Review on 🔋 Versatile 4-in-1 Board UPS: Efficient Raspberry Pi 18650 Battery Charger, 3.7V to 5V 12V Conversion, Built-in Protection (5V 15W Output) by Justin Buck

most reviews are not related to this product. Even so, they don't output exactly 5 volts. I bought 2, one at 4.75v and the other at 4.95v. For most things it doesn't matter, but for a Raspberry Pi it will complain when it boots to low voltage (vcgencmd get_throttled). The good thing is that the seller will show you what resistor is used to replace it. I used a 100k trimmer set at 31k and got 5.15 volts from it. I booted my raspberry pi with external USB wifi and it ran for 3 hours 38 minutes. Then I checked sending a 30GB file and it was 2 hours and 22 minutes long. The Raspberry PI never lost power by unplugging the power supply. It was outputting 5.15V at the UPS terminals until it shut down. both batteries measured a bottom line of 2.77 V. if you don't mind playing around with it. These seem to be pretty good devices.