Describe Tesla Model 3 battery technology

Model3 musk announced last year on the battery pack used when we know, Tesla use ratio of the company's latest battery technology, eliminated Panasonic battery 18650, and use 21700 battery, by the "super battery factory", of Iowa (Giga factory) production.

With cylindrical lithium battery, 21700 of the specifications of the battery to 21 mm in diameter, 70 mm in length, type than the theoretical limit of 18650 (18 mm in diameter, length, 65 mm) is more advantageous.Therefore, 21700 lithium battery was the first to be used in the Model3.

1.21700 the advantage of the battery

From the edge, 21700 relative to 18650 mainly in the energy density, cost, lightweight three aspects has carried on the improvement of ascension, the three points into action (ascension that Model3 sounds more "SAO" gas, we bit by bit to analyze:

1) the energy density increases more than 20%

Battery energy density is better than 2170018650 battery.From the Tesla disclosure of information in the existing conditions, the production of 21700 battery energy density in 300 wh/kg, than the original 18650 battery system 250 wh/kg increase about 20%.From Panasonic power lithium battery monomer of test data, the volume of its 21700 battery energy density is much higher than 18650 type battery monomer.The ascension to monomer batteries energy density is much higher than the margin of 20% after the group ascension.

2) battery system costs fell by about 9%

Lithium battery price information published by the TV university data according to Tesla, expect the 21700 power lithium battery system at a price of $170 per KWh, compared to 18650 for $185 / KWh, price drop of about 8.1%.System costs about $18650 and $171 per KWh, switch to 21700, after the system costs about can achieve about 9% decline, 155 $/ KWh.

After monomer capacity improvement, PACK with the number of required parts to reduce drive PACK costs down.Switch from 18650 to 21700, after the battery monomer battery capacity can reach 3 ~ 4.8 Ah, soared 35%, under the same energy can decrease the number of batteries required about one-third, series-parallel Tesla Models electric vehicles use 7104 section 18650 battery to battery pack, on the new Models3, use after 21700, the battery section number will drastically reduced.While decrease the difficulty of system management reduces with the proportion of the battery Pack use the accessories such as metal structure and electrical fittings number, Tesla Pack cost about 24% of total system cost, cost of battery Pack is expected to decline in more substantial.

It is worth mentioning that Tesla did not Model3 battery design for easy change pattern, Tesla thoroughly seems to be to abandon the switching scheme, which is closely related to cost.

3) lightweight reduced by 10%

The new 21700 batteries, after system compared with the current battery can reduce 10% of the components and the weight, so as to further reduce the weight of the battery Pack, the vehicle energy density will be part of ascension.

Model3 a total of four configuration, respectively is: 50, 65, 80, P80D, corresponding Numbers is to load the total capacity of the battery.Battery capacity corresponding to different range (EPA) : 357 km, 454 km, 550 km and 539 km.But just curb weight, respectively is 1650 kg, 1725 kg, 1800 kg, 1925 kg.As a whole size (1443 mm) / 4694/1849 with BMW 3 series (1540 kg to 1650 kg) of vehicles, were much heavier.

In addition, Tesla also increased some other clever design to save weight and cost.For example, it removed the outer pack heaters, and using only the quantity of heat of automotive powertrain, even if the car stopped, also for battery heating.This is because the battery needs to be in a suitable temperature, in order to keep its best performance, which means that they need to cool overheated environment, under heating in cold weather.

2.21700 the battery "black box"

The so-called "black box" refers to from the user's point of view of a device or product, don't care about its internal structure and the principle, and only care about its function and how to use these functions.Then we will to find out the condition of the 21700 from the user's point of view!

1) whether to accept the downstream market change?

What type of battery production, battery enterprises should be affected by many factors.The emphasis of the new energy car research and development of "positive", request, from the perspective of the function design, it also determines the must, from the perspective of the use to push the battery type and specification, therefore, whether the battery model change is mainly to see the downstream market.

The suitability of "18650 is very strong, in addition to the electric car, also can be in 3 c digital digest, unmanned aerial vehicles, electric tools, and other field.But for 21700, have not formed the industrial chain of effective to digest these batteries, this will undoubtedly increase the cost."

2) equipment and processes meet?

21700 battery production equipment, production process and so on, not once a day can be ready, how to layout also look at the battery production enterprise competition strategy.

The battery cost reduction is based on yield and yield.Starting point for research (SPIR), according to data from the 18650 battery Panasonic, Samsung SDI rate generally over 98%, the domestic product rate of more than 95% in the general, but it still means that there are more B product batteries need to be processed, it is a severe challenge for 21700.

3) the policy support?

In addition to the market demand is not obvious and battery enterprise manufacturing technology, the national policy on cell size standard choice of domestic battery size is also significant impact.

Formulated by ministry of electric vehicles with power battery products size "in the draft, cylindrical battery model recommended by only two 18650 and 32650, once the compulsory unity would be adverse to the other types of batteries.If not explicitly support battery size standards promulgated by the state, the development prospects of this kind of model will not as good as it seems.

3. The capacity of battery pack

Unlike previous ModelS and ModelX, Tesla in release Model3 without regular "KWH" are used to indicate the battery capacity, but gives a charging rate: in the case of a 240 v, 30, charge can travel 30 miles per hour (48.28 kilometers).

Tesla's battery pack

So, Model3 how big is the battery capacity?According to the EPA official authentication information, standard edition Model3 range of 350 kilometers, 50 KWH battery capacity, using 2976 section 21700 batteries, each section 31 battery constitute a brick.The battery and brick is divided into four modules, including 2 group contains 23 brick of battery module, 2 group contains 25 battery module of the brick.

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Tesla battery pack layout diagram

Model3 mileage range can reach 500 kilometers long, the battery capacity is 80.5 kWh, using 4416 section 21700 batteries, each section 46 battery constitute a brick.And the standard version Model3, these batteries brick is divided into four modules.

4. Battery attenuation

For any rechargeable battery, attenuation is inevitable.With the increase of charging cycles, the battery is the cathode reaction material yield loss, electrolyte performance will decline, in the actual capacity of the battery.In general, the chemical properties of active lithium battery, for example, in 500 after charging cycles, the attenuation of power will be around 80%.

For the ModelS/X, Tesla never did promise on the battery health.But Model3 but an official data, which is 200000 km, still can be maintained at more than 70% of capacity.But the truth is Tesla's officer xuan so ideal?

According to foreign media reports, according to a hundreds of Tesla, according to the survey data of the real owner after traveling 100000 kilometers, ModelS/X battery capacity fell by 5%, after 300000 km, the majority of the Tesla also can guarantee more than 90% of the battery capacity, after 800000 kilometers, can still remain above 80% level.And frequent charging and discharging, it can even slow attenuation.

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