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I threw together a current meter based on the content posted here . It consists on essentially 3 components soldered on a perf board. The 3 components are: ESP-12E LTC-4150 0.96" OLED module SSD1306 (128x64) Here it is, hot-glued into a simple 3D-printed enclosure, and running: The schematic is as follows: The meter is powered by the micro-USB port on the ESP-12E. I soldered header pins onto the IN and OUT terminals of the LTC-4150. The whole idea is that one could plug the source battery into the IN terminals, and plug the circuit to be tested into the OUT terminals, press the "Reset" (RST) button on the ESP-12E, and it will start measuring the average current draw of the circuit. The current meter can be easily tested with a passive load like a 100ohm resister, which will simply display a constant current value (V/R).  But it is really more useful for testing a variable load, like the ESPCLOCK , where running the current met...

This is an adapter for Ozito 18V battery trimmer (and possibly some Bosch trimmers as well) that uses a plastic blade for cutting. It lets you insert a 2.4mm trimmer line (about 8cm long) and use that for cutting. Simply cut a length of trimmer line and briefly heat up one end with a lighter so that a little bulb is formed. Then insert the trimmer line into the adapter and slot that into the trimmer as per normal. Make sure the trimmer line is not so long that it touches the safety guard. If that is the case, simply trim off any excess with a cutter or scissors. This part is best printed using PETG, which is a tougher and more flexible material. PLA is more rigid and breaks more easily. However, even with PETG, it will still break when it hits something really hard. Since this takes only 0.5m of material and 15 minutes to print, I will usually print a batch of nine at a time at very little cost. The blades that they sell do not break when it hits a hard object, but ...

Well, you don't really 3D print the entire battery tester. That would be neat though. This is a actually a 3D-printed casing for the  ZB206 battery capacity tester . What you do print is an integrated battery holder (rubber-band-powered) that can hold an AAA, AA or 18650 battery for testing. So it is easy to pop in any of those batteries and begin testing its capacity immediately. The ZB206 is mounted to the casing using 4 M3 x 6mm screws. There are 4 bolts that come with the board. I repurposed 2 of them as battery terminals, as shown in the photo. You can find the OpenSCAD source file and STL file on Thingiverse .  ZB206 usage instructions: If battery meter beeps on power on, press the [SK] button. Press [SK-] and [SK+] buttons to set the discharge current. For NiMH AA batteries, use ~0.5A. For 18650 cells, you can go as high as 1.5A depending on the cell condition. Press [SK] button to start the testing process. When the battery meter beeps. th...