Current status and prospects of 48V mild hybrid system

With environmental regulations becoming increasingly stringent and electric vehicles on the rise, many people wonder why automakers continue to develop mild hybrid technology based on internal combustion engines. It's understandable that many drivers, like me, are not ready to completely give up gasoline and diesel and turn to electric vehicles. Therefore, the automotive industry has to come up with alternatives that not only attract buyers but also ensure that automakers can meet the CO2 emissions and fuel economy targets required by various countries.

One of these technologies is the mild hybrid system for the 48-volt battery. It has quietly captured a lot of market share without anyone noticing, and now even the entry-level A-Class sedan can find a 48V mild hybrid system, which is a welcome entry point for consumers who want to go green. The technology offers a range of advantages and can be tailored to the wishes of the automaker without worrying about compromising the driving experience.

What is a 48V mild hybrid system ?

It refers to a mild hybrid system with a voltage of 48 volts, which replaces the traditional lead-acid battery with a lithium-ion battery, and replaces the traditional starter motor and generator with a BSG motor to provide auxiliary power when necessary and can realize energy recovery.

According to the architecture of electrified components and the location of the motor, the automotive industry divides hybrid technology routes into P0, P1, P2, P3, P4 and combinations therebetween.

P0 – The motor is placed before the gearbox, and the belt drives the BSG motor (starter and generator motor).

P1 - The motor is placed before the gearbox and mounted on the engine crankshaft, before the clutch (where the flywheel used to be).

· P2-The motor is placed at the input of the gearbox, after the clutch (between the engine and the gearbox).

·P3-The motor is placed at the output end of the gearbox, sharing the same shaft and output with the engine.

P4-The motor is placed after the gearbox, separate from the engine output shaft, and generally drives the unpowered wheels.

The 48V mild hybrid system can actually choose any of the above structures, but the most mainstream method now is to use the P0 architecture. The motor of this structure integrates the function of the starter, and the entire engine is more compact. Combined with the 48V battery, it can drive the mechanical compressor of the air conditioner when the engine stops at the traffic light, thereby achieving a certain fuel saving effect.

As far as the engine architecture is concerned, the P0 structure does not require any changes to it, so from the perspective of investment, development time and complexity, the P0 structure is very popular and has and will occupy the majority of the 48V market for a long time in the next few years.

Of course, the P0 structure also has its irreconcilable disadvantages. The efficiency of the soft connection of the belt is still limited, so the power of adding power to the engine and recovering kinetic energy is limited. Moreover, due to the limitation of the belt drive, it must keep pace with the engine, so it cannot run independently to provide pure electric driving.

Some powertrain experts believe that the P4 layout is technically the ideal solution if cost is not a consideration. The motor is directly connected to the wheels, which is not only the most energy-efficient setup, but also supports four-wheel drive. With the P0 layout, Valeo was able to improve fuel efficiency by 5-15%. In contrast, the P4 structure can improve fuel efficiency by 20% to 25%. Unfortunately, the P4 structure cannot switch between pure electric drive and pure engine drive at will, is not conducive to vehicle handling and comfort, and has relatively high costs and large changes in vehicle structure.

Advantages of 48V mild hybrid system , why promote 48V mild hybrid technology

A huge advantage of the 48V mild hybrid system for vehicle manufacturers is that the vehicle structure does not need to be adjusted significantly. Compared with traditional fuel vehicles, the following are some of the differences:

48V lithium-ion battery replaces traditional 12V lead-acid battery

Use BSG electric motor to replace the starter motor and generator on the traditional engine

Electrical system transformation

Relatively speaking, these changes are simple and inexpensive, but will improve fuel economy and emissions to a certain extent.

At this point, many people will ask, can 48V technology really help cars improve performance? Are the 48V mild hybrid models currently on the market better than before?

Simply put, the 48V hybrid system mainly saves fuel and reduces emissions by shutting down the engine during temporary parking and providing certain assistance from the motor during starting and sudden acceleration, thereby balancing the power output and making the engine operate in a high-efficiency range. It can also recover energy during the journey.

Another very important factor is that there are more and more electronic/electric systems in cars now, and the 12V battery system has become incapable of doing so. 48V can power more automotive devices, such as e-turbo, which can accelerate faster than traditional turbo, but cannot be configured on traditional 12 V cars. There are also many in-vehicle comfort configurations that are also large electricity consumers, such as seat heating, ventilation, electric adjustment, in-vehicle multimedia entertainment systems, etc., which have an increasing demand for electricity. There are also more and more applications for assisted driving, and its systems, including adaptive cruise control and active braking, all require electricity.

The impact of my country's "double points" policy on 48V technology

The dual-credit policy was released in September 2017 and implemented in April 2018, more than two years have passed. One of the original intentions of the country to introduce the dual-credit policy is to improve automobile energy efficiency, reduce fuel consumption, and promote the rapid development of new energy vehicles. The so-called dual credits are: CAFC (Corporate Average Fuel Consumption) credits and NEV (New Energy Vehicle) credits, or simply fuel consumption credits and new energy credits.

Simply put, the double points of each enterprise cannot be negative. If the negative double points are not compensated on time, the enterprise will be punished by suspending the declaration of high-fuel consumption products and suspending the production of high-fuel consumption products.

It should be noted that in the calculation of points, only the vehicles sold are counted. So if the sales of new energy vehicles are poor, no matter how many are produced, it is meaningless. At this time, various vehicle manufacturers will send 48V technology to the stage, because at present, most drivers still prefer cars with traditional engines, so this intermediate technology is needed to meet the market demand in the next decade or so. Although 48V mild hybrids are not counted as NEV vehicles, they can reduce the CAFC value and balance the total points, thereby reducing or even avoiding fines.

Cost Factors

48V technology has been widely used for some time, and the additional cost per vehicle has dropped to about 4,000-6,000 RMB, while traditional hybrid systems are 3,000-4,000 euros, so compared to hybrid systems, 48V mild hybrids are becoming more and more popular in the mass market.

On the other hand, the annual fuel savings of a 48V mild hybrid car is only about 1,000 yuan, which means it will take about five years to recover the increased cost. For many ordinary consumers, this is not cost-effective.

Therefore, among the customer base willing to accept new energy vehicles, 48V mild hybrid vehicles are popular; but in the eyes of most ordinary customers, 48V mild hybrid is still not in their car purchase options. The future of 48V is still unknown.