experiment and modeling study on battery...

Experiment and Modeling Study on Battery

Performance

Shuang Dua, Ruijuan Guo

b, Shangyuan Sun

c

College of Engineering Technology, Jilin Agricultural University, Changchun City, Jilin

Province, China a [email protected], b [email protected], c [email protected]

Abstract. Battery is an important part of the electric vehicle energy storage

system. The performance parameters of battery are comprised of charge and

discharge voltages and inside resistances. They are studied by experiments in

the paper. Battery simulation model is established according to the

experimental data and the internal resistance of the model. The model can better

reflect the battery dynamic properties and can be used in pure electric vehicle

with dual-energy storage system simulation. It is also significant to study

energy management technology of dual-energy storage system

Keywords: battery, voltages, internal resistances, dual-energy storage system.

1 Introduction

Energy storage device is an important part which can influence the performance of

pure electric vehicle with dual-energy storage system. At present, the energy storage

device of the pure electric vehicle with dual-energy storage system is mainly

composed of the battery and the ultra-capacitor. The battery has the advantages of

high energy density, low self discharge rate, simple maintenance and clean

environmental protection [1]. Lead acid battery is used as the main energy source of

the energy storage system of pure electric vehicle. It has the advantage of mature

production technology, low price, enough material and good reliability [2-3].

2 Charging and Discharging Experiments and Results Analysis

of Battery

The lead acid battery is tested by the Ningbo Beit BTS5060C2 type power battery test

system. The range of test voltage is from 0 to 60V and the resolution ratio is 1mV.

The range of test current is from 200mA to 50A. The lead acid battery parameters in

the experiment are shown in Table 1.

Advanced Science and Technology Letters Vol.121 (AST 2016), pp.49-56

http://dx.doi.org/10.14257/astl.2016.121.10

ISSN: 2287-1233 ASTL Copyright © 2016 SERSC

Table 1. Lead acid battery parameters

type rated capacity

(Ah)

Rated

voltage (V)

size (mm) weight

(kg)

T-105 185 6 264×181×284 28

2.1 Test Scheme

In the experiment, charge the battery at first and then discharge the battery by the

BTS5060C2 type power battery test system. Charge and discharge the battery by the

test system is shown in Figure 1. At first, Charge the battery with 50A constant

current. When the battery capacities are 10Ah, end charge and stew in 30 minutes.

Then charge the battery with 45A constant current. When the battery capacities are

20Ah, end charge and stew in 30 minutes. The charge current is reduced to 5A at each

time, until the charge current is 5A. It takes 11 hours during the whole charging

experiment. And the total charge capacities are 100Ah. The discharging experiment is

similar to the charging experiment. Discharge the battery after the battery is full of

electricity for 3 hours. It takes 5 hours during the whole discharging experiment.

Fig. 1. Test experiment of the battery

2.2 Experiment results and data processing

Charging experiment voltage and current versus time curve is shown in Figure 2. As

can be seen from Figure 2, the voltages of the battery increase gradually with the

increase of the time in the process of the experiment. But the terminal voltage will fall

in the static time which is mainly due to the internal chemical reaction of the battery.

This phenomenon is called lag effect. Discharging experiment voltage and current

versus time curve is shown in Figure 3.

Advanced Science and Technology Letters Vol.121 (AST 2016)

50 Copyright © 2016 SERSC

Tota

l v

olt

ages

(V)

Total times(s)

Total times-total voltages Total times-total currents

Total cu

rrents(A

)

Fig. 2. Charging voltage and current versus time curve

Tota

l v

olt

ages

(V)

Total times(s)

Total times-total voltages Total times-total currents

Total cu

rrents(A

)

Fig. 3. Discharging voltage and current versus time curve

I

UR

Δ=

(1)

Where, I — the current value of constant current charge and discharge；

ΔU — the voltage change value of constant current charge and discharge.

Process the battery charging and discharging experiment data and get the battery

charge and discharge internal resistance and SOC data. They are shown in Table 2.

Table 2. Charge and discharge internal resistance and SOC measurement data

SOC 0.3

75

0.5 0.5

625

0.6

25

0.5

625

0.7

5

0.8

75

0.9

37

Charge internal resistance 0.0 0.0 - 0.0 - 0.0 0.0 0.0


Copyright © 2016 SERSC 51

/Ω 492 286 114 082 043 067

Discharge internal

resistance /Ω

- - 0.2

28

0.0

3

0.0

2

0.0

16

0.0

038

0.0

057

Establish the function expression of the internal resistance and SOC by least square

method of polynomial fitting according to data of Table 2.

R(x)=a0+a1x+a2x2+a3x

3+a4x

4+a5x

5 (2)

After fitting, the coefficients in the equation (2) are shown in Table 3.

Table 3. The relation coefficient of charge and discharge internal resistance

coefficient a0 a1 a2 a3 a4 a5

Charge internal

resistance

-

1.7

15 -50 79 -60 18

Discharge internal

resistance

1

97.6

-

1269.3

32

44.9

-

4125.4

26

08.5

-

656.3

The open circuit voltages of the battery during the discharge process are obtained

by the discharging experiment of the battery. They are shown in Table 4.

Table 4. Discharge voltage and SOC measurement data

Table 5. The relation coefficient of discharge voltage

Establish the function expression of the open circuit voltage and SOC by least

square method of polynomial fitting according to the data of Table 4.

E(y)=b0+b1y+b2y2+b3y

3+b4y

4+b5y

5+b6y

6 (3)

After fitting, the coefficients in the formula (3) are shown in Table 5.

3 Establish Battery Model

The lead acid battery model is established in Matlab/Simulink environment[5]. It

mainly includes the internal resistance and voltage model, power model, voltage and

current model and SOC model.

SOC 0.56 0.63 0.7 0.75 0.8 0.87 0.9

Discharge

voltage/V

1 5 5.3 5.4 5.4 5.5 5.5

coefficient b0 b1 b2 b3 b4 b5 b6

Discharge

voltage -18706 146290 -474790 818830 -791430 406480 -86670



3.1 Theoretical Model of Lead Acid Battery

The internal resistance model is used in electric vehicle simulation usually. It will be

equivalent to linear model of ideal voltage source and the resistance in series [6]. The

model is shown in Figure 4.

+

-

VE

+

-

R

I

Fig. 4. The internal resistance model

Fig. 5. Internal resistance and voltage model

Where, E — electrodynamic force；V — open circuit voltage；R — internal

resistance.

The parameters E and R in equivalent circuit can be obtained by the experimental

method.

3.2 Internal Resistance and Voltage Model

Establish the internal resistance and voltage model according to equation 2 and 3. It is

shown in Figure5.

3.3 Power Model

Power model is used to limit the power range of the battery current. It is limited

generally in battery SOC, the minimum operating voltage of the motor and the

equivalent circuit parameters. The maximum output power is expressed as:

R

VEVp max

max

-

(4)



Fig. 6. Power model

Fig. 7. Voltage and current model

3.4 Voltage and Current Model

The output power of the battery from Figure 4 is expressed as:

P=V·I (5)

Terminal voltage of the battery is expressed as:

V=E－I·R (6)

Substitute equation 6 into equation 5 and solute the equation then obtain

R2

RP4EEI

2 --=

(7)

3.5 SOC Model

The ampere hour calculation is used to calculate battery SOC in the paper. Suppose

the maximum capacity of the battery is Cmax, then the SOC of the K time can be

expressed as:



max

0max ∫

k

t-

=C

ηIdC

SOC

t

(8)

Where, I — current; η — discharge efficiency；

∫k

0t

t

Id — the capacity of the battery has been consumed.

Fig. 8. SOC model

Fig. 9. Battery simulation model

3.6 General Simulation Model of Battery

Incorporate Figure 5 to Figure 8 into a Simulink file. And establish the overall

simulation model of the storage battery. It is shown in Figure 9.

4 Conclusions

The battery charging and discharging experiments are carried out in the paper.

Experimental data show that the battery has the less charge and discharge resistance

and better storage characteristics. And open circuit voltage increases with the increase

of SOC. The battery simulation model is established according to the battery internal

resistance, which is important to dynamic coordination and energy distribution

technology of pure electric vehicle with dual-energy storage system.

References

1. Yang, J., Zhang, Z.: Electric vehicle battery management system based on microcontroller

and programmable devices. Mechatronics. 6, 29 (2004).

2. Liu, L.: Battery performance simulation and experiment of electric vehicle. A Dissertation

Submitted for the Degree of Master. (2005) Wuhan University of Technology, Hubei.



3. Massimo, C.: New dynamical Models of Lead-Acid Batteries. IEEE Transactions on Power

Systems. 4, 15 (2000).

4. Cao, J., Jiang, G.: A Study on Practical Use of DC-current Charging Method in the

Analysis of battery Internal Resistor. Electronic engineer. 12, 34 (2008).

5. Qiushi Science and Technology. MATLAB 7.0 from entry to the master, People Post Press,

Beijing (2006).

6. Zhao, X.: Modeling and Simulation of batteries for electric vehicles. A Dissertation

Submitted for the Degree of Master. (2004) Wuhan University of Technology, Hubei.



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