Useful for testing unknown batteries, or as an external pack monitor

Bill of materials:

• GWUNW OLED Parameter tester (100V, 10A): https://www.aliexpress.com/item/32844522748.html
• XL7015 high voltage module (square-type, green PCB): https://www.aliexpress.com/wholesale?catId=0&origin=y&SearchText=XL7015+
• 26AWG wires, color coded
• Optional enclosure 64x58x35mm (Gainta G302 or equivalent)

Unpack and connect XL7015 module input side to CC limited power supply, set to 12V. Be careful, it's very easy to destroy it.
Then, connect your voltmeter on the output, and adjust potentiometer for 5V output.

Once set, hotglue it onto the display unit as shown. Wire it up following the wiring diagram below, or the supplementary photo.

Cut a 45x16mm rectangle hole into the front lid (using a dremel cutter and chisel for example), then slide in the assembly until it clicks together.