Once you open any App on the Karoo, it will be running in the background once you return back to the Home Screen. This means that it will be using up some battery even if your unit is idle. You can force close apps every now and then to keep your Karoo responding fast and being battery efficient.
Double press the bottom right (E) button.
Swipe an app to either side or tap on the "✕" to force close it.