According to PS5: The Ultimate FAQ it takes approximately 3 hours to charge the Playstation 5 controller when the battery has no remaining charge. https://blog.playstation.com/2020/11/09/ps5-the-ultimate-faq/. This time is just one hour longer than the PS4 controller’s average charging time.
You can charge your PS5 controller most effective when the temperature is between 10 °C and 30 °C (50 °F and 86 °F). It’s recommended to charge the PS5 controller at least once a year to keep it functioning properly.