Portable laboratory power supply (battery & AC) under the $20
thingiverse
Assuming you have old laptop power bricks and/or Ryobi battery to spare. XYS3590 is affordable buck converter up to 36V/5.1A -80W This box housing two laptop power bricks 16V&19.5V = 36.5V/4.5A connected serial. The power bricks' plastic covers are removed due size, cooling & allowing to connect the 2nd power brick's AC input internally, having just one AC cord. You can also place Ryobi One -battery. Under the battery there is a place for the micro-swich, which disconnects the power bricks feed, when the battery is inserted. Kudos to TeachingTech providing the Ryobi battery cradlle .step file via https://www.thingiverse.com/thing:4799791. Tip: Somebody noted that the XYZ3590 heatsink is installed with no thermal paste and screws are very loose, mine had the same. Just pull out the back PCB, two heatsink screws comes visible, add the thermal paste on two chips, screw it back together. This 'upgrade' reduced the unit's temperature 13C under the 13.8V/62W load (input 36.5V). The standard unit couldn't handle the same load with battery (18V) input but overheat protection (110C) kicked in, now it stays on 97C level.
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