In the beginning, USB could deliver up to 500mA of power at 5V, which worked out well enough for early phones. But as chipsets became faster and screens grew bigger, batteries ballooned in size (we covered the growth of battery capacity in a previous article). Today we'll focus on charging technology as there are quite a few competing standards. To keep things (relatively) short, we'll only cover the popular wired standards. USB As we already mentioned, the early USB standards had provisions for up to 2.5W of power, which was bumped up to 4.5W with USB 3.0. That's the official...
Source: https://www.gsmarena.com/counterclockwise_a_brief_look_at_past_and_present_fast_charging_technologies-news-35326.php
