Engineers explain battery management system where Tesla Motors

Lei feng’s network by the writer Ye Lei Ray, acting engineer.

(Tesla Motors,

Since the Model s listed depend on the already being disassembled numerous times, which also confirms the Tesla electric car from a side market’s benchmark status in the early.

| Powertrain components Hello Kitty case for iPad

Model s Powertrain is divided into the following sections:

Batteries for ESS

AC induction motor Drive Unit

Car charger Charger

High voltage power distribution box HV Junction Box

PTC heater heater

Air conditioning compressors A/C compressor

DC converter DCDC

Model s with three-phase AC induction motors and motor controllers, motor and gearbox integrated with one. Especially the motor controller is packaged into a cylinder, corresponding to the motor each other, looks like a dual-motor. From a design viewpoint high integration, symmetrical in appearance. Gear box in the middle of a fixed speed ratio (9.73:1) programme. 85KWh motor 270KW of peak power and torque to 440Nm.

Charging charging system supports three modes:

1, super fast charging DC charger

Super charging can be directly output 120KW ESS charge, less than an hour to fill.

2, high power wall charger

Under the rear seat has two car chargers, a master from. Main charger belongs to the default open, power: 10KW, almost 8 hours to fill. Slave charger hardware has been installed in the car, but need to pay an extra 18,000 to activate, can double the charging capacity. This type of hardware is already configured, server and IBM through license fees after the same. Tesla currently has turned the strategy used in the on battery power, 60 version actually installed on more than 70 degrees, set aside part of the full capacity just to avoid full to help extend battery life, so start with low Edition is a cost-effective choice.

3, 220V household outlet

Charging power 3kW fully charged for about 30 hours. Put the charger in the car, even where no charging infrastructure can also use ordinary household Plug and charge it with electricity.

Thermal management interesting is that Model s cooling system is implemented with a four-way switching valve of the series-parallel switch. The purpose of my analysis is based mainly on working conditions to select the optimal thermal management. When the battery is in low temperature when heating is required, motor cooling circuits cooling circuit in series with the battery, which makes motors for battery heating. When the battery is in high temperature, motor cooling circuit and battery cooling circuits connected in parallel, two independent cooling systems cooling. Thermal management is quite ingenious.

| Battery PACK

First look at the PACK without having to disassemble, outside there are 3 sets of interfaces. Low-voltage interface, high-voltage interface, cool interface, respectively, and using quick-plug scenarios. Indicates that Tesla designed battery system when considering the technical requirements for power mode, even now there is very little for electricity needs but this gene has always survived. High-voltage plug thick Pin in one hand played a role in positioning, as well as grounding, the finer the Pin used to achieve high-voltage interlock function.

Front PACK designed waterproof and breathable on the top valve, gases and liquids and dust particle number size differential, so gas molecules through, liquids, dust, not, so as to achieve the purpose of waterproof and breathable to avoid water vapor condensation inside the PACK.

Upper PACK a lot of screws, so that the white on the insulating pad with adhesive in the Pack, in addition to insulating fire prevention function, can also play a role in certain waterproof. PACK lid is tightly with plastic sticks, even removed all screws are still unable to open. Remember that in the summer we have seven or eight of the 14 people “break hard to pry” one hour to destructive opens. Thought Tesla at design time must have been holding the axe the sunk boat concept, had no intention of following the repairs, so natural and no manual maintenance switch on the PACK, just left a fuse replacement.

Tesla tray with aluminum as main bearing box-type frame, frame welding block aluminium plate on the bottom. Dismantling is a 85KWH with high version, the rightmost two Module stack. Both sides of the PACK features a lot of explosion-proof valve (85). Found in the process of dismantling in the PACK always use loose insulation Board to separate high voltage devices, fixing the insulation plate is usually the way glue, is made of dogskin plasters inside the PACK played the full patch, it is hard to imagine how such a complex process in the production process. Guess is considered early in the design of the inadequate follow-up was condemned by in a uniform manner.

BMS within the PACK is almost completely bare, perhaps to reduce weight, but they also bring a certain amount of risk.

Water cooling system using the parallel between the Module structure instead of in-line, the purpose of which is to ensure that the coolant flow into each Module has a similar temperature.

High-voltage electrical connections between the Module uses the staggered around the arrangement, rather than from the tail of the PACK to the top, and then back from top to tail this is simple way of connection. Guess is that in order to prevent the formation of large current loop to generate stronger radiation interference.

Current sampling only took a ISAscale Shunt at the industry level through the SPI bus to communicate with the BMU. Roewe E50 on A123 battery solution, which uses a shunt and Hall double backup measures. After all, the current value is a critical parameter in the ESS system.

| Battery Module

Due to the use of NCA batteries, Tesla is far ahead in the energy density, Pack energy density is higher than many models of the Cell section. Next figure with high and low with the difference in module, with low module each and 10 fewer cells, serial number is 6 strings, for battery management and therefore there is no significant difference. Busbar is connected and can be seen from the convergence Board parts of color is different, is the point on the surface treatment, prevent oxidation.

Module hot-swap design due to Tesla had 18650 battery will inevitably lead to the Coolant pipe must be designed to be very complex, and the battery is glued firmly fixed on the Module, no maintenance and the use of Echelon. And choose a square battery I3 and the Volt batteries and cooling the system integration.

Volt in each battery cell design the thermal 曡, the heat exchange area bigger is better, and speculated that this may become the mainstream in the future.

| The battery management system BMS

BMS client-server, the host controller (BMU) is responsible for high voltage, insulation, high voltage interlock and contactor control, external communications functions. From the controller (BMB) is responsible for the unit voltage, temperature detection, and reported to the BMU.

BMU has pair of MCU design, Deputy MCU detects the MCU operation, once the failure to obtain control. More humor on the BMU has a manual reset button, just couldn’t believe this is when car production ECU, more like a computer motherboard. Contactor pre-charge of the strong currents directly on the BMU is also a bold design.

Is Tesla, BMW under i3, A123 module control BMB’s comparison of the three. Specific parameters are as follows:

Legendary Tesla detect the battery voltage of more than more than 7,000 is only 74 batteries parallel detection point, legend control the temperature of each monomer, 444-battery with only two temperature probe points. Balanced legend each battery actually circulating current 0.1A only, for battery 230Ah bucket. Especially on the redundant design of voltage monitoring, BMW (Preh) using LT6801,A123 hardware compare IC8, once MCU failure when an exception or communication can trigger the alarm directly on the hardware. Compared to Tesla design easier. Especially using UART communication rather than the CAN, more like IT’s solution.

| Single battery Cell

Available from Panasonic on the Spec at 0.5C full/1C (100%DOD) 500cycle capacity under conditions of reduced when BOL 68%, attenuation is more serious.

Also 1C/1C charge-discharge experiments of 150cycle, I3 and on comparison of Model s battery.

Several life cycle data were well above explains why the Model s’s breakthrough in the passenger car into the 85kwh such a great battery. Because Panasonic 18650 battery cycle life in a 1C ratio is poor. So by high capacity must be to reduce the rate under the same conditions, ensure a long cycle life; and large-capacity battery ensures that the vehicle in full life-cycle cycle few times enough. By 20KWH of energy consumption per hundred kilometers, 200,000 km for 85KWH PACK, but only 470cycle.

As more custom battery battery car field standardization and mass, 18650 batteries with a low-cost advantages and high conformance would quickly disappear, even if Tesla had hoped that through the draw of the open patent technology line up, but were not successful. Open patent stunts and publicity than practical.

However, in the age of the electric vehicle supply chain is not yet mature, Tesla is with excellent technical choice of integrated thinking in a variety of non-automotive grade “gather together”, a product of epoch-making significance.

So to say that Tesla battery power than traditional car companies do well, Tesla to work instead to do something they can’t do. Traditional car companies improve supply chain system, long-term accumulation of standard, large market share a few promoting electric cars has become a burden on this matter.

Tesla can afford to give up the automotive supply chain in the industrial product selection, Autosar, ISO26262 put aside for the time being, can worry just like traditional car about electric vehicle technology gone too radical, causes a fire, runaway accidents and impact sales of traditional cars. But then Tesla and traditional car companies competitive advantage continues to be set under the historical conditions of the solution? I think it’s not.

What does Tesla’s core competencies should be? Battery management software algorithm.

| Tesla’s core strengths is that basic technology

Personally think that battery technology is not Tesla’s core strengths, but basic technologies. As in 1983 Apple Lisa launched PC core technology is never to use the mouse, 2001 iPod core technology lies not in a 1.8-inch hard drive. Hello Kitty iPad Cases

2014 the first dismantling of Tesla when the privilege of participating in the Model s, is mainly responsible for the ESS was part of the Benchmark. Have to say that when the project is completed, to Tesla’s mystique and legend faded a lot. As American troops seized the first MiG 25 fighter, too excited to find its strong performance, the result was not found in the underlying technologies are obviously disruptive breakthrough. Can said Tesla single on each items details technology, is not superior, even some part of design slightly explicit hasty (like ESS system of low integrated of caused manufacturing process and late maintenance of difficulty, and more non-car level parts and the programme application brings of risk,), but will all in engineers eye in the does not perfect of child parts integrated in with zhihou, still ready has a paragraph stunning of products.

Tesla’s achievements more accurately in the product definition rather than the core advantages of the technology. Why both with major vehicle manufacturing capabilities and a lithium-ion battery technology in Japan does not appear high performance electric vehicle?

Because at the time (as is now the case) they don’t think the product is safe enough, the price is acceptable. Why even have proof of Tesla’s market value, Germany auto enterprises still take in electric propulsion, because, with their technical standards to a Tesla product, whether it is a design or manufacturing process do not mature at all. As a new car company and does not possess the knowhow accumulated may hit predecessors had known for a long time should avoid reefs, but at the same time is also possible because removing the burden of restrictions and the first to discover a new continent.

Current automotive industry has an increasing number of new entrants to join, can change over the past 10 years the mobile phone industry as a reference during the decline of Nokia, Apple, Google’s rise is not just the strength of competition, more communication industry and computer software industry competition for mobile phone property. If the mobile phone or communication technology to promote products that Apple and Google are not necessarily Nokia’s rivals, as mobile phones become the computer and software industries to promote products, writing App for Nokia, mobile full interoperability with the PC supply chain is not an order of magnitude compared with Apple, Google, nature and how to win it.

Same way we think about the future of property of the car what would it be? Control performance of transport, still manned intelligence robot? This property determines whether the definition of traditional companies in the next production is still in the sale, manufacture, supply chain, or in artificial intelligence, cloud computing technologies as its core business of high-tech companies in the future supply chain structure accounted for a larger proportion.

Tesla in the field of battery technology compared to traditional companies, instead of advantage in the future could be a disadvantage. Instead, unmanned is the life-saving straw.

| Written on the back

Once from the engineer’s point of view, can often expose the enterprise to create the perfect. After all, the product design process is a process of compromise and trade-off, which often try to use in product marketing “uncompromising” and “not on” such concepts (such as some phone companies in the country), and contrary to the nature of the design.

But when you are a consumer, when Tesla still has a very strong appeal to me. The attraction is not the source of the use of advanced or backward technologies, but above the technology stack, and the performance parameters of the product quality, the temperament is one of many people who want to feel from the other models cannot be, I think this is where Tesla’s most successful.

Lei Feng network Note: published by the author in this paper Lei feng’s network (search for “Lei feng’s network” public concerns), please contact the authorized and keep the source and author, no deletion of content.

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Originally published at on August 30, 2016.

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