So a few months ago, I stumbled upon a thing at Adafruit.com called a "Charger Doctor" which was really just a Multimeter designed to slip inline with your USB cable. It was $7.50 and I liked it.

We may receive a commission on purchases made from links. One tool you'll find stashed in all the best electrician's tool backpacks is a multimeter. Most modern multimeters are of the digital variety, ...