The invention is a charge state evaluation method and
system of a power
lithium ion battery. According to the method, step one is to establish a circuit model of an equivalent battery. Charging and discharging and standing experiments are performed on the battery, and timing sampling is performed so that a
voltage time curve is obtained.
Model parameters are identified via a formula so that a non-
linear relation between an open-circuit
voltage OCV and an SoC is obtained. Step two is to obtain an optical
estimation value of the SoC by matrixes of
state prediction, prediction error variance, filtering
gain, state
estimation,
estimation error variance, etc., according to
Kalman algorithm. According to the
system, an analog /
digital converter, a program storage device, a programmable storage device, a
timer and a displayer are respectively connected with a
microprocessor. A
current sensor and a
voltage sensor are respectively connected in a circuit formed by connecting the battery to be tested and a load, and outputs of the
current sensor and the
voltage sensor are accessed into the analog /
digital converter. The programmable storage device stores battery
model parameters obtained by the experiments. The program storage device stores estimation program of the method.
Estimation precision of the SoC can reach 1%, and the charge state evaluation method and
system is more stable; besides, the system provides estimation values of the SoC in real time.