Let's dig in on battery, which is better on a few fronts. You can use the new Ray-Bans for up to eight hours on a single charge, which is twice the four-hour battery life of the previous generation. The charging case can charge the glasses to 50 percent in 20 minutes - a slight improvement over the 22 minutes to 50 percent for the first generation. The case for the Gen 2 glasses offers an additional 48 hours of battery life, up from 32 hours.