How to measure the charging speed of your iPad/iPhone (and set a charge alarm)

I was recently able to confirm that a certain new charger that I tried out is able to charge my iPad Pro (2017) about twice as fast as the original charger. (My results can be found at the very end of the article.)

NOT by using apps such as Ampere, which despite the many positive reviews provide wildly inconsistent results. Multiple runs with the same charger and cable resulted in numbers that were up to ~200% off from each other!

Instead, I realized that Apple’s own app Shortcuts can be used for pretty decent benchmarking.

Measuring charging speed

It’s done by triggering notifications that contain timestamps at different battery levels. Personally, I used 50 to 60%.

1.Add an “Automation” shortcut that triggers when the battery level rises above 50%.

2. For the action that it should execute, add Scripting -> Show notification.
3. Change its text to something that contains a “Current Date” variable.

4. Tap on the variable in the notification text to change its date format to None and its time format to Long.
5. Automation tasks will trigger as soon as you create and enable them but you need to disable “Ask Before Running”, otherwise your device will show a prompt whether you want to run the script instead of the notification.

Now do the same for 60% and you will be able to time how long it takes different chargers or cables to charge those 10%.

Estimating the wattage

If comparing times isn’t enough for you and like me, you curious how the wattage compares to what the charger is rated for, you need to know how much we charged in the time remeasured above in mAh.

Which can be done using the tool iMazing. Just check the charging capacity of your device at the percentages that you used above. Once you have that difference in mAh, convert it into Wh using this calculator, with 5 V as voltage (just in case that this changes in the future — you might want to google whether that is actually the voltage of the battery in your device): https://milliamps-watts.appspot.com/

Then, the formula to get the wattage is: (60 / charging time in minutes) * charge amount in Wh

Setting a charge alarm

With iPhones, I suppose the optimized charging feature makes this unnecessary. But iPads of course charge to 100% without notifying the user.

So here’s a shortcut to deal with that:

1. Add an “automation” shortcut that triggers when the battery level rises above 80%.
2. For the action that it should execute, add Apps -> Clock -> Start timer.
3. Set the timer to be 1 second.
4. Once again, make sure that it is set to not ask before running.

My results

Unfortunately, I chucked the original 12 W charger a while back when I realized that even my old Anker PowerPort+ 1 (15 W @ 5 V) charged a bit faster, so I wasn’t able to compare directly.

But I compared an Apple 30 W USB-C power adapter, as well as a Anker PowerPort+ Atom III (45 W through USB-C) to the PowerPort+ 1, using different cables. Running some of the tests twice.

Overall capacity: 7169 mAh
@ 51%: 3685 mAh
@ 61%: 4397 mAh
Difference: 712 mAh
=============================================
Apple 30 W charger & Apple USB-C cable: 10 min. (~21.3W)
Anker PowerPort+ Atom III & Apple USB-C cable: 11 min.
Anker PowerPort+ Atom III & Anker USB-C cable: 11.5 min., 11.5 min.
Apple 30 W charger & Anker USB-C cable: 12 min.
Anker PowerPort+ 1 & Apple USB cable: 16.5 min., 18 min. (~12.5W)

Given the 15 W rating of the Anker PowerPort+ 1, that seems close enough. And I guess the battery of the 2017 iPad Pro model just can’t handle more than ~22 W.

But I tend to charge my iPad from 20 to 80% (I also have an automation for a low battery notification that uses Documents -> Speak Text instead of a timer) and that now happens in roughly 65 minutes instead of 100. And with the original charger it was probably more like 120. 😮🚀

Credits to Jake Peterson of gadget hacks, whose article made me aware of this being possible thanks to Shortcuts.