This is simply a battery holder for charging CR123A-sized 16x340mm 3.7V Lithium Batteries using the commonly available TP4056 charging boards (ebay etc.).The batteries that I got from ebay for 1 dollar a piece promised 1000mAh of capacity. Yeah, sure! After testing them throughout some charge-discharge cycles the capacity turned out to be only about 300mah. To safely charge these batteries you therefore need to replace the current set resistor on the board since it is set to 1 A by default. I chose a value ok 3.9k (a 0603 SMT resistor) which gives me a charge current of roughly 300mA. Refer to the TP4056 datasheet for the handy resistor-current table. This makes charging via USB port possible as well since it's well below the max. 500mA. This was my first ABS print. Turned out ok.