DM-i is no longer good? Why does BYD's new hybrid technology match Toyota's?

Recently, the news that BYD is about to launch the fifth-generation DM-i hybrid technology has attracted widespread attention. Today, we’ll take an in-depth look at this technology and its evolution.

The market for hybrid models of domestic independent brands has shown strong growth momentum in recent years, posing a strong challenge to the market share of hybrid models of joint venture brands. In this competition, BYD's DM-i super hybrid technology is particularly eye-catching.

BYD's research and development in the field of hybrid technology began in 2004. In 2008, the company successfully launched the world's first mass-produced plug-in hybrid vehicle, F3DM, which marked BYD's first breakthrough in the field of hybrid technology.

In the following more than ten years, BYD continued to conduct in-depth research and innovation on hybrid technology, accumulated rich experience and obtained numerous patents.

In 2020, BYD strategically segmented plug-in hybrid technology and launched DM-i super hybrid technology with "ultra-low fuel consumption" as its selling point. This technology, with its excellent fuel economy and power performance, It has been highly recognized by the market.

On January 11, 2021, BYD announced the official debut of DM-i super hybrid technology and confirmed that the technology will be applied to   Qin PLUS ( parameters | inquiry ) DM-i, Song PLUS DM-i, and Tang DM-i New models, pre-sales for these models started immediately. This is not only a milestone in BYD's technological innovation, but also another proof of its continued leadership in the field of new energy vehicles.

Of course, we are not committed to tracing the comprehensive development history of BYD's DM-i hybrid system, but focusing on an in-depth analysis of BYD's fifth-generation DM-i hybrid technology.

Not long ago, BYD revealed at a recent core management internal communication meeting that it would launch the fifth-generation DM system. According to relevant participants, the fifth-generation DM-i has a fuel consumption of 2.9L per 100 kilometers and can run on full fuel and full power. Close to 2000 kilometers.

The announcement of the news has undoubtedly triggered a wide-ranging and far-reaching impact. You must know that the fuel consumption per 100 kilometers of most hybrid models is basically controlled at a pace of 3-5L, and those below 3L are basically like the "Karman line" , very difficult to overcome.

Although it has not been confirmed, there is even news that BYD has categorically denied this statement. So, can this legendary fifth-generation DM-i be "effective"?

Let’s start with BYD’s patent picture of a suspected fifth-generation DM-i.

When I first looked at this patent drawing, I was deeply shocked because the technical effects it showed were strikingly similar to Toyota's THS.

That's right, it's Toyota's famous "sun gear" hybrid technology.

We can see that BYD's hybrid technology adopts a dual planetary gear design, which is different from the previous fourth-generation DM-i technology solution.

The system combines dual motors and a conventional differential to provide a front-drive/rear-drive hybrid mode, and has four working modes: pure electric four-wheel drive, hybrid four-wheel drive, extended-range rear drive, and high-speed engine direct drive.

So, does BYD’s design infringe the copyright?

We know that Toyota's THS hybrid technology has emerged in the early stages of hybrid technology. Its planetary row dual-motor hybrid system structure makes it unique in the field of hybrid power. With excellent fuel economy and stable and reliable quality, THS hybrid technology has won widespread praise in the global automotive market.

In fact, Toyota's THS hybrid system is not independently developed, but is based on the planetary hybrid technology of the American company TBW.

TBW Company applied for relevant patents in 1969, aiming to serve General Motors. The patent is valid until March 2, 1988. Toyota registered a patent for the THS planetary dual-motor hybrid system on May 20, 1996, and officially put it into mass production on the first-generation Prius model in 1997, ensuring the legitimacy of its technology. Since then, this technology has been widely used in Toyota's HEV gasoline-electric hybrid models such as Corolla/Ralink Twin Engine, Camry HEV, RAV4 HEV, Highlander HEV, Sienna SI∈NNA, etc., and has won wide recognition in the market.

Later, Toyota gradually released the THS patent in China, and in early 2019, it transferred the THS technology to its core parts supplier in China, Corun, at a symbolic price of "1 US dollar". It is worth noting that Geely Automobile holds a majority stake in Corun, so to a certain extent, Toyota actually indirectly transferred THS technology to Geely Automobile.

It should be pointed out that although Toyota has obtained the patented technology of THS, it has made a lot of improvements and upgrades based on the original technology. It is these efforts and innovations that enable Toyota to achieve today's brilliant achievements.

Let’s continue the topic and bring back BYD’s fifth-generation DM-i. So what is the difference between it and Toyota’s THS hybrid technology?

Judging from the patent drawings, the system is configured with one engine and dual motors, and achieves power transmission through two sets of carefully designed planetary gears, cleverly eliminating the need for traditional clutches, thus improving the overall connection strength and efficiency.

Looking into the underlying reasons for BYD's shift to planetary gear technology, people may wonder why it abandoned hybrid technology that had performed well.

BYD's old EHS hybrid system abandoned the traditional gearbox and was mainly driven by an electric motor in most cases, with the engine acting as a generator and only directly driving or driving the vehicle in parallel at high speed or rapid acceleration.

Although this design simplifies the structure and reduces costs, it cannot generate electricity at the same time during high-speed direct drive, which may cause the battery power to decrease during frequent acceleration, causing a rare stall phenomenon.

However, after the introduction of planetary gear technology, the power of the engine can be effectively distributed, cleverly solving this problem.

In addition, the use of a double planetary gear structure not only eliminates the clutch and reduces the volume, but also splits the power through the planetary row. The working pressure of the engine and motor is shared by the two planetary rows, improving the efficiency of the system. The engine's direct drive capability has been enhanced, making its efficient working range wider. At the same time, the motor can also achieve two-speed transmission through a planetary gearbox, thereby using a smaller power motor and reducing costs.

Although this design faces multiple challenges, such as the increased structural complexity, which leads to increased difficulty in adjustment, and the difficulty of planetary gear processing, domestic parts suppliers have also encountered bottlenecks in product durability. However, I firmly believe that BYD must have thought carefully in this regard, may have made a breakthrough at the technical level, and has successfully achieved mass production.

In addition to the new hybrid technology, the research and development of another BYD technology has also been hotly searched, and it is also the key to the fifth-generation DM-i hybrid system.

This is BYD’s second-generation blade battery.

Everyone may be familiar with blade batteries. Their advantages lie in their compact structure and efficient energy storage capabilities. Compared with traditional cylindrical or prismatic batteries, blade batteries have higher volume utilization and can provide more energy in a limited space. At the same time, its flat shape also makes it easier to integrate into various devices, providing designers with greater flexibility.

In addition to its structural advantages, blade batteries also excel in terms of safety. Due to the use of safety measures such as multi-layer structure and thermal isolation, the blade battery can quickly cut off the heat source when encountering abnormal conditions such as short circuit and overcharge to prevent the occurrence of thermal runaway of the battery. This self-protection mechanism greatly reduces the risk of battery fire or explosion, providing users with a safer power environment.

The second generation blade battery can be said to be the "PLUS" version of the first generation.

According to the collected information, the advantage of the second-generation blade battery lies in its significantly improved volume utilization. The increase of more than 40% allows more battery units to be accommodated in the same space, which directly leads to an increase in the energy density of the battery pack. This in turn significantly increases the vehicle's cruising range.

In terms of energy density, the energy density of the second-generation blade battery has reached 190Wh/kg. This improvement enables the cruising range of pure electric vehicles equipped with this battery technology to exceed 1,000 kilometers.

In addition, in order to meet the needs of different models and platforms, the second-generation blade battery has been carefully adjusted in cell size. In addition, the optimization of the thermal management system, including the addition of liquid cooling plates and thermal conductive layers, not only improves the charging and discharging efficiency of the battery, but also extends the service life of the battery and ensures stable performance under various working conditions.

Safety is another highlight of BYD's second-generation blade battery. Its puncture and collision resistance has been significantly enhanced. High-strength aluminum alloy plates added to the upper and lower sides of the battery core form a strong honeycomb structure, improving the battery's durability. Compressive strength and stiffness provide a solid guarantee for the safe operation of electric vehicles.