Electric vehicle new technology 48V power supply-Lithium - Ion Battery Equipment

Electric vehicle new technology 48V power supply -Lithium - Ion Battery Equipment

At present, the design of hybrid electric vehicles (HEVs) and pure electric vehicles (EVs) is very attractive, but there is also a less obvious but significant development trend in the automotive industry: adding a 48V DC bus to the power system. 48V is not only suitable for hybrid vehicles and pure electric vehicles, but also for more ordinary internal combustion vehicles. It can be seen from Figure 1 that the market share of pure electric vehicles and hybrid vehicles is growing.(Lithium - Ion Battery Equipment)

Engineers and auto mechanics have been exposed to the ubiquitous 12V battery and auto parts since childhood (this is the industry standard with a history of more than 100 years), but they do not need to worry that the 12V system will not disappear soon. However, in the foreseeable future, the 12V system may co-exist with the 48V system.

What are the unique features of the 48V system? From the perspective of electricity, the answer needs to go back to Ohm's law, the physical laws related to voltage drop (V=IR), power (P=IV) and loss power (P=I? R). Although the voltage drop (loss) increases linearly with the current, and the power loss increases with the square of the current, the transmission power needs to be determined by the current and voltage. In short, more power needs to be output at a given voltage, and the greater the current, the higher the voltage drop, Power loss is also not recoverable.

This is not a new development direction. The solution providers in the electric power field have been familiar with this for a long time, which is why they use higher voltage. They seek better solutions to power the street lamp system, homes and industrial sites. But for cars, it is a good compromise to obtain 12.6V (nominal value) voltage from rechargeable lead acid batteries, which can take into account volume, capacity (ampere hours), cost Life, safety and other factors.

However, cars today need more power than cars a few years ago. In addition to the basic functions such as engine, light, radio, electric sunroof, electric power steering, network and information entertainment, many other safe and convenient functions will be integrated. These functions are usually included in the Advanced Driving Assistance System (ADAS). ADAS system has higher requirements for batteries and requires more power, Therefore, using 12V power supply to supply power to various core components and peripherals will cause greater current, while maintaining IR drop and I? The method for R power loss at an acceptable level is to use thicker wires, more copper materials and larger connectors, which in turn means that the cost and volume will increase and the vehicle system will become more crowded.

Is 48V power supply a new 12V form?

After a lot of analysis, the industry has decided to use 48V as the new power supply system. Unlike the traditional 12V lead-acid battery, 48V battery uses lithium battery, which has higher weight and volume energy density. It is known as "mildHybrid".

In this method, the 48V battery - as specified in the automobile standard LV148 - is used as a supplement in combination with the 12V lead-acid battery (which can provide 3KW rated power), as shown in Figure 3. 12V battery and 48V battery will be used together with their power distribution harness. When power output is required, both batteries will provide energy output. For example, 12V bus can provide power for ignition, lighting and infotainment systems, while 48V bus will be responsible for chassis control system, air conditioning, suspension adjustment, brake energy recovery, driving electric supercharger and turbine.

Consider a basic component: how to change the basic architecture of the engine starter when starting the starter and 48V battery, so as to better enhance the starting and stopping effect. This method is conducive to reducing the fuel consumption at traffic lights and parking and waiting, and further enhancing the fuel efficiency. In most cars with only 12V batteries, the battery provides power for the starter, and the alternator acts as the charger. However, the combination of 48V and 12V can provide up to 10KW of power. The starter motor and independent alternator are replaced by an integrated starter generator (ISG) or a belt starter generator. The 48V lithium ion battery and two-way DC/DC converter will be packaged in a solid box, which is actually a weak hybrid power system, Work with internal combustion engine. It can provide two thirds of the benefits, but only one third of the cost, while the economic benefits increased by 15% to 20%.

At the same time, choosing 48V also raises two questions: Why not change from 12V to 24V directly? Since higher voltage can bring more benefits, why limit the voltage to 48V? There are many different answers to these questions.



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