# Electrification of a Class 8 Heavy-Duty Truck Considering Battery Pack Sizing and Cargo Capacity
## 2 Methodology  
### Battery Electric Powertrain Modelling  
The battery electric powertrain of a heavy-duty class 8 truck is modelled using AVL CRUISE M R2022.1 software [19]. The modelling process is indicated in Figure 1. The Mercedes Benz Actros 41-ton truck, featuring 8 wheels and 4-wheel drive (8 \(\times\) 4) is considered as the case study with its technical parameters presented in Table 1. The battery electric powertrain components in AVL CRUISE M R2022.1 software are presented in Figure 2 with the electric motor efficiency presented in Figure 3. The electrical network of the proposed powertrain includes two electric motors and six packs of batteries. The battery packs are sized and modelled based on specifications of Sony VTC6 lithium-ion battery. The battery pack specifications are provided in Table 2. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Component** & **Parameter** & **Value** \\ \hline \multirow{4}{*}{**Truck body dimensions**} & Distance from hitch to front axle [mm] & 3450 \\ \cline{2-3}  & support point height, bench test [mm] & 1050 \\ \cline{2-3}  & Wheel base [mm] & 3900 \\ \hline \multirow{2}{*}{**Trailer body dimensions**} & Distance from hitch to axle [m] & 7.7 \\ \cline{2-3}  & Pitching moment coefficient & 1 \\ \hline \multirow{2}{*}{**Truck nominal weight**} & Curb weight [kg] & 8000 \\ \cline{2-3}  & Gross weight [kg] & 8500 \\ \hline \multirow{2}{*}{**Trailer nominal weight**} & Curb weight [kg] & 19,000 \\ \cline{2-3}  & Gross weight [kg] & 32,500 \\ \hline \multirow{2}{*}{**Total carrying capacity**} & Truck [kg] & 500 \\ \cline{2-3}  & Trailer [kg] & 13,500 \\ \hline \multirow{2}{*}{**Aerodynamic Properties**} & Frontal Area [m\({}^{2}\)] & 8.48 \\ \cline{2-3}  & Drag coefficient & 0.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Truck and trailer bodies technical parameters. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Component** & **Parameter** & **Value** \\ \hline \multirow{4}{*}{**Cell**} & Nominal voltage [V] & 3.6 \\  & Current capacity [Ah] & 3 \\  & Energy capacity [Wh] & 10.8 \\  & Average weight [g] & 46.6 \\  & Estimated energy density [Wh/kg] & 232 \\ \hline \multirow{4}{*}{**Pack**} & Cells in series & 176 \\  & Cells in parallel & 35 \\ \cline{1-1}  & Module energy capacity [kWh] & 66.5 \\ \cline{1-1}  & Number of Packs & 6 \\ \cline{1-1}  & Packs total energy capacity [kWh] & 399 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Battery pack parameters. Figure 1: Flow diagram of modelling process. Figure 2: Block diagram for AVL vehicle model. The originally diesel Mercedes Actros truck is considered the case study in this paper. Therefore, the weight change associated with the electrification of this truck is obtained based on the weight of components exchanged. These values are presented in Table 3. The transmission and drivetrain weight were assumed to be equal for the diesel and electric powertrains. The mass loss from removing the fuel and fuel tank was estimated by using 50% of the full capacity tank weight for the Actros as a conservative estimate for the average amount of fuel in the truck during long-haul driving. The electric vehicle weight addition includes weight from the two motors, battery pack, inverter, and DC/DC converter. Dual motors were used to obtain high efficiency compared to a single larger motor [20], and permanent magnet motors were selected for their high specific torque [21]. In order to determine the effect of pack size on weight, the required structural mass for a given energy capacity was determined based on previous studies. The cell energy density was used to calculate pack energy density, based on a 60% percentage weight of cells to total pack weight. This value was chosen based on typical gravimetric energy densities achieved with current battery packing methods [22; 23; 24; 25]. The resulting pack gravimetric energy density is 140 kg/kWh. The pack weight was then calculated for each pack size by dividing the power capacity by 140 Wh/kg.