USB power bank, using 2x18650 Li-ion batterys

thingiverse

Power bank utilizing a cigarette lighter type USB charger. Two versions exist: round and more bulky, with identical dimensions elsewhere. Added variations feature an external 5mm LED hole. Required components: - A plastic battery storage case box holder for two 18650 batteries - A rocker switch measuring 9x13 (smaller size) - A suitable USB charger equipped with a built-in LED, as seen in the images Regrettably, it's difficult to determine what constitutes an effective solution. Most chargers of this type contain basic regulators and can be used safely with under-voltage sources; however, it's essential to ensure the source voltage is at least 1.5V higher than the output (5V). Connecting wires should be a straightforward task: simply solder them directly to the charger's metal contacts without any unnecessary complexity, and remember to connect the switch to complete the circuit. Alternatively, one can disassemble a car charger and repurpose the USB connector with LED, then solder a 7805 regulator directly to the connector for a functional solution. A desirable enhancement would be to locate a display that shows remaining power levels. It would be highly beneficial to have a display indicating 0-100% power capacity, connected behind a push button for quick reading. Currently, I am searching for an appropriate measurement display. If you're unsure about what you're doing, it's best not to proceed with the project.