I have a collection of batteries I find cycling. Yesterday it was a Galaxy Note 4. You don't have to cycle thousands of km to find a mangled PDA wit h the dislodged battery nearby. They leave the phone on the roof to load s omething into the car which requires both hands. The phone must absorb mos t of the 120 km/hr oblique impact because more often than not, the dinged b attery is still serviceable, at least as a bike light.
They need to sell $0.79 clip-on LEDs on Ebay [free shipping] letting cyclis ts find their own batteries. Just 2 small alligator clips, the LED, a Si r ubber strap and maybe a switch. If some kid steals your dorky looking bike light when you are inside shopping, it's no big deal. You are only out of $0.79.
Bret Cahill