A $10 USB Multimeter for testing cellphones and powerbanks

This PowerJive USB Multimeter measures amps, volts and mAh on all my portable devices.

I wanted to know if my 3 year old 10,000 mAh USB powerbank was still holding anything close to 10,000 mAh. This USB multimeter does exactly what I am looking for. The meter sits in-line between your charging source and whatever device you seek to charge. Simply plugging the dongle in turns it on. The device immediately displays volts and charging amps.

To test capacity of a battery first you need to drain it completely. Reset the meter by plugging in the powered side, and then holding in the units only button for a few seconds. The mAh meter will zero out, and you can plug in whatever you want to charge up. When the device reaches 100% charge, the mAh meter will tell you approximately what your capacity is, at that charging rate.

My 3 year old 10,000 mAh powerbank, that has seen several hundred cycles, still has about 82% of its charge.

PowerJive USB Voltage/Amps Power Meter Tester Multimeter, Test speed of chargers, cables, capacity of power banks via Amazon