I bought two pieces directly. Photo trip to London was announced. Each battery power in the 8 degrees Celsius outside temperature 650-800 shots. In "Home" -Use or rather to events where it is warmer, one made even more. I was so far no performance degradation after repeated use ie notice charging and discharging cycles. Tip my hand in cold weather. Heat pack or heating pad in a lens case, battery case and already there are no problems in cold weather.
