Choosing a USB cable that actually charges
Most cheap USB cables are wired for data first and current second. The conductor gauge is the thing that matters: a 28AWG power pair will sag under 2 A no matter what the packaging claims.
A quick test
Put an inline meter between the pack and the board and watch the voltage while the radio transmits. Anything below 4.7 V at the board is the cable, not the battery.
