3 x D Cell to 1 x 18650 battery converter for flashlight

thingiverse

This is a part to convert the 3 x D cell batteries of a large flashlight to run off one LiPo battery. Voltages should be compatible. 3xD = 3 to 4.5V. 1 18650 = 3 to 4.2 V. This includes no overvoltage, undervoltage, BMS, or current protection so caution is advised and use at your own risk. Consider adding such features to your circuitry. To Print: I used an Elegoo mars SLA printer. You may need to increase the maximum print height in your machine configuration files. A large footprint/raft with supports is necessary as this is a tall heavy part with a 13 hour print time. To use print the part in the highest resolution possible. Strip 18 guage bare copper stranded wire and thread through the holes, joining on the bottom side - twist tight and solder in place. Fold the joint over to form the positive pole of the battery. Inside the tube insert the 18650 positive pole - the button should contact the wire you threaded through the part, completing the circuit. Put inside your flashlight and enjoy a lighter flashlight without the issues that come with alkaline batteries.