How much you know about 48V car system?

How much you know about 48V car system?

Under increasing environmental pressure, new energy vehicles quickly get consumer's attention with support of national policies. However with subsidies declining year by year, accelerated promotion of "double points" policy and average fuel consumption limit to 5 liters/100 kilometers 2020, energy saving and emission reduction has become a double-edged for Car Company. At this time a very popular vocabulary 48V got our attention, what is 48V?

48V system concept

The 48V system refers to a system voltage of 48V. It replaces the traditional lead-acid battery with a power-type lithium-ion battery with less than one kilowatt of electricity. It replaces the traditional starter motor and generator with a BSG motor. In addition to the automatic start-stop function, it can also provide auxiliary power to the vehicle when necessary.

In general, the 48V system consists of three major components: a motor, a lithium-ion battery pack, and a DC-DC converter. The 48V system is generally connected in parallel with the internal combustion engine. Compared to high-pressure hybrid systems, the 48V micro-hybrid system offers two-thirds of the full hybrid power at one-third the cost, improving fuel economy by 15% to 20%.

The 48V can also be used to drive an electric supercharger (e-ger). The electric supercharger replaces the traditional waiting exhaust gas to maximize the speed of the turbine, which makes the acceleration process more rapid and the hysteresis is not so significant.

48V system origin

In 1918, the car was first introduced into the battery. With the birth of the starter, the battery was widely used in 1920. At that time, the voltage level of the battery was 6V, and the positive pole was grounded. Due to the increase in displacement of internal combustion engines and the emergence of high compression ratio internal combustion engines, 6V batteries have been unable to meet power requirements. In 1950, voltage levels began to evolve to 12V, and until now, 12V voltage systems have been ruled for more than 60 years.

In 1988, SAE (Society of Automotive Engineers) proposed to increase the standard voltage to 42V. Due to the technical level at the time and the high cost of replacing electrical components, the automobile companies did not actively promote the implementation, and eventually died. The car is still a 12V system.

At present, the fuel saving potential of the technology of 5 liters/100 kilometers of fuel consumption limit 12V idling start and stop has reached the bottleneck. Idle start and stop and brake recovery are effective energy-saving technical means, but in the 12V system, due to the voltage is low, it is not well played, and the technical cost is increased while the energy saving effect is limited.

In 2011, Audi, BMW, Daimler, Porsche, and Volkswagen jointly launched a 48V system to meet the growing demand for on-board loads and, more importantly, to meet stringent emissions regulations in 2020. And subsequently released the 48V system specification LV148.

48V light mixing system advantages and disadvantages

Pure electrification is the goal of the car, but due to battery life problems, charging problems, and cost issues, it cannot be widely used in the short term. The 60V is a safe voltage, which means that if the voltage below 60V does not require additional safety measures, the charging voltage of the 48V battery is up to 56V, which is very close to 60V, that is, the 48V battery voltage is the highest voltage level under the safe voltage.

Compared with the high-pressure hybrid system, the 48V light-mixing system has lower cost, but can achieve most of the energy-saving effect of the high-pressure hybrid system (battery voltage >100V). According to Delphi's calculation, the 48V light-mixing system is the cost of the high-pressure light-mixing system. 30% can achieve 70% energy saving effect of high-pressure light mixing system.

Advantages:

1. Reduce CO emissions, increase fuel rates, and adapt to national policies.

2. Below 60V safe voltage, no additional voltage protection is required, and the cost is lower than the high-pressure hybrid system;

3.48VBeltStarterGenerator (BSG) is an easy replacement for the original 12VBeltStarterGenerator, which can be matched without major changes to the design. And reduce the difficulty of matching, but also reduce the cost and weight compared with the high-pressure system

4. It can electrify high-load accessories on traditional engines, such as air-conditioner compressors, cooling water pumps, vacuum pumps, etc., to reduce the load of the engine, even if the engine is off, these devices can work; can support more power Car Equipment.

5. Increase the working voltage of the vehicle electrical appliance to 48V, which can further reduce the loss and reduce the outer diameter of the wire harness; the BSG/ISG ignition time is shorter, lower noise and less vibration.

Disadvantages:

1. The voltage rise, the electromagnetic compatibility requirements will be higher;

There will be an arc under 2.48V voltage, which is a risk hazard and needs to be handled;

3. The migration of the original 12V vehicle equipment to 48V requires redevelopment and testing, which is costly and has a long cycle;

4. Higher cost than 12Vstart-stop system, energy saving effect is not as good as high-pressure hybrid system.

48V light mixing system working mode

Automatic start/stop (START/STOP): Wait for the traffic light. When the vehicle is at rest, the engine is off. The 48V large-capacity battery uses the stored energy to maintain the normal operation of the vehicle electrical system. The engine can be started quickly at any time.

RECUPERATION: Energy recovery converts kinetic energy into electrical energy and stores it in the battery. Only the energy recovery function can reduce fuel consumption by about 7%.

Power assist (BOOST): The hybrid system can reduce the displacement of the engine. During the speed-up phase, the auxiliary power of the motor can make up for the lack of engine power and reduce emissions without losing power.

SAILING/ACTIVEENGINE-OFFCOASTING: When the vehicle is running at a constant speed and the battery is fully charged, the engine fuel injection system is turned off and the motor is used to maintain the vehicle operation. The power provided by the motor is used to offset the running resistance and the drag resistance of the engine. The BSG/ISG at the P2 position can separate and shut down the engine during high-speed cruise, with enough power to keep the vehicle cruising. When the accelerator pedal is pressed again, the engine will start quickly and smoothly cut into the current speed.

COASTING: When the throttle is released and the vehicle is in the coasting phase, the clutch separates the mechanical connection between the engine and the transmission system, completely shutting down the engine and achieving a longer driving distance. It is equivalent to the traditional vehicle neutral taxiing, except that after the traditional vehicle is switched to neutral, the engine speed needs to be injected to maintain the engine when it is reduced to idle speed.

Compared with pure electric and hybrid solutions, 48V micro-hybrid system change a little power drive system and can deploy quickly. It is a relatively low-cost and fast deployment solution. This is one of reasons it become popular now. For domestic car companies, despite policy, it will turn to development of electric vehicles and hybrids. But compared to strong mix of 200-600V, especially current strong mix of Ralink and Corolla is now only sold for 13 or 40,000. If cost continues to compress, 48V market will be very big especially from application development to final mass production market, it is necessary to wait until new energy vehicles occupy a certain proportion market. This needs whole industry chain, not only development of technology of car itself, but also require construction of infrastructure and capacity production.

The page contains the contents of the machine translation.