Can you use a less powerful charger to charge a laptop?

September 4, 2017 8:57 AM

My work computer is a 15" MacBook Pro, and it has a beefy 87w adapter. I also have the 60w adapter that comes with the smaller MBP. I know using a less powerful adapter will charge the computer more slowly, but besides that, is there any downside to using it? I would just be plugging it in when the computer is not in use.
posted by bluefly to Computers & Internet (7 answers total)

Best answer: I have a work 15" MBP and charge it with the charger from an 11" MB Air. The charger does get warm, but has held up very well the past few years.

The charger will charge more slowly, and does get hot. If you are using the discrete GPU instead of the onboard Intel video, it will not be able to keep up. Check your settings under "Energy Saver".
posted by nickggully at 9:11 AM on September 4, 2017 [2 favorites]

It works fine it is just slower. You can also charge the smaller machine with the bigger charger, though it probably won't be any faster.
posted by rockindata at 9:14 AM on September 4, 2017 [1 favorite]

True, when looking at a charger you will find two numbers that are important: Output Voltage and Output Ampere. You can mismatch the Ampere, but not the Voltage. Using a 12V charger on a 9V device can produce some smoke and sad feelings.
posted by nostrada at 3:30 PM on September 4, 2017 [1 favorite]

Apple's official response
posted by blob at 5:10 PM on September 4, 2017

Apple's response aside, I did this for years with no side effects as far as i can tell. The 15" MBP (older magsafe) charger lives at work, and my personal 11" Air charger was at home. I used the air's charger with the MBP all the time. I've probably also done the reverse, but without any regularity (as i don't often have my personal laptop at work). I've since upgraded my personal machine (the air) to a new usb-c charging MBP, so this setup no longer works for me and i'm rather annoyed at having to drag charging cables everywhere now.
posted by cgg at 8:03 PM on September 4, 2017

Best answer: I've done this for years, and it worked (different MacBook models, but the same scenario). The only problem I've seen is that if the battery is completely drained (heavy usage and you ignore all the low battery warnings until the computer powers itself off), the MacBook Pro might refuse to boot until you plug it back into the higher wattage charger. No permanent damage was ever done, but make sure you have access to the 87w just in case.
posted by bbuda at 10:16 PM on September 5, 2017

Response by poster: I had read Apple's support page, but they just say the lower wattage adapters don't provide enough power; not that they are bad for the computer. Since I just want to charge the laptop overnight when I'm not using it, I'm ok with it charging slowly.

Thanks, everyone! Especially the advice to check "automatic graphics switching" option which I did not know existed.
posted by bluefly at 7:50 AM on September 9, 2017