I have a couple of cheap cell phones that I use for playing with new (to me) apps so I won't inadvertently mess up the phone I use and need on a regular basis. There's a compass / GPS app that I want to try in my car driving to work tomorrow, so I pulled out burner phone #2 and installed the app. When I took the phone out of the box, it showed the battery status as 97%.
Not wanting to run it down while installing the app, I connected it to a charger and plugged it in, then installed the app and played with the configuration for a couple of minutes. Battery charge state was now down to 91%.
So I turned off the phone and left it for a while. Came back and it was at 86%. I was using a generic charging adapter from Amazon, so I switched to the one that came with the phone and tried again. Went down to 81%. So I ditched the adapters altogether and plugged the USB cord directly into my computer. Went down to 77%.
What's going on?