HFT Ammo Box UPS/18650 Battery Pack

thingiverse

I built a 3D print design that supports a 3S16P 18650 battery module, which I'm using as a 12V UPS for essential household equipment. The module is housed inside an Ammo Box from Harbour Freight Tools and includes three packs of 16 18650 batteries, totaling 48 batteries with 4Ah each rating. This configuration should provide 192Ah for the module. Each pack consists of four batteries arranged in a 4x4 grid, with fusible links soldered to the positive end of each battery. The charger input is connected to a buck/boost converter that accepts voltages from 5V to 30V. The output includes a 12V power port and two 5V USB ports for charging devices. The voltage regulator is programmable, requiring a setting of 12.4V for the Battery Management System (BMS) on the battery pack. Several choices of wall warts can be used to charge the system, so I won't list specific options in the parts list. You'll need to select your own and set the charger's voltage and current settings accordingly. Since the input voltage is variable, a solar charger can also be used as long as it doesn't exceed 30V. The wall wart I use provides 12VDC at 2A, so I've set the buck/boost converter to charge the battery at 12V/1.5A. The hardware supports higher loads, but since I only use up to 3A when the battery pack is in operation, standard 2.1mm power connectors are sufficient internally. Caution: When soldering the fusible wires and connecting the packs together, remember that the batteries are live and can cause shorts if not handled properly. Cover all exposed wires with tape except for the specific ones you're working on. Also, ensure that the cells within a pack have similar characteristics to avoid any issues during operation. Caution: When assembling the battery packs, make sure they're matched together with similar characteristics. Test them with a volt meter before connecting them in series. I used 18650 batteries available anywhere and got mine brand new on eBay. To assemble the module, you'll need the following parts: * Ammo box - Available from Harbour Freight Tools * 18650 batteries - Available anywhere * 14 guage wire - Available from any electrical supply store * Fuse Wire - Available from Amazon * Nickel Strip - Available from Amazon * 3mm Nuts Bolts Washers - Available from Amazon * Buck/Boost Voltage Converter - Available from Amazon * 3S Battery Management System - Available from Amazon * 12V Power Port and USB power - Available from Amazon * Power Connectors - Available from Amazon * Panel mount power connector - Available from Amazon The 3D print items required for this project are: * 18650Cap.stl (6 required, 3 black, 3 red) * BatteryPackSledSimple.stl (2 required) * BatteryPackSledWithBMS.stl (2 required) * ChargerMountPlate.stl (1 required) * PackRetainerCrossBar.stl (2 required) * PackSpringRetainer.stl (1 required) Each part can be printed in PLA, except for the 18650 Caps which should be 3 black and 3 red. The PackRetainerCrossBar should be printed upside down without supports, while supports are needed for BatteryPackSledWithBMS, ChargerMountPlate, and PackSpringRetainer.