Low speed electric vehicle safely arranges lithium battery pack.

For low-speed electric car industry, although the final specific standard terms are still in controversy, but the first year of 2017 will become the standard of low speed electric vehicles, should be no doubt about that.

Deal with the fact that the low-speed electric car manufacturers in addition to express my views to actively fight for position, more important is to against the standard may be the terms of the requirements, organization research, formulate and adjust the direction of the product platform and technical requirements, layout, prepare in advance.

There are two main line, in the draft standard "meet safety requirements" and "use lithium battery". In this paper, combined with the technical characteristics of pure electric vehicles, analysis in order to meet the safety requirements, low-speed electric cars and car body power battery arrangement of the technical problems needs to be addressed.

Background

Pure electric vehicle safety systems involving collision safety, electrical safety, functional safety and security, maintenance, security system components as shown in the figure below:

Low-speed electric car security arrangement lithium battery pack key point must be considered

After low-speed electric cars in the draft standard for collision safety requirement is:

1) vehicles at 40 km/h speed (cars for 48 km/h), carried out in accordance with the GB/T31498 frontal crash test, collision results meet the provisions of GB/T31498 and GB11551.

2) vehicles shall be carried out in accordance with the GB/T31498 side touch, collision results meet GBT31498 and GB20071.

Low-speed electric car security arrangement lithium-ion battery pack must consider the key point

Therefore, to ensure the power battery and related electrical parts can reach safety requirements after the collision, important to discuss analysis from the following three aspects:

1. The bearing power assembly, power battery body assemblies;

2. Power assembly, power battery installed parts of the body assembly;

3. Power battery assembly structure.

In addition, the protection of contact and to reduce the secondary accidents is low speed electric safety standards must take account of the factors.

A key: the formation of multiple power battery protective body structure

By any kind of modern car powertrain, chassis, body and on-board network of four big assembly, including the structure of automobile body assembly, body structure is essential to the vehicle safety and empty quality.

Most low-speed electric car manufacturers are traditional automobile structure, such as common in the market "rushing" model, is conducted on fuel oil money rushing body structure changes.

A typical use of lead-acid battery low-speed electric car body structure is as follows:

Low-speed electric car security arrangement lithium-ion battery pack must consider the key point

Because of the limitation of traditional vehicle structure based on its use as the low-speed electric assembly or as a whole, or is divided into many blocks in the car before the position such as warehouse, under seat, backup tire warehouse, damaging to the whole structure.

Low-speed electric car security arrangement lithium-ion battery pack must consider the key point

For now, the main change is the change of low-speed electric car cabin internal layout of the components, compared with traditional body, powertrain occupies less space, collision of dummy chest damage index is bigger. To ensure the safety of the collision effect, can consider to increase the deformation energy absorption area vehicle energy absorption intensity.

As a result of the pure electric vehicle passive safety depends largely on the degree of protection of power battery, so pure electric car body in addition to need to take personnel safety protection, more importantly for power battery protection.

The sustainability of the long run, to ensure low-speed electric car research and development and industrialization of technology, it is necessary to the development of a new platform and redesign the structure of the vehicle, is used to guarantee the safety of the vehicle. In order to maximize prevent vehicles in collision damage, power battery in pure electric vehicle body design, the development is best used when multiple protective structure. Multiple body below for Nissan Leaf protective structure:

Key 2: powertrain and decorate a form of power battery

1. The power battery arranged at the site of the highest vehicle safety

The safest parts of the battery installed between two longitudinal beam frame and rear axle before and after the front axle, to a great extent, can reduce or prevent from before and after, left and right hand side collision damage.

Such as FSV car battery originally designed a T glyph, configuration on the rear axle in 2 between the wheel and the exhaust passage. After collision simulation test has proved that the battery may be damaged during collision, so instead I glyph, it in the exhaust passage. To meet the frame "between two longitudinal beam and rear axle, front axle after" requirements, as shown in the figure below.

Low-speed electric car security arrangement lithium-ion battery pack must consider the key point

Nissan Leaf's overall arrangement also abide by the "battery installed between two longitudinal beam frame and rear axle, front axle after" this principle, as shown in the figure below.

Low-speed electric car security arrangement lithium-ion battery pack must consider the key point

If after the collision, the first to hit the rear bumper - frame - spare tire, the second is the belt wheel axle, impact energy after a big cut to the battery.

2. The powertrain is decorated in protection have rigid frame structure

Powertrain installed in the body parts and forms of optimization, for performance, especially the security to significance. Such as the Nissan Leaf E powertrain (including drive motor + 5 CVT metal belt type stepless transmission + battery management system (BMS + high voltage insulation shielding electric wire/cable) is installed in a pair on the frame, inverter with aluminum alloy die casting shell on the installation of the frame on the top of the drive motor, thus get reliable protection.

3. The power battery is best placed from the crew compartment

Passenger cabin and the best power battery with steel plate separation, so that we can better ensure the passenger cabin crew does not collide with high voltage power system (including power battery) contact. Nissan Leaf is to make all the high voltage of high voltage power system and the system components are arranged in the body under the floor, at the same time ensure that when a collision, high-voltage electric power wire clamp. As shown in the figure below:

Low-speed electric car security arrangement lithium-ion battery pack must consider the key point

Point three: power battery assembly form

Power of fuel in the car battery is equivalent to the traditional internal combustion engine, the fuel needed container -- fuel tank, so power battery container as well. In traditional auto layout design, the installation of fuel tank in the body has a strict request: no matter from which direction the impact, only allow fuel tank rotation, will never allow fuel tank deformation. This requirement is also suitable for pure electric vehicle power battery assembly (including power battery Pack + power battery holder + power battery management system (BMS + encapsulated power battery container).

Nissan leaf power battery assembly container appearance and structure as shown in the figure below:

Low-speed electric car security arrangement lithium-ion battery pack must consider the key point

The Leaf of power battery and power line beam and BMS battery management system are installed in the water tightness of "battery containers made of steel sheet stamping, not only can ensure the vehicle collision, power battery, power line beam and BMS system is not damaged, and can ensure the driving rain and a certain depth of shallow wading driving safety.

Point four: protection and other contact

1. Direct contact with protection

Crew directly touch the batteries and other high voltage power system components (including DC/DC booster, DC/AC inverter, main beam/high voltage insulation shield of power cable and plug) will lead to electric shock, so they must be protective coat/barrier (including rubber and plastic insulation, metal mesh barrier closed shell, etc.) protection, avoid direct hit a crew. The most important is the protective device shall not be in the case of unused tools is opened, dismantled or removed. Below for the leaf maintenance plug Settings:

Low-speed electric car security arrangement lithium-ion battery pack must consider the key point

2. To prevent secondary collision accident

Use lithium battery low-speed electric cars and electric cars, existence follows after collision electrical safety hidden trouble, easy to cause the secondary accident: power system components of high voltage insulation shield, insulating sheath damage, leakage caused by crew, directly or indirectly, to get an electric shock; Power battery touch, injury or damage to the battery internal short circuit or leakage caused overheat, smoke, fire, or caused by charging overheat, smoke and fire.

In the actual crash test results, however, the low speed electric vehicles will be able to give you advice on the following arrangement:

(1) The power battery box layout as far as possible in the vehicle collision deformation energy absorption area, especially prone to explosions, fires lithium ion batteries in order to avoid extrusion deformation in the collision.

(2) Power battery box body longitudinal beam fixed way make use of and solid connection, such as monomer battery can use independent stable fixed frame type structure as a whole.

(3) The circuit layout should be connected with the deformation of car body structure as far as possible, strengthen the insulation protection of high pressure at the same time.

The page contains the contents of the machine translation.