Limpkin's XT60 Parallelizer Board Safeguards High-Power Batteries Connected in Parallel
ATtiny microcontroller individually monitors four Li-ion batteries and disconnects the bank if it detects a fault.
Electronics geek Mathieu Stephan (Limpkin) addressed the challenge of safely connecting high-powered batteries in parallel with the XT60 Parallelizer board. This microcontroller-based solution monitors the current on each battery and acts swiftly after detecting a fault.
One critical concern with batteries in parallel is ensuring their voltages match before connecting them. Even the slightest voltage disparity can create a current imbalance, potentially overloading a battery and posing a fire hazard. The XT60 Parallelizer offers a reliable and safe solution to this problem by inhibiting the battery system from charging or discharging until a user addresses the fault.
Limpkin equipped the XT60 Parallelizer with a Microchip ATtiny806 microcontroller that monitors the current on each of the four batteries. It promptly turns off the (charge or) discharge port's solid-state relay and alerts the user upon detecting an imbalance. An audible alarm from the piezo buzzer and a message on the disconnected battery's high-contrast LCD panel lets the user know which battery to address.
Limpkin illustrates the operation with the simulated example of a BMS disconnecting one of the batteries during discharge due to overheating. The test setup includes four Li-ion batteries connected to the XT60. They power a DC to AC inverter connected to a 220 VAC lithium-ion battery charger. That charger connects to a spare battery. (To be clear, this battery is separate from the four connected to the XT60. No free energy attempts here!)
Each battery has a disconnect switch. In the video demo, Limpkin "disconnected" battery number three. The XT60 immediately disconnected its output and started beeping — just as designed.
While the XT60 is not currently available in the Stephen Electronics Tindie Store, you can download the ATtiny firmware, KiCad design files, and PCB gerbers from this GitHub repository. Check out Limpkin's detailed blog post for a deeper understanding of the board's design.