Works, but annoying popup
You can see the voltages nicely. However, there are two major downsides. Every time I open the app, it tried to force me to allow the app access to my location. I have to deny it every time. This is quite annoying. When you are trying to monitor the battery voltage, you want to look at the past data. Unfortunately you cannot get a better resolution than a full day. To really understand battery charging etc, you would need to be able to zoom in. This is not possible though. If both of these issues were resolved, if give 5 stars.