This is still a problem : > Finally, the USB Battery Charging spec enables a weirdly missing feature: a device plugged into a battery pack had no standard USB

This is still a problem : > Finally, the USB Battery Charging spec enables a weirdly missing feature: a device plugged into a battery pack had no standard USB command it could issue that simply asked, “How much current can I draw?” Instead, different manufacturers came up with solutions that were not always compatible, limiting charging among certain devices. It's not a proper power delivery standard until this issue is dealt with. (Note that this also applies to other unreliable power sources.) Heck, even to the main house power : you can only draw 240W so many times before you trigger the circuit breaker...