Simple to use auto zero every time you stop pedalling for 3 seconds or more your power2max re zeros no need to re zero manually no cadence magnet needed you dont need to install a cadence magnet on your bike your power2max calculates cadence precisely using its internal accelerometer battery change when the time come to change your battery after 300 to 400 hours of use 6 000 to 12 000km you can do it yourself plusmn2 precision power2max power meters deliver state of the art