How to fix a Baofeng USB charger that doesn't charge.
If your Baofeng USB charger base never goes green to indicate the battery has reached full charge, this may apply to you. Another indication of the problem is the LED stays solid red with no battery inserted, it should flash alternate red/green. I recently bought a Baofeng which was supplied with a USB charger which is convenient but even when I forgot to unplug it one night and left it on for 2 days it never showed 'green' and checking with a multimeter showed the battery was still under 8V (*never* leave Li-Ion cells/batteries charging unattended.) Turns out the USB cable has a built in boost converter to bump up the 5V to something high enough to charge a 2S 7.4V pack. Unfortunately the boost converter in my USB cable only bumped it up to 9.2V and the reverse polarity protection diode (circled red) in the charger base was wasting 0.8V of that so there's no chance it would ever reach charge termination voltage of 8.4V A quick google showed the mains powered chargers com