Final check Custom 2S 18650 Battery Pack with BMS & 5V Buck for a Festival Totem (EasyEDA)
Good day everyone,
My daughter and I are building a custom festival totem pole and ran into a classic problem: commercial power banks keep shutting off on us because the Arduino Nano’s idle current draw is too low to trigger their "stay alive" circuit.
To fix this, we've designed a custom PCB that stays on until we hit the physical power switch. It uses two 18650 batteries in series (7.2V nominal) stepped down to 5V via a buck converter, managed by an onboard BMS.
It passes DRC in EasyEDA perfectly, but as we all know, DRC won't catch engineering or schematic logic errors! We are ready to get this manufactured but would love a quick sanity check on our layout and schematic first.
BAT1 & BAT2: 18650 Battery Holders. Wired in series to combine their voltage into a stronger 7.2V main line, giving the system more efficiency and headroom to run smoothly.
U3: 5V Buck Converter. Steps down that 7.2V battery power to a stable 5.0V, which is the exact voltage needed to safely power your Arduino Nano and WS2812B LED strips on the totem pole.
L1: Power Inductor. Works with U3 to filter, smooth out, and efficiently convert the electricity as it steps down.
C1, C2, C3: Filter Capacitors. Local power reservoirs that absorb electrical spikes and keep the 5V line perfectly stable so your LEDs don't flicker.
U1: Battery Protection IC. The safety brain that constantly monitors the battery voltage and current to prevent over-discharging or dangerous shorts.
Q1 & Q2: Dual MOSFETs. High-current electronic switches that U1 can instantly slam shut to cut off power if a short circuit happens anywhere on the totem.
U4: Decoupling Capacitor. Cleans up electrical noise right at the safety chip (U1) so it gets clean, accurate battery readings.
R4: Sense Resistor. Measures the exact amount of current flowing through the circuit so the protection system knows if the LEDs are drawing too much power.
Pins 4 & 5: Microcontroller Headers. Delivers the clean, regulated 5V power straight to your Arduino Nano to keep it running.
CN1 to CN6: LED Output Connectors. Dedicated physical solder ports to cleanly split and distribute the 5V power and data signals out to the individual LED strips up the pole.
