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Wednesday, February 22, 2023

Review: 2 USB current measuring devices

 When you buy a charger or power bank, it usually brags about how much power it supplies. But how do you verify that it actually provides that power? The answer is that you have to use a device that measures current through the wire. Pierre Morrels suggested the Eversame tester, while Nelson Minar suggested  the mcdodo cable. To be honest, the mcdodo cable looked way easier to use, but I bought both to try. Indeed, the mcdodo cable has a very nice display to tell you how much power you're drawing from the cable. The eversame is bulkier and harder to use. I tried them both on the Pixel Stand 2. The geek in me loves the more detailed output from the Eversame --- it displays both voltage and current, and I get a kick out of seeing the Pixel Stand 2 draw 19V and 1.5 amps when the phone's battery is nearly empty for a full 21W of power to the phone (minus a 7W penalty for supplying power wirelessly), and then dropping down to 9.5V and 0.7amps past 50% charge, and then finally all the way down to 5V.

What got me to return the mcdodo cable, however, was that I noticed that the Pixel Stand would occasionally stop charging for no reason with this cable. There might be something in the cable that interferes with the power negotiating process. After a while, it would flip back to normal and display 18, 27, or 21W depending on the mood of the Pixel Stand 2.

The Eversame also provides a way to store the capacity of the current passing through so you can test how far gone your battery bank is. That's a useful function, so worth the higher price and bulk. I'm keeping it.

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