Abstract:
Lithium- ion batteries have higher energy density, low self-discharge, decent cycle life and
are eco-friendly. Because of these characteristics, they have been a widely used as
rechargeable battery in portable electronic devices, electric vehicles (EVs), grid energy
storage, and renewable energy. Several charging methods have been introduced in
literature with changed suggestions on charging time and life cycle. Most of these methods
use an open-loop approach while CT-CV is a closed-loop charging method which uses the
instantaneous cell voltage and current. Closed loop charging reduces the time that it takes
to charge a big capacity battery. When charging a smartphone, this approach keeps the
temperature constant while charging quickly. Existing Lithium-ion battery charging
methods lack detailed design and control circuits that use constant temperature and
constant voltage (CT-CV) in close-loop techniques. Our work addresses this gap by
explaining the circuit control and implementation of the CT-CV technique by employing a
feed-back proportional integral derivative (PID) controller with rectifier feeding the buck
converter. Voltage Mode Control (VMC) and Average Current Mode (ACM) control
methods are implemented to maintain the battery voltage, current and temperature at safe
limits. In this thesis, MATLAB Simulink is used for simulations. As per simulation results,
23% faster charging is achieved by implementing VMC and almost 50% faster charging is
attained by employing ACM technique in the PID controller. Moreover, a power factor of
unity is achieved as rectifier current and voltage waveforms are sinusoidal, which increases
the efficiency of the Li-ion battery. The results are verified by conducting experiment in
which the proposed method is compared with the reference battery and the most commonly
used CC-CV method. No technique has been implemented on the reference battery in order
to regulate its voltage and current. According to experimental results, the proposed
technique charges up to 25% faster than the reference battery and the CC-CV method.
