Set battery charge limit for MacBooks.
This app modifies a parameter called BCLM (presumably "Battery Charge Level Max") in the SMC which limits the charge of the battery to a set value.
The source code can be viewed by opening src/Charge Limiter.app in Apple's Script Editor. It is written in Javascript Application Scripting (or JXA).
The companion smcutil binary (located under src/Charge Limiter.app/Contents/Resources) was copied from this repository. The source code for smcutil is also available there.
Download the latest version from the releases page.
The app is not code signed so you need to right-click on the app and select "Open" to bypass Gatekeeper's warning.
If you wish to undo the changes, set the charge limit to "100". The app itself does not install anything so if you do not need it anymore you can safely move it to the trash.
This app will automatically check and notify you for any updates when you run it.