Voidbox’s PwrTool 500 is a battery and power monitor for Home Assistant based on the company’s FLIP_C3 ESP32-C3 board with a 60V-tolerant buck converter that is designed for off-grid and other DC-powered applications.
The PwrTool 500 is designed for most 12-48V DC systems and is capable of handling up to a 500A peak current across a 6-60V DC range. The board supports ESPHome firmware for easy integration with Home Assistant, and provides data about your energy flow, generation, storage, and usage.
PwrTool 500 specifications:
- Main board – FLIP_C3 Controller Board
- Wireless Module – ESP32-C3-MINI-1
- SoC – ESP32-C3
- MCU – RISC-V core @ 160 MHz
- Wireless – Wi-Fi and BLE 5 connectivity
- PCB antenna
- SoC – ESP32-C3
- USB – USB-C port for firmware flashing and recovery
- Expansion
- Stemma QT and Qwiic connectors (I2C and UART)
- 9-pin + 10-pin headers with GPIO, I2C, SPI, PWM, UART, 5V,. 3.3V, and GND
- Misc
- Level-shifted WS2812 output, capable of powering 100+ LEDs
- Status LED
- Boot and Reset buttons
- Onboard 5V/2A buck converter – Up to 10W; tolerant up to 50V DC for direct connection; 60V absolute max (with pre-charge resistor)
- Wireless Module – ESP32-C3-MINI-1
- Misc – SHTC3 sensor for monitoring ambient temperature and humidity
- Power Monitoring
- System Voltage – 6–60 VDC (compatible with all lithium, LiFePO₄, and lead-acid batteries)
- Current – 500 A peak / 300 A continuous current shunt
- INA238 16-bit pre-amp & ADC with on-die temperature sensor facing shunt
- Polarity – Jumper-selectable hot- or cold-side monitoring (preset to cold)
- 45W N-channel MOSFET for PWM LED lighting control or high-power load control via relay or contactor
- Dimensions – TBD
The PwrTool 500 power monitor ships with a custom ESPHome firmware installed, and Voidbox provides a GitHub repository with various sample YAML configuration files for the FLIP_C3 and PowerTool 500, which you can use as is (e.g., pwrtool500.yaml) or customize to your needs. You’ll find more details in the wiki, including the links to the schematic, PCB layout, and BOM created in EasyEDA Pro.
Once connected to Wi-Fi, your PwrTool 500 should quickly appear in Home Assistant with power, voltage, current, temperature, and humidity data, as well as toggles for LEDs and the PwrTool MOSFET. While there are plenty of Home Assistant-compatible power monitoring solutions for AC devices, the PwrTool 500 targets DC-powered appliances.
VoidBox launched the PwrTool 500 battery and power monitor on Crowd Supply with a $5,000 funding target. A pledge of $149 should get you a PwrTool 500 with a 2-meter red 18 AWG wire with ferrule and ring terminal shipped by the end of April 2026. The price includes worldwide shipping.
Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.
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