26 January 2023

How to stop your iphone charging at a defined percentage

A lot has been said about managing battery health on laptops, phones and even electric cars. There seems to be some consensus that charging to 100% all the time puts stress on the battery. Many electric car manufacturers allow the charger to stop at a user defined level, and Apple even introduced optimized charging on its phones and Macbooks.

From reading around the topic and how Apples optimized charging works, it doesn't seem to be only charging to 100% that that stresses the battery, but taking it to 100% and then holding it there by leaving the phone plugged in for a long duration.

You can see this in action on a Macbook that is usually plugged in. Sometimes the battery will drain down to 80% and stay there for some time, or charging will stop at 80%.

Once an iPhone learns you normal usage patterns, when plugging in overnight it tends to charge to 80% and then holds back the final 20% until your normal "unplug" time.

Apple doesn't give any fine grained control over this process. For example, it might be nice to have a "max charge" setting, but it isn't available. On laptops there are 3rd party applications you can install to set the limits but on the iPhone, nothing exists.

My last iPhone was an iPhone 7, which I often had plugged in during the day for tethering, or when at my desk and left plugged in overnight. The second battery barely lasted 2 years before it was losing charge very quickly.

After replacing the iPhone 7 with a new iPhone 13, I wondered how I could stop it charging at 80%.

Apple provides no way to configure the charge limit, and no 3rd party Apps can do it either.

Then I came across Chargie. This is a clever device you plug into your charger, and then plug the charging wire into it. It connects to the phone via bluetooth and monitors the current battery level. When the battery level reaches a configured percentage, it switches off the charging. At about 35 euro, it seemed a bit expensive for what I wanted.

After some more research, I discovered Personal Automation / Shortcuts. It is possible to create an automation that is triggered when the charge level crosses a threshold. Already owning several Tapo Smart Plugs I discovered that if the Tapo app is installed, an automation action can turn on or off a Tapo plug. So if you plug your charger into the smart plug, you can stop charging at whatever percentage you like.

Assuming you already have the Tapo app installed and your smart plug configured, goto the Shortcuts App and select Automation from the bottom middle. Click the + symbol to create a new automation and select Create Personal Automation. Find "Battery Level" and select "Rises Above" and set your desired percentage. On the next screen, click "Add Action", goto the Apps tab. Find the Tapo app, Turn on/off a device and pick the plug you want to use.

After creating the automation, edit it, and deselect "Ask Before Running" so it runs automatically. Now your charger should switch off when the automation runs!

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