abstract = "This paper proposes a novel methodology based on the
Genetic Programming (GP) to derive behavioural models
describing the transient evolution of the terminal
voltage of a battery. These models analytically relate
the battery voltage to its state of charge,
charge/discharge rate, and temperature. Compared to the
popular equivalent circuit-based models, one of the
main advantages is the significant reduction of the
effort to produce the experimental dataset required to
identify the model parameters. The GP generates a
family of optimal 'candidate' analytical models, each
associated with suitable metrics that quantify
performance indicators like simplicity and accuracy.
The methodology is applied to describe the transient
discharge phase of a Lithium Iron Phosphate (LiFePO4 or
LFP) battery under realistic operating conditions,
considering the state-of-charge between 20percent and
80percent, discharge rates comprised between 0.25C and
1C, and temperature ranging from 5degreeC to 35degreeC.
The GP provides different solutions that can be chosen
by imposing the desired trade-off between accuracy and
simplicity. Two models are selected and validated
against experimental results. The chosen models
guarantee a quite low level of the relative root mean
square error (maximum 0.31percent and 0.22percent,
respectively) over the range of analysis.",