In this quick tutorial/review, I'll be telling you about Battery Diag. Battery Diag is a free app for Mac that also serves as a widget for notification center. It shows your battery percentage and will also show you the time left on your battery. If you open the app in the menubar, it will display the health, cycles, and general state of your battery.
Battery Diag menubar window
Battery Diag notification center widget
Battery Diag also functions as a widget for your notification sidebar. Once added, the widget will show similar information to that of the menubar window, but also allow you to view the temperature, battery capacity, and more.
This app has been very helpful in informing me on the status of my battery. One of my favorite features of the app is that the menubar extension simply shows the battery percentage and not the battery icon unlike the default battery status for Mac. I've been using this app for a few months now and the only complaint I have is this: When your battery is about to die and requires a charger, there is no notification to let you know. As you can imagine this is very frustrating, so I emailed the developers at Rocky Sand Studio asking if this would be something they could add in the future. The support team soon got back to me saying that this is something they will definitely be adding and for now you can show the default battery status in order to receive a notification.