Project 2 Thermal modeling of battery pack

Model

Here we have designed a 10 cells series battery conection and charging and discharging is carried out and the effect of the temp on SOC is checked. The design has a blocks namely battery, temp source , convective heat transfer, conductive heat transfer, current sensor, voltage sensor and a courent source.

The 10 cells are connected in series and conductive heat transfer is placed between cells and the temp source is connected to battery through convective heat transfer block .

a temp sensor is connected to check the battery temp. A voltage sensor is connected parallel to the battery and a current sensor is connected in series to get the current. The coulomb counting method is used to estimate the SOC of the battery pack .

A signal builders is connected to the controlled current source and signal that discharges batteyr at 4.2A for 250sec and then chrages the battery at 2.1A for rest of the time is provided as input signal.

Battery

Here we use a cell with capacity 4.2Ah

Conductive heat transfer

Convective heat transfer

SOC estimation

From current SOC is obtained By coulomb counting method.

The current is fed to the integrator and the obtained current is in Asec it is then converted to Ahr and the divided by the max capacity and the output is fed to a gain now we obtain DOD which is then subrtacted from 100 to obtain SOC.

Result

We initially set the temp as 300k and the model was run for 500 sec.

the temp of the battery reaches 300.2 and the final Soc of the battery is 91.44

In the plot we can see that the temp rises during discharging and during chrging it gets reduced in a small amount. The voltage also drops and rise during discharging and charging respectively

making temp 310

SOC reached 78.78 and the temp is 309.6

later the temp is raised to 325k

The temp of the battery raised to 323.1 and the SOC of the cells reached 73.11. a signficant decrease in SOC can be observed when the temp is increased.

making the temp 350k

the SOC has no much change after certian raise in temp has reached

Conclusion

We can observe a significant drop in SOC when the temp is increased .

The temp rise charge and discharge at 1C rate is differect from charging and discharging at .5C.