Notice: Function _load_textdomain_just_in_time was called incorrectly. Translation loading for the updraftplus domain was triggered too early. This is usually an indicator for some code in the plugin or theme running too early. Translations should be loaded at the init action or later. Please see Debugging in WordPress for more information. (This message was added in version 6.7.0.) in /home/frankliuao/frankliuao.com/wp-includes/functions.php on line 6114
How to know the charging/discharging speed of your MacBook – Ao Liu

How to know the charging/discharging speed of your MacBook

/ General, Life in the U.S., Tutorials / By

I recently encountered this problem when the charger of my MacBook 11” was stolen in the library. I had to use a USB charger for my Samsung Galaxy to charge the laptop with a micro-USB to USB type C converter. Obviously it wasn’t quick enough so the net effect on the battery was discharging. I have a few phone chargers, and a portable battery, so I would like to know the charging/discharging speed.

After some Googling I found the system command system_profiler. It lists all the system information about your Mac. To follow the following instructions, you need to have Terminal (Launchpad-Other-Terminal) opened.

First I’ll use a MacBook Pro 15”, mid 2015 as an example of displaying the discharging speed.

The charging/discharging speed is basically indicated by the battery current. If it’s negative it means your battery is discharging and vice versa.

I fully charged the laptop and waited until the battery went to 99%. I then did

system_profiler SPPowerDataType

and saw the following information about the Battery.

Notice the Amperage (mA) and keep in mind that it might change a little based on your activities but it should always be negative if you don’t connect to a charger. You should repeat this a few times to get a rough estimation about the basic power consumption of your laptop. If you don’t want to see so much information but only the Amperage, use

system_profiler SPPowerDataType | grep -I "Amperage"

Typically there will be some delay but it doesn’t matter. See example below

Now if I connect the charger (85 W) it shows a positive Amperage indicating a fast charging

The estimated Amperage of a MacBook 11”, with minimum activities (only Chrome opened and no “significant energy usage”) of different chargers are:

  1. A Samsung Quick Charger (for Galaxy S7 edge) + nanoUSB cable + nanoUSB to USB C adapter: Roughly -200 mA. Even though you turn off the laptop, charging speed is super slow.
  2. A Samsung Quick Charger (for Galaxy S8 edge) + USB C cable: Roughly 0 mA (so if you turn off the laptop it should be charging quickly enough).
  3. A Samsung normal charger (for Galaxy S6 or earlier) + nanoUSB cable + nanoUSB to USB C adapter: Roughly -300 mA. Even slower than 1. Almost not visibly effective charging.
  4. A portable battery, marked up to 5 A: Roughly -100 mA. Slow but useful.

So, if you lost your original charger, you may use a Samsung USB C charger and its cable and shut down your computer for temporary rescuing. Or, you have to buy a good charger from Amazon…