Depends which one you get. Ive got one of these that is 2x AA batteries. Bikesconnect - Product Details | PZ Racing GPS Laptimer Start Evo | PZ Racing | Lap Timers | Bikesconnect Pty Ltd
I have 2 Aim solo's(well 1 DL and 1 standard),either can be used standalone or wired into your electrics.they last a good few days without needing charging.