Key technologies and advantages of automotive 48V battery system
Recently, Hitachi developed a 48V lithium-ion battery pack for high-power output of small-displacement vehicles for medium-heavy vehicles. Due to its good system performance and high cost performance, Hitachi is expected to become popular in China and Europe. The 48V system currently on the market is mainly used for micro-hybrid and weak hybrid vehicles. The lithium-ion battery pack developed by Hitachi has further developed the application of 48V system in the field of hybrid vehicles.
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48V system concept
In order to more effectively save energy and reduce emissions and improve fuel economy, people have found a new system between the engine itself and a new power system, which is a hybrid system. Nowadays, the oil-electric hybrid system is commonly used, that is, in the car of a diesel engine, plus an electric motor, the two engines work together. The original micro-hybrid system was equipped with a belt drive starter motor (BSG) on a starter motor (typically 12V) on a conventional internal combustion engine. The motor is a Stop-Start integrated motor that controls the start of the engine. And stop, thus canceling the engine idle speed, reducing fuel consumption and emissions, that is, the 12V micro-hybrid system, with automatic start and stop function.
The 48V system is an improvement of the 12V micro-mixing automatic start-stop system. The system voltage is 48V. The power-type lithium-ion battery with less than one-degree power is used to replace the traditional lead-acid battery, and the BSG motor is used to replace the traditional starter motor and generator. It is equivalent to an enhanced version of the automatic start-stop system. In addition to the automatic start-stop function, it can also provide auxiliary power when necessary.
Source of 48V system
The concept of the 48V system was first derived from several German OEMs including Audi, BMW, Daimler, Porsche and Volkswagen in 2011 and developed the LV148 standard. In June 2013, the European Union approved the 2020 CO2 emission standard, which requires the average carbon dioxide emission level of new vehicles to be controlled at 95 g/km by 2020; European automakers will face if they fail to meet the CO2 emission limitation requirements in the future. A fine of up to 95 Euro per gram per car. This mandatory standard has prompted OEMs and component suppliers to reduce the fuel consumption of vehicles from different technical routes. The 48V system has become a focus of attention in the industry due to its significant cost savings and emission reduction.
Advantages and key technologies of 48V system
Infineon believes that the development of the 48V system is based on the following:
Although 12V start and stop is low cost, CO2 emission reduction is limited;
High-pressure hybrids reduce emissions, but system costs increase more;
48V to start and stop the system at a cost close to 12V;
Provides near-high-pressure hybrid technology performance;
CO2 emission reductions can be up to 15% or more;
The system cost target is less than 1000 Euros;
A load other than the power system can be provided for a more advanced and energy efficient design.
Compared with the advantages of the 12V micro-mixing system, Hong Yinglin, the new energy product manager of Delphi Packard Asia Pacific, gave us an example: “For example, air conditioning, when the traditional car is waiting for the red light, the engine is at idle speed, the belt-driven air conditioner compressor can Continue to work, air conditioning still cools. But for cars with start-stop function, when you need red light, you need to switch to electric air conditioner, otherwise passengers will have to endure the red light or traffic jam when there is no air conditioning environment. An electric air conditioner compressor The power is at least 2.5kw. If you use 12V power supply, the power grid will be unbearable. There is no problem with 48V. In addition, the 48V side can also supply active suspension, electric steering, electric heater and other power supply."
At present, the mainstream in the Japanese market is a strong hybrid vehicle equipped with a high-voltage battery of 100V or higher. The lithium-ion rechargeable battery module of 100V or more is used, which can greatly improve the fuel efficiency of the hybrid vehicle (HEV), but the special components. And the pressure component is costly. Using a 48V system will also increase the cost, but compared to the cost of a pure electric car or a strong hybrid car, the 48V system can save 40% to 60%, and the 48V lithium-ion rechargeable battery module can also increase 10 to 15%. Fuel efficiency.
One of the keys to the 48V system specification is lithium-ion battery technology. Lithium-ion battery technology provides higher (3 times) energy density than lead-acid chemical batteries, and is reduced in size and weight. The 48V lithium-ion battery has better charging performance and can store the car brake recovery energy more efficiently, which is more and more electronic load required in the car (such as front seat heating, heatable windshield, rear The shock absorber) provides more power.
Application Status of 48V Lithium Ion Battery System
One of the keys to the 48V system is lithium-ion battery technology. Lithium-ion batteries have higher energy density and better charge and discharge performance than lead-acid batteries and nickel-hydrogen batteries. Lithium-ion battery cells have a voltage of up to 3.7V. In order to meet the voltage requirements of electric vehicles, it is necessary to form a battery pack in series and parallel to meet the high-energy and high-power conditions required for electric vehicles. Under normal circumstances, the car power system will regard the battery pack as a single battery. During the start and stop of the car, the entire battery pack undergoes frequent charging and discharging processes. The battery pack is made up of monomers. It does not guarantee the absolute consistency of the battery cells before leaving the factory. If one battery in the battery pack passes through multiple charging/discharging cycles, its charging state cannot be periodically balanced with other batteries. Will eventually enter a deep discharge state, resulting in damage and eventually forming a battery pack failure, so we need a battery detection system (BMS) to monitor the overall measurement of the battery pack and individual batteries, including voltage, current, Charge state, etc., and replace the single battery in time to extend the battery life and service life.
The new 48V lithium-ion battery pack developed by Hitachi is equipped with BMS boards, battery cells, relays, and fuses in the same box. It has high assembly and high reliability. This battery pack can accelerate and decelerate in vehicles. It also supports efficient operation of hybrid engines and motors in various situations, such as energy regeneration during braking.
At present, the 48V lithium-ion battery pack on the market generally consists of 12~13 single cells, which are mostly used in small pure electric vehicles such as electric bicycles, electric motorcycles, electric tricycles, etc., as well as power tools; main vehicles Lithium-ion power battery manufacturers include AVIC Lithium, CITIC Guoan Mengli and Wanxiang Group.
In the field of hybrid vehicles, the 48V lithium-ion battery system is mainly used in micro-mixed or weak-hybrid systems, and is in the research and development and limited production level. Under the requirements of developing more energy-efficient automotive products, car giants are developing automotive products that use the 48V automatic start-stop system. IHS, the world's leading industry research organization, released a report that by 2025, 48V mild hybrid vehicles will account for more than half of all hybrid vehicles, and 95% of mild hybrid vehicles will adopt 48V.
The 48V lithium-ion battery pack developed by Hitachi can be applied to medium-duty hybrid electric vehicles with higher input power and output power, and the battery cells have excellent performance in low temperature resistance. The output density is the previous Hitachi battery unit. 1.5 times, with good fuel consumption reduction and high cost performance, it has promoted the popularity of Zhonghe Automobile in China and Europe.
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