Fast charging of lithium titanate battery had been reported
in [7] and [8]. Therefore, a battery charger is vital to be
designed to efficiently charge the battery. Constant-current and
constant-voltage (CCCV) is a common charging strategy that
has been used for battery charging. The voltage of battery in
constant-current (CC) phase is increasing in nonlinear manner.
Therefore, an accurate battery model is vital for charger design
process so that the charger would give a proper charging power
to the battery. Simple mathematical model, which can be
represented in transfer function or state-space equation, is
usually more preferred in battery charger design because it can
be easily utilized for the control theory.