Project 2 Thermal modeling of battery pack

Aim:

Thermal modeling of the battery pack.

Objective

For a 10-cell series lithium-ion battery model, simulate the thermal effects and compare life cycle performance at various temperatures, and charge & discharge rates using MATLAB.

10 Cell series lithium-ion:

10 Cell are connected in series,

Here lithium-ion batteries (table-based) are connected in series, the thermal port is connected to the temperature source through a convective heat transfer and sensed by a thermal sensor.

The controlled current source is given to the battery through the signal builder. The current from the controlled current source is sensed by the current sensor then the SOC is called by the coulomb counting method.

Coulomb counting expression is followed by

`Soc(t)=Soc(t-1)-int((I(t))/Q).dt`

where

• SOC(t) = Battery state of charge at time t
• SOC(t-1) = Battery initial state of charge (previous state)
• I(t) = Charge/ discharge current at time t. I(t) is positive for charging and negative for discharging.
• t = Time in an hour
• Q = Battery pack capacity in ampere-hour.

Current is integrated (Discharge or charge capacity at the time) and this integrated current is divided by battery capacity.

After diving into the battery capacity, then this value is subtracted with 100(for percentage) or 1(For values between 1 to 0)

SOC and temperature are shown in the scope.

Input signal:

The signal builder gives the signal as per the user's wish and the input signal shown above.

For the temperature of 298.15 kelvin

Battery discharge from 100 to 99.993% Soc and temperature varied from 298.15 to 298.65 Kelvin

For the temperature of 300.15 kelvin

Battery discharge from 100 to 99.993% Soc and temperature varied from 300.15 to 300.65 Kelvin.

For the temperature of 318.15 kelvin

Battery discharge from 100 to 99.993% Soc and temperature varied from 318.15 to 318.95 Kelvin.

Calculating the life cycle of the table-based battery is complicated. So a generic battery model is used and 1 battery is taken.

Model:

Signal builder is connected to the through the controlled current source. Output is shown in the scope.

Battery parameter: Enable Temperature effect and aging effects to know the temperature and life cycle of the battery.

3.3V, 2.3Ah preset battery is selected.

Various temperature:

The temperature is -10 Degree Celsius(external temperature which is set by the user):

The sawtooth signal is given as an input to the battery and the Output are SoC, life cycle, Temperature, and Voltage of the batteries

The above figure shows the characteristics of batteries under -10 Celsius,

The battery initially fully discharged around 200 sec, after that the soc ranged between 0 to 50% repeating till 3600 sec.

In this temperature, the aging takes place slowly between 0 to 0.03 cycles only, which is a very smaller value and the battery temperature is raised enormously (134 degrees Celsius). the battery temperature is ranged from 20 to 135-degree celsius. Even though the external temperature is -10 degrees celsius the battery's internal temperature is raising due to the charging and discharging of the battery and its chemical properties of the batteries.

The temperature is 0 Degree Celsius:

The battery is initially fully discharged around 200 sec, Battery is charged to 48.5% and discharged to 0%, and this cycle is repeated for 3600sec. Voltage ranges between 3.4 to 0.

In this temperature, the aging takes place slowly between 0 to 0.275 cycles only, which is a very smaller value and the battery temperature is raised enormously (116 degrees Celsius). the battery temperature is ranged from 20 to 116-degree celsius.

The temperature is 10 Degree Celsius:

The battery is initially fully discharged around 200 sec, Battery is charged to 49.25% and discharged to 0%, and this cycle is repeated for 3600sec. Voltage ranges between 3.4 to 0.

In this temperature, the aging takes place slowly between 0 to 2.34 cycles only, which is a very smaller value and The battery temperature is ranged from 20 to 88.5-degree Celsius.

The temperature is 20 degree Celsius:

The battery is initially fully discharged around 200 sec, Battery is charged to 50.2% and discharged to 0%, and this cycle is repeated for 3600sec. Voltage ranges between 3.9 to 0.

At this temperature, the aging takes place slowly between 0 to 16.71 cycles. The battery temperature is ranged from 20 to 32.7-degree Celsius.

The temperature is 24 degree Celsius:

The battery is initially fully discharged around 200 sec, Battery is charged to 50.5% and discharged to 0%, and this cycle is repeated for 3600sec, but here repeating cycle is not discharged fully(due to the aging effect range of SOC being decreased). Voltage ranges from 4 to 0 and its range is decreased due to aging.

At this temperature, the aging takes place slowly between 0 to 34.75 cycles. The battery temperature is ranged from 20 to 34.7-degree Celsius.

The temperature is 28 degree Celsius:

The battery is initially fully discharged around 200 sec, Battery is charged to 51.2% and discharged to 0%, and this cycle is repeated for 3600sec, but here repeating cycle is not discharged fully(due to the aging effect range of SOC being decreased,51.2 to 6% at 3600 sec). Voltage ranges from 4 to 0 and its range is decreased due to aging.

At this temperature, the aging takes place slowly between 0 to 70 cycles. The battery temperature is ranged from 20 to 36.7-degree Celsius.

The temperature is 32 degree Celsius:

The battery is initially fully discharged around 200 sec, Battery is charged to 51.2% and discharged to 0%, and this cycle is repeated for 3600sec, but here repeating cycle is not discharged fully(due to the aging effect range of SOC being decreased,51.2 to 10% at 3600 sec). Voltage ranges from 4 to 0 and its range is decreased due to aging.

At this temperature, the aging takes place slowly between 0 to 139 cycles. The battery temperature is ranged from 20 to 39.1-degree Celsius.

The temperature is 36 degree Celsius:

The battery is initially fully discharged around 200 sec, Battery is charged to 51.2% and discharged to 0%, and this cycle is repeated for 3600sec, but here repeating cycle is not discharged fully(due to the aging effect range of SOC being decreased,58.2 to 17% at 3600 sec). Voltage ranges from 4 to 0 and its range is decreased due to aging.

At this temperature, the cycle is between 0 to 263 cycles. The battery temperature is ranged from 20 to 41.55-degree Celsius.

The temperature is 40 degree Celsius:

The battery is initially fully discharged around 200 sec, Battery is charged to 51.2% and discharged to 0%, and this cycle is repeated for 3600sec, but here repeating cycle is not discharged fully(due to the aging effect range of SOC being decreased, 62.7 to 26% at 3600 sec). Voltage ranges from 4 to 0 and its range is decreased due to aging.

At this temperature, the aging takes place slowly between 0 to 472 cycles. The battery temperature is ranged from 20 to 44.34-degree Celsius.

The temperature is 45 degree Celsius:

The battery is initially fully discharged around 200 sec, Battery is charged to 51.2% and discharged to 0%, and this cycle is repeated for 3600sec, but here repeating cycle is not discharged fully(due to the aging effect range of SOC being decreased,70 to 40% at 3600 sec). Voltage ranges from 4 to 0 and its range is decreased due to aging.

At this temperature, the aging cycle is between 0 to 903 cycles. The battery temperature is ranged from 20 to 48.1-degree Celsius.

External Temperature(`circ celsius`)	Cell Temperature(Celsius)	Life Cycle	SOC(Range Reduced)
-10	Varies between 20 to 135	0.03 Cycles	51.2%(200s) to 51.2%(3600s)
0	20 to 116	0.275 Cycles	51.2%(200s) to 51.2%(3600s)
10	20 to 88.5	2.34 Cycles	51.2%(200s) to 51.2%(3600s)
20	20 to 32.7	16.71 Cycles	51.2%(200s) to 49.85(3600s)
24	20 to 34.7	34.75 Cycles	51.2%(200s) to 47.9%(3600s)
28	20 to 36.7	70 Cycles	51.2%(200s) to 45.2%(3600s)
32	20 to 39.1	139 Cycles	51.2%(200s) to 41.2%(3600s)
36	20 to 41.55	263 Cycles	51.2%(200s) to 41.2%(3600s)
40	20 to 44.34	472 Cycles	51.2%(200s) to 36.7%(3600s)
45	20 to 48.1	903 Cycles	51.2%(200s) to 30%(3600s)

As the external temperature decreases Cycles also decrease and the aging takes place slowly. But battery temperature increases enormously which may damage the battery pack

At -10 degree celsius, the battery temperature raises to 135-degree celsius from 20-degree celsius(initial temperature). The life cycle is very low and the Soc range is full(As we know that the soc range will decrease as no of the cycles increases i.e charging and discharging )

At 28 degree celsius, the battery temperature rise to 36.7-degree celsius, the cycle is 70, and the Soc range is reduced from 51.2 to 45.2%.

At 45 degree celsius, the battery temperature rises to 48.1, cycle 903 which highest, and the Soc range is reduced to 30% from 51.2%.

From this, we get to know that at high temperatures, the battery life cycle reaches its maximum (aging is quickly), Soc range gets reduced as faster than at low temperatures.

Using a battery between 20 to 28 is optimal. Extending the battery life, Soc range decrease takes more time than 45-degree environment battery and cell temperature is maintained.