There are several existing standards and guidelines that may be applicable to the testing of these batteries.
One option is to follow the UL 2580 standard, which outlines requirements for the safety of lithium ion batteries. This standard includes requirements for the design, construction, and performance of lithium ion batteries, as well as requirements for the testing of these batteries to ensure their safety.
Another option is to follow the guidelines provided by the International Electrotechnical Commission (IEC). The IEC has published several standards related to the testing and evaluation of lithium ion batteries, including IEC 62660-1, which covers the safety of lithium ion batteries, and IEC 62660-2, which covers the performance and endurance of lithium ion batteries.
It's worth noting that these standards are not specifically designed for the testing of large batteries used in electric vehicles, but they do provide a good starting point for ensuring the safety and performance of these batteries. It may also be necessary to consult with industry experts and conduct additional testing to ensure the safety and reliability of these batteries in the specific application of use in electric vehicles.