> čia kame negalima keist baterijos?

Šituose:
http://www.polar.com/en/products/accessories/CS_cadence_sensor_WIND
http://www.polar.com/en/products/accessories/CS_Speed_Sensor_WIND_and_Universal_Bike_Mount_Set

Iš naudojimo vadovo :) : "The battery cannot be replaced. The sensor is 
sealed in order to maximize mechanical longevity and reliability. To 
purchase a new sensor contact your authorized Polar Service Center or 
retailer."