An Enhanced Dynamic Battery Model of Lead-Acid Batteries Using Manufacturers' Data

Modeling and simulation of lead acid batteries is of utmost importance for transportation systems such as hybrid and electric vehicles, golf carts, electric scooters, and wheelchairs; and for battery backup systems such as UPS for computers and telecommunication systems. Considerable effort is put into the selection of the appropriate battery with specific regard to the battery's State of Charge (SOC) and battery reserve time during the discharge profile for the various loading conditions expected. A previous technical paper presented a dynamic battery model by the same authors [1]. The new enhanced model has increased accuracy; it includes voltage, current, and power monitoring functions and further permits modeling of the cycle-by-cycle charge/discharge characteristics which is imperative for regenerative applications. Furthermore, the operating features of this enhanced battery model are demonstrated for two regenerative simulations. The new battery model is interfaced to a full-bridge, bi-directional, PWM controller with bi-polar voltage switching. The load is a dc motor model with motor parameters such as load torque, viscous torque and inertia. The power converter/dc motor system presents bi-directional power flow to the battery model. The purpose of the first simulation is to demonstrate real-world operation of the battery model including regeneration. A second simulation has an ultra-capacitor bank connected across the battery terminals to compare the battery model charge/discharge parameters such as voltage, current and power when the ultra-capacitor bank is absent and when present in the system.