USB tester.

USB power tester

This cheap USB power tester is a great little inline device for monitoring volt (V), amps (A), milli amp hours (mAh) and duration of current-on-time .

Introduction

For some time as backyard tinkerer (Or more like a bathroom tinkerer, in my case) I have struggled to find a simple way of measuring the run time that a laptop fan gets from a 18650 battery-powered power pack. I use these batteries for my USB blower fans for my range of powerful stick burning Blower Stoves for lightweight backpacking camping.

Large C-Ring Blower Stove with a single cooking position. The Blower air tube has a bend in it that allows the blower and power supply to be angled back and away from the flame. The USB power tester will make the estimation of battery run time easy.
Large C-Ring Blower Stove with a single cooking position. The Blower air tube has a bend in it that allows the blower and power supply to be angled back and away from the flame. The USB power tester will make the estimation of battery run time easy.

I found out about these Keweisi devices from Steve’s theultralighthiker blog post. Mine is very similar and is called a USB Tester. My USB power tester has just arrived and at about AUD 6.00 including shipping, it is great value and a very nice instrument that is easy to connect into a USB circuit.

It measures and clearly displays volt (V), amps (A), milli amp hours (mAh) and importantly for me, it holds the recorded time for which the current was flowing when the power pack cuts out.

It has only one control button. “Good for me as I usually just find the ‘bloke-button’ on a Microwave oven and just keep using it.” The simple resets button just clears the time recording and the mAh when required.

USB power tester placed inline between a 18650 battery powered power pack and a laptop fan that is used as a fire blower in an ultralight blower stove for backpacking camping.
USB power tester placed inline between a 18650 battery powered power pack and a laptop fan that is used as a fire blower in an ultralight blower stove for backpacking camping.

Recording battery run time with the USB power tester

Timing the run-time from my 18650 batteries running my blower fans with the device was easy. All I need to do is plug the USB power tester in between the power pack and the fan an press the reset button. When the power runs out and the fan stops the device stores both the run time and the total mAh of energy used. The saved values are displayed when the USB power tester is energised once more.

Here us a little Instagram video of the USB power tester working.

Conclusion about the USB power tester

Although I am not sure about the accuracy of the voltage and current readings, they seem to agree with my best measurement made with a medium quality multimeter. The timer seemed to be Ok when checked against a clock on my PC, so it looks like a simple solution to my mHh and runtime recording.

Addendum

If anyone knows of a similar device that will switch the 5V power on and off automatically with a variable frequency, without using much power, please would you let me know about its source (Please use the comment section or contact form).

Tim

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