# Electrification of a Class 8 Heavy-Duty Truck Considering Battery Pack Sizing and Cargo Capacity
## 3 Result and Discussion
### Parametric Analysis  
The effects of battery pack size variations on the cargo capacity of the proposed battery electric truck are shown in Figure 9. Electrification of the truck resulted in a decrease in its cargo capacity from 13.5 tons to 11.77 tons, 11.36 tons, and 10.96 tons by increasing the battery pack size to 399 kWh (35 rows), 456 kWh (40 rows), and 513 kWh (45 rows), respectively. The difference between the desired and actual velocity of the proposed battery electric truck for different battery pack sizes at 100% cargo load is shown in Figure 10. The fluctuations in actual velocity in cruising velocities (desired profile) are due to the existence of road inclination, resulting in activation and deactivation of the brake pedal. The desired velocity is caught in most of the points, and minor deviation is observed in sudden acceleration point following from electric motor moment of inertia. Furthermore, Figure 10 also  
Figure 8: The estimated parameters for second order ECM using HPPC data: (**a**) open circuit voltage, (**b**) static ohmic resistance, (**c**) dynamic constants resistances, (**d**) first time constant and (**e**) second time constant in various state of charges. indicates that desired torque at various speeds is delivered by dual motors installed in the battery electric powertrain. The battery pack voltage change during travel for different case scenarios is shown in Figure 11. By increasing the battery size, the overall voltage of the pack increased, while increment of occupied cargo capacity resulted in decrease of battery pack voltage due to faster discharging of the pack leading to sharp fade of voltage. There are four sharp increases in voltage during travel due to sharp changes in velocity as can be seen in Figure 11. When the velocity decreases sharply, a drastic increase in voltage is also observed. These sudden voltage jumps can be controlled by employing a programmed battery management system. In the last period of travel, steep increase of voltage is seen for R35L50, R35L100 and R40L100 due to reaching below 30% in SOC (Figure 12). As indicated in Figure 8a, there is a fluctuation in open circuit voltage for SOCs between 20% and 30%. The same trend is reflected in battery pack voltage, as is demonstrated in Figure 11. The  
Figure 10: Truck desired and actual velocity for different case studies in various times in proposed driving cycle. Figure 9: Effect of battery pack size on cargo capacity. most voltage fade belongs to R35L100 case scenario with lowest size of the battery and highest cargo capacity. This led to a sharper decrease in the battery pack voltage due to high power demand, resulting in a lower SOC being reached at the end of travel compared to other scenarios. The battery power change is shown in Figure 13 in various time steps of the driving cycle for different scenarios. The discharging power increased during truck cruising speeds due to the increase in the cargo load. The highest charging peaks are achieved in the R45L100 scenario due to the existence of a larger battery and a large load (cargo) resulting in higher values of regenerative brake energy. However, the charging sudden peaks should be capped as well as discharging sharp peaks to prevent the battery from being damaged due to high temperature. Figure 11: The battery pack voltage variations during travel for different scenarios. Figure 12: The battery pack SOC variations during travel for different scenarios. The cumulated energy recovered by regenerative brakes and consumed energy during travel for different scenarios is shown in Figure 13(a),b. Regenerative brake energy increased from 6.94 kWh to approximately 9.87 kWh due to the increment in the truck cargo capacity between 10% and 100%. In addition, an increase in the battery cell rows in the packs from 35 to 40 and 45 resulted in energy recovery increases of 1.73% and 3.46% for 10% load, 0.98% and 2.2% for 50% load and 0.41% and 0.74% for 100% load, respectively.