As the electric vehicle industry continues to evolve, one of its focus areas is stranded energy. Stranded energy refers to the residual charge or stored energy left in a battery after an automobile accident that cannot be directly accessed but still poses a potential shock or fire hazard.
While several potential solutions exist for stranded energy, there is no standardized method for discharging damaged or used batteries, according to Rich Byczek, Global Technical Lead, Electric Vehicle & Energy Storage, Intertek. NHTSA (U.S. National Highway Traffic Safety Administration), NFPA (National Fire Protection Association), and SAE International are all working to address this gap.
The SAE Battery Standards Fuel Gauge Committee is currently developing SAE J3009: Stranded Energy – Reporting and Extraction from Vehicle Electrochemical Storage Systems. In addition, the SAE Battery Field Discharge and Disconnect Committee is working to develop a standard method and interface for the field discharge of live batteries.
A global testing and certification company with an expert on ANSI (the American National Standards Institute) Electric Vehicle Standards Panel (EVSP), Intertek is at the forefront of stranded energy standard development and testing.
The development of such standards is critical for several reasons, said Byczek. “Without diagnostic capabilities, the state of the battery is unknown. Charge left in a battery after an automobile accident poses great risk to secondary responders including tow truck operators, dealerships and vehicle repair shops. These responders need to have a standardized protocol for accessing the internals of the battery and safely discharging it.”
Currently, he said, there are two potential solutions for dealing with stranded energy. The “suitcase tester” combines the efforts of both the NHTSA and SAE committees. This solution would require all automakers to accept a standardized battery high voltage (HV) port that could be accessed by a single discharge tool. All tow truck operators would be able to use this tool to examine the status of the battery and remove stranded energy before proceeding with vehicle towing.
The second potential solution is an automatic self-discharge system. In the event of an automobile accident and the automatic disconnection of the vehicle's HV system, the battery would automatically self-discharge.
“Neither of these solutions is without issue,” said Byczek, “but both are an important step toward a standardized stranded energy solution. As members of the EV industry continue to work toward ensuring the safety of secondary responders, EV manufacturers must prepare for a new wave of standards and the new testing and certification requirements that accompany them.”