Stress testing of individual CERENERGY ABS60 battery cells by Altech Batteries’ (ASX: ATC) joint venture partner Fraunhofer IKTS has proven the technology to be safe under extreme conditions beyond standard operating parameters.

The company developed a rigorous testing protocol in accordance with international standards to evaluate the cells’ performance under abnormal or stressed conditions.

The various tests aimed to verify the performance, integrity and resilience of each CERENERGY cell and have delivered “excellent results” with regard to safety and operational robustness.

Risk evaluation

Altech managing director Iggy Tan said the tests were crucial for evaluating potential risks, mismanagement or external factors.

“Expert testing by Fraunhofer has validated the robustness of CERENERGY technology and showed the cells continued to operate for days or even weeks under extreme conditions that would cause typical lithium-ion cells to fail,” he said.

“CERENERGY batteries have proven to be safe under all conditions, ensuring uninterrupted operation without risk or performance degradation, even in the event of individual cell failure.”

Discharge tests

Fraunhofer conducted daily charge and discharge cycling of each CERENERGY battery cell at 300° Celsius with a state of charge (SoC) range of between 20% and 100%.

All cells reportedly passed both undercharge (less than 1.7 volts) and overcharge (more than 10V for 15 hours, or four times higher than the nominal voltage) tests, demonstrating the technology’s robustness, effective integrated safety features and strong resistance to damage.

Fraunhofer also performed a successful cell short-circuit test at 100% SoC with a discharge to 0.2V, during which time the current reached up to 120 amperes.

C-rate regimes

Fraunhofer tested the cells across a range of C-rate regimes — which refer to a battery’s charging and discharging capabilities, measured as a multiple of its capacity — under extreme temperature conditions and significantly above the typical operating temperature of below 300°C.

The company recorded no failures during these tests, demonstrating the robustness of the CERENERGY battery cells even under severe conditions.

Fraunhofer has scheduled higher C-rate testing as part of the ongoing test regime to further evaluate and define the physical performance limits of the cells.

Thermal testing

The company conducted thermal stability testing under overheating conditions to evaluate the upper limits of the CERENERGY battery’s operating temperature range.

Cells were initially cycled at a C/8 rate of up to 400°C — or 50°C above the maximum expected operating temperature — and additional cells are showing stable and consistent performance at C/8 and 350°C.

Testing is ongoing, with cells being cycled at C/8 between 20% and 100% SoC at 300°C.

Cell failure assessment

Individual cell failure testing assessed whether one or more cell failures would disrupt electrical current flow.

This test is critical to evaluating the real-world performance and reliability of the batteries, with the results demonstrating that cell failure does not negatively impact overall system performance.

The CERENERGY battery continued to operate safely and reliably during the tests, maintaining functionality and continuous operation without significant risk or performance degradation, even when individual cells failed.