SAE J1798 - Battery Design

Recommended Practice for Performance Rating of Electric Vehicle Battery Modules

SAE J1798 provides standardised test procedures for rating the performance of battery modules used in electric vehicle applications. It defines the methods for measuring and reporting peak power, available energy, charge acceptance, and efficiency — enabling consistent performance comparison between module designs from different manufacturers.

Published by: SAE International
Current edition: SAE J1798:1997 (reaffirmed)
Related standard: SAE J1797 (module packaging), SAE J2288 (life cycle testing)

Scope

SAE J1798 applies to battery modules in EV applications at the module level (not cell or pack level). It provides a common language for performance characterisation, supporting vehicle integration decisions and supplier comparisons. Test conditions cover a range of temperatures and state-of-charge operating windows.

Key Test Procedures

Peak Power and Energy Rating

Peak discharge and charge power are measured at defined pulse durations (2 s, 10 s, 30 s) at multiple states of charge. Available energy is measured at the USABC simplified discharge profile rate. Results are reported at both 25 °C and low temperature to characterise cold-weather performance.

Charge Acceptance and Efficiency

Charge acceptance tests measure the current a module will accept during regenerative braking pulses at various SOC levels. Round-trip energy efficiency is calculated from paired charge/discharge cycles using a standard test profile.

Disclaimer: This is not a definitive guide, just an indication and it is important that you always go back to the source for legislation.