Tesla battery board dismantling: more than 7000 18650 batteries

2019-09-26  2015

The stylish shape, acceleration of 3.2 seconds per 100 kilometers and 440 kilometers of battery life are the data that the Tesla Model S presents to people as a pure electric vehicle.

Model S is able to have performance that is no worse than traditional fuel vehicles. In addition to motor technology, it also benefits from Tesla's advanced battery technology.

So, what is Tesla's unique achievements in battery research and development in one of the core technologies of electric vehicles?

According to reports, the Model S has a total weight of 900 kg and is placed in the chassis directly below the cockpit. It also provides energy for the motor while also stabilizing the center of gravity of the vehicle.

Recently, foreign cattle people have opened a Model S battery board to find out.

Foreign cattle people directly show us the battery pack. The battery pack houses the chassis position between the front and rear axles and weighs up to 900 kg. Therefore, the center of gravity of the chassis is low, which is very favorable for the high speed stability of the vehicle. The battery pack occupies almost all of the chassis of the vehicle, but the battery pack is not the main body of the bearing. The battery pack has the ribs and the force frame protection, which greatly reduces the explosion hazard during the collision.

The battery pack has a nameplate indicating its identity, which indicates that its capacity is 85kWh, 400V DC, and simply the battery can hold 85kW, which can be used by an ordinary family for one month.

The surface of the battery pack is not only protected by a plastic film, but also has a protective material for the fireproof material under the plastic film. Below the shield is the battery pack. The shield is bolted to the battery frame and the joint is filled with a sealing adhesive. The battery pack protection is good in appearance.

The Tesla Model S battery pack looks very tall. The battery board is made up of 16 battery packs in series, and each battery pack is formed by 444 lithium batteries in parallel. Therefore, the Tesla Model S battery pack consists of 7104 18650 lithium batteries.

The total fuse is located at the front of the battery version and has a housing to protect against impact. It uses Germany's Bussmann Basman, rated operating current is 630A, rated voltage is 690V, breaking current is 700-200kA, the fuse is made in India under the globalization trend. The market price is around 600 yuan.

The 16 battery packs in the panel are evenly laid on the housing, and the overall structure is compact, and the tiling is advantageous for heat dissipation. Each set of battery packs consists of six sets of single battery packs connected in series, but the arrangement of the single battery packs is not balanced, but irregular results are used. The guess is to facilitate the arrangement of the heat sinks in the battery pack.

The voltage across the panel was measured to be 313.8V and the cell voltage was 196.3V. Obviously this battery does not reach the rated output voltage, which may be caused by insufficient battery power.

Each battery in the battery pack has a fuse link to prevent the single battery from overheating and the overall battery overheating, and each battery fuse is very beautifully soldered. The battery pack is wired centrally to the battery control module. These lines are used to detect the voltage of the battery pack to ensure proper operation of the battery pack.

The battery pack is entirely covered by a transparent plastic case surrounded by metal heat shields on both sides. The thickness of the battery is slightly thicker than that of the sole of the foot, and it is a long-length battery pack, which causes the center of gravity of the vehicle to be greatly reduced. The overall battery pack protection is quite good.

The 18650 lithium battery is the lithium battery of an ordinary notebook computer. Many 18650 lithium batteries are composed of a single battery pack, and then the battery pack is composed of a battery pack, and 16 battery packs constitute a battery pack. It may seem simple, but it actually needs to solve a lot of problems with connection and cooling.

Each set of battery packs is connected in series by a 2/0 main line. The main line is located in the center of the panel and covered with a shield, which is more concealed. The 2/0 main line sinks the current and is connected to the contactor at the output. The contactors are manufactured by Tyco Electronics specifically for Tesla.

There is a 2/0 main line in the center of the panel, and each group of batteries outputs current through the main line in series, so the 2/0 main line is especially important. Tesla uses Champlain's cable for electric vehicles, which can withstand up to 600V and can operate between -70° and 150°. The 2/0 main line protection is quite good, not only with guard protection, but also with fireproof material wrapping. This can be guessed that it is possible to generate high temperatures during work.

In addition to the battery pack, the panel is at most a "coolant" line. Each set of batteries requires a certain amount of "coolant" to be supplied. Although the "coolant" does not have the pump to drive the active flow, all the pipes of the entire panel are connected, and the "coolant" can be expanded and contracted to flow in a certain range.

The "coolant" is green and is a mixture of 50% water and 50% ethylene glycol. The "coolant" is used in conjunction with the aluminum tube to maintain the balance of the battery temperature and to prevent the battery from degrading due to excessive local temperature. Tesla's battery thermal management system controls the temperature between the battery packs to ±2 °C. Controlling the temperature of the panel can extend the life of the battery.

The Battery Management System (BMS) is a device that performs safety monitoring and effective management of the battery pack to improve the efficiency of battery use. For electric vehicles, the effective control of charging and discharging the battery pack through the system can achieve the purpose of increasing the cruising range, prolonging the service life, and reducing the running cost, and ensuring the safety and reliability of the battery pack application.

The main functions of the battery management system include data acquisition, battery status calculation, energy management, thermal management, security management, equalization control and communication functions. As can be seen from the circuit diagram, the battery management system is developed by Tesla itself and has a high level of intellectual property. The system can handle charge and discharge and heat problems on its own. I believe that domestic manufacturers are harder to come out.

To sum up

This time, foreign cattle people dismantle the Tesla Model S and let us know more details. The number of 18650 is determined by the total capacity of the panel; the aluminum tube cooperates with the "coolant" to make the battery heat more balanced; and the complicated management of the battery management system BMS makes the battery charge and discharge perfectly.

In general, the Model S battery is quite well protected, the internal structure is well designed, and the battery management system is quite detailed. I believe that domestic independent brands want to have a lot of difficulties in the cottage.