61 Vehicle Architectures and Design FIGURE 3.9 Block diagram of a series PHEV. back to the grid during peak periods. The concept is known as ‘Vehicle-to-Grid’ power or V2G. The vehicle can be recharged again during off-peak periods. The major drawback of the PHEV is the poor well-to-wheel (WTW) efficiency compared to conventional gasoline and regular hybrid vehicles. This is because the PHEV has the poor effi- ciency segments of both the IC engine vehicle and the EVs in the WTW energy conversion pathway. However, the PHEV has the potential to be both more efficient and environmentally friendlier if the electricity to recharge the batteries can be obtained from renewable sources.
The higher capacity battery in the PHEV increases the mass of the vehicle. The added mass affects the performance; components have to be sized for higher power rating to achieve good per- formance. The batteries are also quite expensive, and as a result, the cost of the vehicle is also high. The zero-emission range of the PHEV depends on the way the vehicle is used. The batteries used in the vehicle must be charged using grid electrical power to achieve maximum efficiency and cost reductions. The benefits of the PHEV decrease if the recharging capability through plug- in is unavailable. The use of the engine to charge the batteries should be minimized to maximize efficiency.
Energy is always lost during charging and discharging of the battery-pack. The desired mode of operation when the IC engine has to be used is the series mode. 3.4 ELECTRIC VEHICLES: SKATEBOARD CHASSIS The BEVs with its high acceleration performance, quiet and smooth power, wide torque range, lower operating costs and minimal maintenance are not only getting widespread customer acceptance but also enabling numerous new manufacturers challenge the traditional vehicle manufacturers. The emergence of many new manufacturers can be attributed to the simplicity and flexibility in packag- ing the electric powertrain within the chassis of the vehicle.
In an EV, the only propulsion compo- nents is the electric motor although there can be multiples of those powering one or more axles or mounted on the wheel hub. The equivalent architecture of the different motor, inverter and gearbox arrangements in a vehicle can be simplified to the block diagram shown in Figure 3.10. The elec- tric motor and inverter ratings of the electric powertrain determine the propulsion capability of the vehicle. The energy storage or battery capacity determines the range of the vehicle on a full charge.
The most popular electric powertrain component is emerging to be the combined unit of an elec- tric motor, inverter and gearbox, referred to as the e-powertrain, which is to be placed in an axle of a vehicle known as the e-axle. The e-powertrain simplicity has also led the industry move towards a skateboard chassis where the energy source and e-powertrain for the vehicle are enclosed within the chassis. This type of design thinking allows for greater flexibility and customization for different types of vehicles within the same chassis.
The design was originally envisioned and implemented by General Motors in 2002 in AUTOnomy chassis on top of which the Hy-Wire concept vehicle was built later that year. The skateboard concept has been adopted more recently by Tesla, Rivian and Interface Circuit Converter Engine Generator Battery Bi-directional power flow Unidirectional power flow Motor Wheels Interface Circuit Converter Motor Wheels