Everyone should have heard of the term '48V system'. Currently, 12V electric systems used in automobiles have been in use for more than 60 years. In 1988, SAE proposed to adjust the voltage to 42V. However, due to the technical level and R & D costs at that time, Automotive companies did not actively promote, still is 12V voltage 48V system is divided into 48V electrical system and 48V light mixing system.
At present, most cars will be equipped with start-stop system to reduce fuel consumption, but the power required to start and stop the system is relatively large, because P = U * I, in the 12V voltage invariably, want to start and stop the system power, It is necessary to increase the current, the mainstream engine starter power between 600W to 2000W, a simple mathematical operation, the current will be between 50A to 167A. Such a large current, the circuit system is a big burden.
In 2011, Audi, BMW, Daimler, Porsche and Volkswagen jointly launched the 48V system to meet the growing load requirements of automotive electrical appliances, and more importantly to meet emission regulations. As to why the 48V system is selected? 60V is the human safety voltage , 48V battery charging voltage up to 56V, close to 60V, 48V battery intraocular pressure is the highest voltage level under the safe voltage, and technology is always an exponential growth, the use of relatively high pressure for later technology paving a good platform.
From the table shows that want to achieve 4.0L per hundred kilometers of fuel consumption, simply increase the efficiency of internal combustion engine is obviously unrealistic, car hybrid, electric is the best way out.Although the electric car is the international trend, but due to cost High and supporting facilities, life issues, the short term can not be a lot of popularity, but the 48V hybrid system compared to high pressure mixing system, the low cost, to 70% energy saving effect.
48V light mixing system can be regarded as an upgraded version of 12V start-stop system, an increase of 48V voltage battery, 48V12V bidirectional DC / DC, 48VBSG (belt-driven startergenerator) / ISG (intergratedstartergenerator), electric supercharger, battery management system.
According to BSG's location there are P0 and P2 two designs.
The first BSG placed the front of the engine, this structure for the BSG layout is simple, small modifications to the vehicle, and can replace the original car generator.But the BSG and the engine can not be separated, so when taxiing, the engine drag Reduce the amount of energy that can be recovered and reduce CO2 emissions by 13% under NEDC conditions.
The second BSG / ISG is placed between the engine and the transmission. During the energy recovery phase, the engine can be disconnected and about 25% CO2 emission can be reduced. Pure electric drive can be realized through clutch. The BSG can be further upgraded to ISG, More integrated, more efficient.
For example, the Mercedes-Benz 48V system is supplied by BorgWarner and is comprised of a belt-less ISG integrated generator / motor, a 1kWh 48V Li-Ion battery, and AC / DC converters. ISG replaces the traditional starter, Can drive the vehicle, but also recover kinetic energy.A lot of people on the train, the first time put the start-stop system is closed, it is difficult to accept the noise and vibration caused by the start-stop system, and use ISG, start and stop the system more smooth, and the noise less.
The use of 48V system, the traditional use of belt-driven air-conditioning compressors, pumps, pumps and other electric drives can be used to reduce the belt drive losses, both increased power output, but also reduces the level of energy consumption, can be described as a stone two birds.Secondly, Increased voltage can increase the power of the vehicle electrical appliances, such as air conditioning compressor power increases, the cooling effect is strengthened, seat heating faster than before to reach the temperature, the comfort is also an upgrade.When the battery power is sufficient, ISG disconnects the engine and extinguishes the engine, greatly improving fuel economy.
In addition, 48V system can be equipped with high-power electronic turbine, the maximum speed of 72000rpm, and the constant power of 5kw, you can make up for the hysteresis of the exhaust gas turbines to improve the response of low-speed region. Another point is the lightweight, 48V system Reduce the parts of the drive belt, switch to electricity-driven, simplifying the design while reducing size and weight, improve fuel economy.
Regarding its own-brand outlook, Bosch offers them a complete solution, the BRS system, and plans to start mass production in 2017. Own brands can rely on Bosch to promote 48V system models.
Continental & Shaeffler
Developed jointly by the mainland and Schaeffler, the GTCII is based on a P2 architecture, with the BSG set up between the engine and the gearbox, driven independently by the motor, allowing the engine to be shut down on the coast and downhill sections, reducing engine drag, farther coasting and saving More fuel.
About batteries, 48V systems use lithium batteries as a means of storing energy. Johnson Controls, Hitachi, SAFT, and A123 each introduce 48-volt battery systems.
48V system for luxury cars and sports cars of different roles, the most important role for the luxury sedan 48V system is to maintain the smooth feel of the premise to save a little bit of fuel, while the sports car is the use of 48V system for performance, For example, in the acceleration with motor-assisted, so good results on the point. 48V system for use, different brands have different understandings and settings.
to sum up
In addition to the European car companies actively promote the popularity of 48V systems, Ford, GM, Hyundai and other depots have seen the future of 48V systems, said 48V models will be developed; the domestic Geely, FAW, BYD, Great Wall also confirmed the need to introduce 48V system, Europe The 48V system is highly expected by car makers, and should be followed by the Chinese market if Europe goes well. 48V light mixing is a cost, technology, and regulatory approach. Although fuel economy is inferior to high-pressure mixing systems, Many manufacturers can transition to the direction of new energy transfer
