Another technical solution for power-type plug-in hybrid: A brief discussion on Volvo T8 plug-in hybrid technology

Plug-in hybrid power system, referred to as PHEV, is the mainstream in the current new energy vehicle market. Compared with pure electric vehicles, it has no range anxiety. Compared with extended-range vehicles (which are essentially also PHEVs), the traditional series-parallel PHEV system has the advantage of lower fuel consumption when the battery is depleted.

However, what many people may not know is that plug-in hybrid systems are actually divided into many technical forms, and each technical form actually corresponds to the company's understanding of the plug-in hybrid system. On the eve of the Guangzhou Auto Show, Volvo held a small plug-in hybrid technology sharing meeting in Guangzhou, where not only some interpretations were made on the mainstream plug-in hybrid forms, but more importantly, the technical route and technical solutions of the Volvo T8 plug-in hybrid system, which are not very familiar to the outside world, were also interpreted at this sharing meeting.

At present, the common plug-in hybrids are divided into two major directions: series-parallel plug-in hybrids and series plug-in hybrids. Another name for series plug-in hybrids is familiar to everyone: extended-range type. But as for series-parallel plug-in hybrids, they are actually divided into two categories: energy-saving plug-in hybrids and power-type plug-in hybrids.

The names actually give you an idea of ​​the general properties of these two plug-in hybrid systems. As the name implies, the entire system construction and system implementation of energy-saving plug-in hybrids revolve around the two words "energy saving". Typical representatives of energy-saving plug-in hybrids include BYD DM-i, SAIC DMH and other systems. These systems have several common characteristics: First, there is basically no P4 motor. Regardless of whether it is a P1+P3 or P2 solution, these systems basically use a coaxial motor system around the engine.

Secondly, this type of system usually weakens the power output of the fuel engine and emphasizes the output of the motor. Therefore, most of them are equipped with a plug-in hybrid engine with low output power. This type of engine can usually achieve high thermal efficiency at a fixed speed. By tilting the output of the entire system towards the motor + fixed speed high thermal efficiency engine + large battery, this type of system can usually achieve a fairly high comprehensive cruising range and fuel consumption and power consumption data.

The opposite of energy-saving plug-in hybrids is power-type plug-in hybrids. As the name suggests, this type of plug-in hybrid system focuses on performance output. Energy saving is not completely ignored, but it is not a high priority. Therefore, for power-type plug-in hybrid systems, the primary consideration is power output, not just energy saving performance.

There are actually two technical routes for power-type plug-in hybrids. One is the Chinese route, represented by various domestically produced performance plug-in hybrids. The other is the European route, represented by Volvo's T8 plug-in hybrid. The guiding ideology of the Chinese route is "weakening the internal combustion engine and strengthening the output of the motor." Chinese power-type plug-in hybrids are usually equipped with a 200-250 horsepower 2.0T engine, and some models are even only equipped with a 1.5T high-power model. However, this type of solution will extremely emphasize the output power of the motor, including power-type plug-in hybrids of many brands such as Zhiji and BYD are basically of this model. For example, the Denza Z9GT plug-in hybrid version has a comprehensive maximum horsepower of nearly 1,100, but more than 860 horsepower is provided by the motor, and the 2.0T engine only provides 200+ horsepower.

The Volvo T8 plug-in hybrid is a representative of the European power plug-in hybrid, also known as a split power plug-in hybrid. The guiding ideology of this type of system is completely opposite to that of the Chinese plug-in hybrid, which is a strong engine and weak motor type. Taking the Volvo T8 plug-in hybrid as an example, the structure of this system is a high-power internal combustion engine + a P1 coaxial drive motor, and a P4 independent drive motor is added to the rear axle. This is a split plug-in hybrid system.

In addition to the completely different system construction method from the Chinese plug-in hybrid, Volvo's T8 plug-in hybrid system is also very different from the Chinese performance plug-in hybrid system in the three-electric system, especially the battery pack that has the greatest impact on various performances. The Volvo T8 adopts a central battery pack design. This battery pack is not like the Chinese plug-in hybrid, where a large flat battery is placed directly at the bottom of the chassis. It is a rectangular-like structure installed on the longitudinal centerline of the vehicle, and the specific location is roughly in the front and rear rows of the passenger compartment.

This quasi-rectangular structure has both advantages and disadvantages in terms of structure. The advantage is that the collision safety is much better than that of a flat battery. Since almost the entire body of the car serves as a collision buffer, the battery pack can be guaranteed not to have thermal runaway even in a severe collision. And since this battery is installed directly on the center axis of the car body, it is also good for the dynamic handling of the entire vehicle.

But this method naturally has its disadvantages, mainly because the battery pack will occupy the passenger compartment space. But we can also see on Volvo's mass-produced cars that the battery pack occupies most of the space in the car's center console, glove box and other places. The overall space impact is actually not very large.

To be fair, Volvo's T8 plug-in hybrid is one of the representative technologies of European power plug-in hybrids among current joint venture luxury brands. In fact, it is stronger than many luxury brand competitors in the field of joint venture luxury cars. It can be said that the T8 plug-in hybrid is the representative technology of European power plug-in hybrids today.