● electric vehicle battery
By the previous lecture, presumably you have already classified electric cars have a certain understanding, but if you want to buy electric cars, only to understand how to divide their category is clearly not enough. Battery as a power source for electric vehicles, electric vehicles have been regarded as an important indicator of the development of technology, but also an important bottleneck restricting the development of electric vehicles, and its performance is directly related to the length of the vehicle mileage, and therefore have some battery basic knowledge related to the purchase of electric cars in the future will be of great help.
● Battery Categories
Broadly speaking the main battery from the battery can be divided into chemical, physical and biological cell battery three categories, including physical and chemical batteries have been used in mass production battery electric vehicles, and bio-battery is considered an important future development of electric vehicle batteries one direction. For the practical application of the current situation of consideration, we are only physical and chemical batteries battery details, should you also have interest in biological cells, can further refer to other materials.
■ Battery Chemistry
Chemical battery electric vehicles are currently the most widely used types of batteries, such as nickel-metal hydride batteries, lithium ion batteries, lithium polymer batteries, fuel cells belong to this category. From a structural point of view, which may be further divided into two major categories of batteries and fuel cells, we now see the vast majority of electric vehicle battery technology are used to drive, such as the Toyota Prius, Tesla MODEL S and the like. Of course, here we are talking about the battery is not talking about everyday car battery, but the rechargeable battery collectively, lead-acid batteries commonly used in which the car battery is only a segment categories.
■ Battery Chemistry
Chemical battery electric vehicles are currently the most widely used types of batteries, such as nickel-metal hydride batteries, lithium ion batteries, lithium polymer batteries, fuel cells belong to this category. From a structural point of view, which may be further divided into two major categories of batteries and fuel cells, we now see the vast majority of electric vehicle battery technology are used to drive, such as the Toyota Prius, Tesla MODEL S and the like. Of course, here we are talking about the battery is not talking about everyday car battery, but the rechargeable battery collectively, lead-acid batteries commonly used in which the car battery is only a segment categories.
Qichezhijia
As the electric car battery more categories, much of which has been eliminated by the market and its great length to explain the obscure principle does not bring much help to the actual car, so we first through a table overview of these batteries types and basic characteristics, and then on the market several common battery described in detail.
Note: Since many cell types, so we list only some of the categories include representative.
Analysis of electric vehicle batteries
Type Weight energy density
(Wh / kg)
The nominal voltage of the battery cell (usually)
safety
Theoretical cycle
Life (times)
Commercialization representative of the vehicle
Lead-acid battery is good for about 30-50 2V 500-800 OBSOLETE -
50-60 1.2V nickel-cadmium batteries have been eliminated preferably 1500-2000 -
70-100 1.2V NiMH battery 1000 is now good use cash Prius
Lithium-ion battery lithium manganese oxide
100 3.7V battery preferably 600-1000 Obsolete early Prius
Lithium cobalt oxide
Battery 170 3.6V differential 300 Obsolete Tesla
Roadster
Lithium iron phosphate
1500-2000 100-110 3.2V battery good now using Teng potential
Three yuan lithium
200 3.8V battery is poor now use 2000 Tesla
MODEL S
Common chemical batteries for electric vehicles:
- lithium battery
Lithium battery electric car is one of the most common types of batteries, although from its inception in 1970, the time is not long, but with a high energy density, long cycle life and other characteristics quickly occupied the vast majority of electric vehicle battery market part of country. Today, in the sale of electric vehicles with lithium batteries mainly have two kinds of lithium iron phosphate and lithium three yuan, and these two cells there are significant differences in the characteristics of its own, so we need to be some careful explanation and Compared.
Why lithium iron phosphate safe?
Qichezhijia
For electric vehicle battery, most people probably have little knowledge, therefore, we wish to give an example to help you understand. Recently, BYD Daimler joint venture set up with a new electric car brand Teng potential upcoming sales, but they carry is the lithium iron phosphate batteries. Compared to earlier lithium manganese batteries, lithium iron phosphate is not much difference in the energy density of about 100-110Wh / kg, but its thermal stability is the best vehicle to use lithium batteries, when when the battery temperature is 500-600 ℃ high temperature, its internal chemical composition began to break down, and belong to the lithium cobalt oxide lithium at 180-250 ℃ when he had internal chemical composition in an unstable state. In other words, the safety of lithium iron phosphate lithium battery in none, because of this, it has also become one of the main categories of the current electric vehicle batteries.
Tesla Why three yuan lithium battery?
Compared with lithium iron phosphate, Tesla MODEL S using ternary lithium on weight much higher energy density of about 200Wh / kg, which means that the same weight ratio of lithium iron phosphate ternary lithium mileage longer. But its disadvantages are also obvious, when the self temperature 250-350 ℃, the internal chemical composition began to decompose, so the battery management system made high demands, the need for each battery separately installed safety device, in addition to Since the monomers are small, so the number of battery cells to very large bicycle to MODEL S, for example, the section of more than 700,018,650 three yuan lithium battery assembly in order to meet the amount of a car, which undoubtedly is the battery management system further increased the difficulty of control. Therefore, the current market in the sale of cars, only the use of a Tesla is a ternary lithium battery.
- NiMH battery charge and discharge control more focused
NiMH batteries are present, except the other mainstream electric vehicle lithium battery type, to the gradual development of post-1990s to open, such as the Toyota Prius as the representative of a lot of hybrid cars such batteries are used as the energy storage element. Common energy density lithium batteries gap is not large, about 70-100Wh / kg, but due to the cell voltage is only 1.2V, a lithium battery is 1/3, and therefore the demand at a certain voltage, which lithium battery pack large size than some.
Like lithium and nickel-metal hydride batteries require battery management system, but pay more attention to its battery charge and discharge management. The reason why there is a difference, primarily because of the nickel hydrogen battery has a "memory effect", that is, the battery capacity during charge and discharge cycles occur decay, excessive charge or discharge, are likely to exacerbate the loss of the battery capacity (this lithium battery item characteristics almost negligible). So for manufacturers, nickel-metal hydride battery control system will take the initiative in setting on to avoid excessive charging and discharging, such as battery charge and discharge control in a certain range of artificially percentage range of the total capacity, in order to reduce the capacity of the decay rate.
- Fuel cell car is the best energy future
In fact, the fuel cell is not a "battery" more precisely, a large power generation system. Due to its high energy conversion efficiency, pollution-free, long life and smooth running characteristics is widely recognized as the best future energy vehicles. In simple terms, the fuel cell is a chemical reaction converting chemical energy into electrical energy a device, and the main source of energy by continually supplying fuel and oxidant produced.
In theory, the type of fuel used in the fuel cell can be a lot, and even the traditional internal combustion engine can be used for fuel, but can really play electrochemical reactions, is just one of the hydrogen and oxygen in the oxidant, therefore, the hydrogen fuel cell is the fuel Research on core battery.
On the market today, the fuel cell vehicle not far from us. As previously reported, the world's first mass-produced fuel cell vehicles Toyota FCV will be held in March next year officially on sale in Japan. The car is equipped with a high-pressure fuel stack two 70MPa, the output power of 122Ps (90kW), mileage up to 700km (Japan JC08 conditions). In addition, the added fuel just three minutes, compared to a traditional electric vehicle charging time is a lot faster. Currently in Japan associated with various policy tight Luo clouds to have been drawn up, but when they can buy a home is still unknown, we had only to wait a long time.
Qichezhijia
■ physical battery
Physical battery as the name suggests, is to rely on to provide a physical change, energy storage batteries collectively, such as super-capacitor, flywheel batteries belong to the family members of the physical cell.
- Ultracapacitor power density but small battery capacity
Supercapacitor is a cross between traditional capacitors and batteries power elements between which rely mainly on the electric double layer capacitor and redox false charge storing electrical energy, chemical reaction does not occur during, so it is classified as a category of physical battery. Compared with the previously described chemical batteries, super capacitor three obvious advantages, first of all, the repeated charge and discharge hundreds of thousands of times (conventional chemical batteries, only a few hundred to several thousand times), on the life of a lot higher than chemical batteries ; secondly, the super capacitor during charging and discharging of the high power density, the moment can release a lot of energy to meet the electricity needs of a broader vehicle; and third, a better ability to adapt to the work environment is usually the outdoor temperature at -40 ℃ -65 ℃ when it can be stable normal operation (conventional batteries generally -20 ℃ ~ 60 ℃).
Of course, the advantage will be insufficient, the low energy density ultracapacitor development is restricted primary bottleneck, so at present it is mainly used in vehicle start system, and a small amount of military buses, as to whether the use of power supply can be used as a family car, the need Once the energy density of a breakthrough before identifying problems.
- Flywheel batteries are currently only as an auxiliary battery
Flywheel battery is put forward in the 1990s, a new battery concept, also belong to a physical battery. It is simply to produce energy using the principle of rotation of the flywheel when similar realize their charge and discharge. In October 2010 American Le Mans Series final round, the Porsche 911 GT3 hybrid cars on the first official use of flywheel battery technology, while the Porsche 918 Spyder is famous predecessor. But these two models flywheel batteries are only used for auxiliary energy use, its function is similar to our common brake energy recovery system. Even so, we still have reason to believe, as technology continues to develop and further reduce the price, flywheel battery prospects will be very broad.