Mobile lab power supply

thingiverse

My neighbor handed me a malfunctioning battery from an ebike, which only had eight (or six? I've lost count) dead cells, and I decided to create a portable lab power supply with USB charging capabilities. It's configured as 6S7P with 18650 Li-Ion batteries, providing roughly 14Ah and 25.2V when fully charged. Inside, it's a bit cluttered, but it works flawlessly. The hardware consists of one DC-DC step-down regulator (LM2596) with an LED display, which shows the input voltage from the battery. A combined module for volt and ampere is soldered to the output, displaying the voltage at the banana plugs and the overall current being drained from the battery. Two simple DC-DC step-downs are installed, one for each USB plug. The XT-60 and MPX-plug are used for charging the 18650 batteries, with the MPX-plug serving as the balancing connector. A wiring diagram will follow later.