Almost everywhere I go I have my Garmin GPS with me – hiking, biking, or just driving around. And this thing eat batteries, so I use a lot of rechargeable ones.  Recently I got really tired of my attempts to keep track of which battery is full and which needs recharging, and which one doesn’t hold charge well and needs recycling, so I came up with this very simple battery tester.

It is nothing special, but it takes just a few hours to build and works just fine.

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