Compared to my aging iPhone 7, the battery life is great. I would unmount the mounts that would eventually attach to the chopped ends of the crossbars since screwing with these on top of the car could be very difficult. Fits well, very comfortable, and great quality. FIRST. They fit my son perfect and he loves Dino print on them. After using it for an hour, the back of my ear had a deep divot in it. I did it by myself with plenty of clamps, but a friend might have made it a lot easier. no grommet?. After a couple days of using these headphones, I did leave a 4-star review, which I think is more than fair given that I identified a number of issues. Well, Maxell, I used to LOVE your products; now, you have lost a customer for LIFE.