Take a look at the settings in the home app. There is one to increase/decrease the overall sensitivity to events, and another to "record more" or something to that affect. It will eat more battery, but it will cause it to capture more pre-roll footage prior to triggered events. Unfortunately, even with it set to most sensitive, and maximum recording it at times not capture an entire event. If the car, person, animal, etc, doesn't keep moving, it will sometimes just cut off the event. It does a decent job most of the time, but it's definitely not perfect. I've found the actual object detection to be quite good overall. I rarely get false events, but sometimes rain or snow will generate false events at night.
With regard to it not being wired, I do believe it will turn down some of the settings by default to try to save battery, but you should be able to override those. If you're planning to keep it on battery, I would recommend that you create zones to trigger just on areas that are most important to you.
