I used these two batteries with my Sony A7 intensively for two weeks without any problems. I have not been able to make real comparisons with the official battery whose charging time is laughable in any event with this device, but it did not seem to me to last a much shorter time. The external charger is just essential, knowing that charge a battery on the camera or via the charger takes minimum 3 hours, it is very convenient to charge an extra battery simultaneously.