Week 7 State of charge estimation

1.Simulate the 3 test cases from harness dashboard and write a detailed report on the results

The above model has the battery management system ECU block which does the computations

This is the dashboard which indicates the battery states, balancing charging and driving

There are three test cases for each test sequence with different algorithm

Test case 1 driving, balancing, charging balancing.

Test case 2:-

Test case 3:-

Simulation done and result will be analysed

Result :-

Test case 1 :

Graph 1 is indicates the cell voltage, the voltages are changing when the current flow in and out of the cell there is sudden rise in the voltage till they reach 4.2V, this is because the after the time period of 3000sec next step is balancing mode and the vehicle is in standby condition after another 1000 sec the vehicle is in charging phase and the SOC increases almost 100%, this indicates the voltage is balanced

Graph 2 shows the charging state during constant current, graph 3 shows the temperature traces, we need to activate the thermal differences within a few degree celcius, graph 5 shows the SOC of each cell then other scope indicates the bms state at each of the balance command signals respectively

Test case 2 :

The voltage in initial state cells are deflecting in the same manner and dropping slightly, it has a four fluxuztion zone and they are stable for a while initialy at 80% of SOC and they are falling differnt time period and other scope indicates the BMS state at each of the conditions

Test case 3 :

From the above graphs all cells are intiated with different voltage and one having a higher voltage of 4.2V and the first one have 4.1V and remaining fall under the BMS range, the battery pack current i initiated in 20A then it fall to zero current in the end of simulation, there is constant current when the battery is in charging

graph 3 shows the temperature of the cells,the compared of cell no6 and cell no1, cell no 6 is higher temperature raises,the SOC of the cells is 80% and the system get charge the SOC get 100%

2.What is coulomb counting? Refer to the above model and explain how BMS implements coulomb counting for SOC estimation ?

Coulomb Counting Method. The Coulomb counting method measures the discharging current of a battery and integrates the discharging current over time in order to estimate SOC [20]. Coulomb counting method is done to estimate the , which is estimated from the discharging current, , and previously estimated SOC values

The SOC is one of the most important parameters for batteries, but its definition presents many different issues [5]. In general, the SOC of a battery is defined as the ratio of its current capacity () to the nominal capacity (). The nominal capacity is given by the manufacturer and represents the maximum amount of charge that can be stored in the battery. The SOC can be defined as follows:

The various mathematical methods of estimation are classified according to methodology. The classification of these SOC estimation methods is different in the various literatures. However, some literatures [5, 7] allow a division into the following four categories.

SOC(t) = SOC(t-1)+I(t)/Qn*`trianglet`

(i)Direct measurement: this method uses physical battery properties, such as the voltage and impedance of the battery.

(ii)Book-keeping estimation: this method uses discharging current as the input and integrates the discharging current over time to calculate the SOC.

(iii)Adaptive systems: the adaptive systems are self-designing and can automatically adjust the SOC for different discharging conditions. Various new adaptive systems for SOC estimation have been developed.

(iv)Hybrid methods: the hybrid models benefit from the advantages of each SOC estimation method and allow a globally optimal estimation performance. The literature shows that the hybrid methods generally produce good estimation of SOC, compared to individual methods.

Within the SOC estimation block, we have a coulumb counting, which is a subsystem

The sysytem does the estimation by coulomb counting equation, the advantages of the coulomb counting method is its low computational cost

Observations :-

the coulomb counting,the SOC elimination is done.

Temperature and current from the battery is given as input

current signal is given to the gain block

these inputs are given for integration where current will be integrated with respect to time

the ouput is given in another block where it is divided by capacity, this way the SOC is estimated