A good multimeter (or a few of them) is an essential part of anyone’s electronics workbench. The only thing more useful than a multimeter is a logging multimeter that can take recordings over time.

Here is a Simple LED Volt meter to Monitor the charge level in Lead Acid Battery or Tubular battery. The terminal voltage of the battery is indicated through a four level LED indicators. The nominal ...

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.