With the included charging cable (USB-A to Micro-USB) for Byron wireless or the included charging cradle (USB-A to charging contacts on the earphone itself) for the Byron BTA you can charge both earphones on any usual USB power supply or USB port (e.g. on a computer). It doesn't play a role, whether the USB connection is High Powered or Low Powered.
A complete charge takes approx. 2:00 h for the Byron wireless and 1:30 h for the Byron BTA, but already after half an hour of charging more than half of battery runtime is available again.