PwrTool 500 Integrates High DC Current and Battery Monitoring Into Home Assistant

Chloe Madison's Voidbox Industries (VDBX) is launching an open source shunt and battery monitor. PwrTool 500 monitors DC systems up to 60 volts and 500 amps. It can connect to existing microcontroller platforms or easily integrate into Home Assistant with VDBX's ESP32-based FLIP_C3 board.

Power shunts enable measuring current on power rails with very high currents. The measurement relies on knowing a piece of metal's very low resistance. By measuring the voltage drop, you can calculate the current and power of a DC system.

These shunt types monitor a single battery or a battery bank's condition and state of charge. For example, a power shunt can monitor the battery in a solar power installation. Since a dwelling powered by solar can benefit from automation, a shunt like PwrTool 500 provides a way to monitor and communicate the data to an automation system like Home Assistant.

Home Assistant is an open-source (software) project for home automation. One key feature is the ability to run 100% locally on a network, making it a non-cloud-based solution. It accepts data from sensors, like PwrTool 500, and lets users monitor, report, and create automation based on the readings.

VDBX chose a 16-bit high-precision Texas Instruments INA238 sensor for PwrTool 500. While this level of precision may only be necessary for some measurements or applications, it does offer a level of accuracy not commonly found in other shunts.

PwrTool 500 also offers flexibility in connectivity. It features two Qwiic / Stemma QT-compatible headers, allowing for daisy-chaining with other sensors or actuators in a monitoring system and interfacing with a wide range of microcontroller boards. Alternatively, it is compatible with FLIP_C3, also from VDBX.

The FLIP_C3 Controller board has an Espressif ESP32-C3 SoC containing a WiFi and a Bluetooth radio. PwrTool 500 has headers that align with the FLIP_C3, which supports supply voltages of up to 50 volts. The FLIP_C3 can run existing firmware like ESPHome, or you can develop code using Arduino or the Espressif IDF.

VDBX is incorporating several user-friendly features into the PwrTool 500. For instance, jumpers determine the polarity of the sense leads, allowing them to monitor the high (hot) side or low (cold) side of a circuit. Another feature is a MOSFET that can power loads up to 45 Watts, such as PWM LED lighting or an external contactor like a relay (solid state or electromechanical.) Additionally, the INA238's on-die temperature sensor faces toward the shunt so that it can help measure the shunt's temperature.

PwrTool 500 is an open source design with a CC4.0-BY-SA license. The EasyEDA schematic, PCB, and bill of materials are now available. VDBX plans to make 3D models available later.

Voidbox Industries is launching the project soon. To be notified when pre-orders become available, sign up for notifications on the PwrTool 500 Crowd Supply campaign page.