Just to keep you posted, I'm using the SJCam -4000 model, black, at 720 resolution by 30 fps, getting about two hours and twenty minutes of recording, on a 16 GB SD card...

The SJ400 can be charged while it is in use, so says the instruction manual, but in reality, the cord can NOT get through the waterproof case... I have a 12 volt/12 ah rechargeable battery for my lights, so I could in theory run the camera off of that supply... maybe I'll get a second camera, install the USB port on my bike, and charge one while the other is in use... Maybe I'll drill a hole in the waterproof case...

I have 12v LED lights, I have to install a dual USB port soon, on the 3 bikes that have 12 volt lights...Marinco SeaLink Deluxe Dual USB Charger Receptacle - Star Marine Depot