shows it’s a proper Apple 87W USB-C Power Adapter, and even shows its serial number. Most importantly, though, look at the “Wattage (W)” field, which shows that the computer is getting 86W of power, a fast charge for this device.
Now, let’s try swapping out the Apple cable for a third party USB-C cable and watch what happens when we relaunch the System Report:
You can see the problem, right? 87W charger, but only 60W coming in to the computer for charging. In other words, a faster charger, but a slow charge.
Note that the correct Apple cable and a lower wattage charger reports as you’d expect:
Now I’ll try a third-party 60W charger that should work just fine, at least according to the vendor. But when we plug it in and check the System Profile information, well, the truth is shown:
Not only do you not see any identifying information, but it’s only giving 55W to the computer, which categorizes it as a non-charging plug, denoted by “Charging: No“. Definitely not good!
How can this happen? Because there are a ridiculous number of third party vendors selling MacBook chargers, as you can see when you do a search on Amazon.com:
There’s just no good way to navigate this chaos, and once you start looking at the photos of the products, they’re just about all trying to look exactly like the Apple product too:
The moral of the story? It might just be worthwhile to pay the extra and get a proper Apple charger and, as applicable, Apple charging cable to go with it. Because paying for a fast charger that doesn’t work correctly is just a bad idea.