How small battery what are behind the doorways became the bellwether of the electric car industry?
Battery is the electric car "heart".Since the electric car development, all kinds of technical route with flowers, debate.One of the most widely lithium ion batteries used in it, there are three yuan, lithium iron phosphate, lithium manganese acid and various technical route to coexist.Lithium ion batteries are divided into square at the same time, the soft bag, the cylindrical structure of three kinds of forms.
And the more the ramifications are, the more represents our continues to explore, represents the electric car eagerly look forward to: electric cars need a powerful "heart".
To the requirement of battery pack
For the core of the electric car - battery, we asked its safety, high energy density, long life, charging time is short, and performance is remarkable, and so on.A a request, and this seems harsh, but notting have is not the electric car to realize industrialization and hard Numbers.
The contrast is the standard for electric car battery?What is a superior performance?There is no doubt that lithium ion batteries as its basic unit, it is very important for the advantages and disadvantages.
But we pay most attention to safety, take batteries, safe, the battery pack is safe?
We can see that in 2002, the lithium iron phosphate (LFP) Valance company industrialization by the United States for the first time, then caused the extensive concern of the Chinese market.Since 2004, was an investment in our country the
lithium iron phosphate material and lithium iron phosphate power battery, the lithium iron phosphate is relatively stable, higher security.Then, it become the main lines of the anode materials, dispute to paragraphs.
But as the tesla used in power battery nickel anode materials for lithium cobalt aluminate, argument again.Its low energy density, lithium iron phosphate has its disadvantage.
Since 2014, according to the survey found, into the domestic lithium battery cathode material industry as a whole appeared to the trend of the ternary material transfer, downstream of the battery is basic in the development of the ternary material of batteries, also leads the upstream materials enterprises began to intensify the development and production of ternary material.
And a series of change, also is precisely the lithium electricity industry in slowly groping, slowly mature.Such as the safety of a battery pack, batteries safe alone is not enough, it must rise to the hierarchy of a system.That is to say the safety of the battery pack, by the whole battery system, rather than just a single element.
What's more, a safe, reliable, high performance battery pack, but also involves the coupling of the multidisciplinary knowledge, the more need to achieve a perfect and reliable system.Just as the plane is considered to be the safest means of transportation, not only is "safe" engine, the structure of "security" can guarantee, which also the integrated use of the artificial factor analysis, software security, risk
management and quantitative risk assessment and other advanced technology to prevent the accident, can be said to be the system to ensure safety.
Below we from battery system out of its core components a battery module, talk a different module structure.
About the battery module
The battery module can be understood as lithium ion batteries by way of series-parallel combination, and adding monomer battery monitoring and management unit.Battery module structure design, often can decide a battery pack performance and security.Its structure must support, fixed and protective of batteries.At the same time how to meet the requirements of over current, current uniformity, how to satisfy the control of the temperature of the batteries, and can have serious abnormal blackouts, avoid a chain reaction, etc., will be a standard to judge the performance of the battery module.
But with the development of electric vehicles, and the pursuit of performance, thermal management is becoming the battery module design of a crucial link.Natural cooling have already can't meet our requirements.Air cooling is due to its low efficiency, and the temperature consistency of batteries are harder to control, and performance.High performance requirements of the battery module, therefore, its thermal management solutions have turned to surface or phase change materials.The following will introduce all kinds of different structure module design of batteries.
Square battery module
Square batteries can be said to be the power battery car, most used batteries.The shell made of aluminum, steel, and plastic.The thickness of batteries is the thickest in three kinds of structure, thus has its internal and external surface temperature difference is bigger.The module structure is more for natural cooling and air cooling structure.
Let's take a look at the BMW I3 battery module design.
We can see that the I3 battery module from the structure has a high performance elements needed for the module, and a high-performance electric vehicle, is by the details of each place in common.The heat dissipation, mean temperature and reliability and so on, of course, it remains to be the market validation.
Battery module (bring the I3 squares)
Its batteries is BEV2 VDA standard specification, for 1 p12s module combination, was surrounded by thick aluminum plate fixation.Aluminum plate by welding together, and will be collected from the control panel installed on the side of the module.
The module structure is very strong, but at the same time is also sealed.High-voltage electrical connection between module and module in the form of wire, and develop the connector, convenient plug.At the same time, no strong wire or gathering line are adopted at present more reliable, contact resistance smaller ultrasonic welding and connection to connect.The connector is connect with the method of laser welding and batteries.
The NTC is fixed on the connecting piece for the collection of temperature.Is completed, the surface with a blister tray cover protection.Can see, the module, complete structure is very strong, reliable, and all the connections are more orderly.
And, of course, the key point, batteries, thermal management.
I3 module design is through the flat at the bottom of the thermal
conductivity.Module bottom and install the bottom part of the battery contact cooling pipes, and cooling duct is refrigerant.The design of cooling pipes can be spread in the bottom of the box body, its structure is simple and reliable, suitable for mass production.
Battery module (bring the I3 squares)
Soft package battery module
Soft package of batteries, battery pack, as well as the recent popular a kind of structure type, its use in electric vehicle is more abroad.
Soft package of batteries physical structure determines its not easy explosion, generally only the shell can withstand the pressure is high enough, can be Fried, and internal pressure a soft package of batteries, aluminum-plastic film edge will start pressure, discharge.Soft bag batteries is also in the structure of several kinds of batteries at the same time, the best heat dissipation.
On market at present, most of the seller is nissan's Leaf, the module structure is completely sealed, does not take into account the cooling, neither heat dissipation.
And Leaf frequent feedback capacity attenuation too quickly in the market, also has to do with the thermal management.Obviously along with the people for the pursuit of high-performance electric vehicles, forcing soft package of batteries must also have the active thermal management structure.
Let's look at a World meets booth liquid-cooled soft BaoMo group.Its module composed of batteries cascade, and batteries have interval between configuration of surface plate, its guarantee each batteries have a bedding face comes into contact with the surface plate, and give full play to the advantages of the soft bag batteries cools.
(bring liquid-cooled soft package battery module)
Soft package of batteries will, of course, liquid-cooled mature technology also is not easy, it must consider the surface plate fixed, sealing, insulation and so
on.Reliable electrical connections at the same time, and with "fuse" structure connection piece, this is the direction of high performance soft BaoMo group.
We can see soft package batteries after its cooperate to improve the module structure, the advantages will be highlighted.
Cylindrical battery module
Cylindrical batteries is in all kinds of electronic products, the most widely used structure.Today, also must share in the electric car industry.The most typical is 18650 batteries, its craft after years of precipitation, and under the condition of large-scale automated production, today belongs to the most mature, stable and consistent the best batteries.
And cylindrical batteries, but also has the highest energy density of the third yuan material batteries can achieve 210 ~ 210 wh/kg.Domestic at present, a lot of cylindrical battery packs for natural cooling or air cooling structure, its effect is not satisfactory.
Let's take a look at, the cylindrical batteries pushed to the forefront of tesla battery module.
Believe that there have been many people met tesla's module:
Of a tesla motors need to be more than 7000 18650 batteries, a module, you will need to more than 400 batteries, at the same time to high performance goals and to integrate many functions in the module, the workload and the difficulty of visible.Among them, even using some cross-industry technology, make the person shine at the moment, die for it.Such as "fuse" design of the batteries connected.
Can say, in the battery industry, but very few people can imagine, this perhaps is a distance.While the application of this technology greatly improves the safety performance of the battery.At the same time, surface pipeline and the application of 18650 batteries greatly solve the heat dissipation and mean temperature, the performance and life of the battery is a great help.Not only that, the battery modules in the use of space size, more is calculated.
Here or want to admire the tesla would have a thing perfectly attitude, which is such a module, has become a high performance core components essential for tesla's battery pack.
(bring about tesla cylindrical battery module)
(bring about tesla cylindrical battery module)
The heart of the electric
Through some simple list above, we see not hard, no matter what the structure of the batteries, actually there is no shortage of some good application examples.For the lithium ion batteries, if as a revolutionary product, now there are still many shortcomings and limitations.But we rather than blindly wait for material development, consider more, how to make the battery module, battery system.That is what we create a powerful path to the heart of the "electric".