bat-perf is a battery performance model appropriate for conceptual design and performance studies of aircraft. It is a very simple approach, but it captures the required nuance for this purpose.
The ideas implemented in this model were first published by this author in a series of LinkedIn articles titled Batteries Are Not Fuel from September 7 to October 18, 2022.
Formalism underpinning these ideas was recently published by this author as an AIAA Paper.