question: Why do electric car manufacturers use lots of batteries wired together instead of one big one?
comment: Well one cell is a fixed voltage, about 3.7V for Lithium, and I have a PHEV car with a 120kW motor. If it ran at 3.7V the wires to the battery would need to handle 33kA. My math shows you'd need about 90 strands of 0000 guage (half inch diameter) wires to the battery, one positive and one negative. This cable would be about 4.5-5 inches in diameter of solid metal, very heavy and very expensive. Plus the battery would be one single part, and it needs to be made perfectly in the factory every time. One mistake and it's a broken battery. Second, all the electronics need similarly sized wires, that makes the electronics huge. Instead, they make them out of smaller cells and connect them together, typically to get 300-500V. These voltages need no more than standard insulation, and the wires are easily 100 times smaller. Plus since the battery is made out of many identical cells, the factory can build lots of little pieces, optimize their equipment for the small batteries, and if one is a dud, they can throw out the cheap tiny battery and continue on before building the car. The other issue is cooling, big car batteries need a lot of cooling to cool them, typically cannot have more than an inch from the nearest coolant line. A giant single cell would need a way to run coolant through the cell, where multi-cell packs can run coolant between the cells. This is much easier to design.
passages: Lithium-ion cells in pouch format are being investigated to power battery electric vehicles. While it is possible to use a large number of cells of small capacity to obtain required levels of power and energy to drive a vehicle, some manufacturers and research centres are looking into large-format lithium-ion cells of capacities exceeding 50 Ah for this purpose. With higher energy content per cell, the number of cells and electrical connections in a battery pack would certainly decrease but the danger associated with individual cells of such high capacity might be greater.
   Modern SLI batteries are lead-acid type, using six series-connected cells to provide a nominal 12 volt system (in most passenger vehicles and light trucks), or twelve cells for a 24 volt system in heavy trucks or earth-moving equipment, for example.
  
  Section::::Battery in modern cars.:Electric cars.
  
  Battery electric vehicles are powered by a high-voltage electric vehicle battery, but they usually have an automotive battery as well, so that they can use standard automotive accessories which are designed to run on 12 V.
  
  Section::::History.
   BULLET::::3. The space created facilitates the storage of the batteries, allowing for extra modules to be fitted which would offer increased power and range compared to previous electric vehicles.
  
  Section::::Vehicles.
  
  Section::::Vehicles.:Mitsubishi Colt EV (2005).
  
  Based on the platform of a Mitsubishi Colt, and first exhibited in 2005, it was the first Mitsubishi EV where mass production and public sales were mooted, with a suggested price tag of US$19,000.
   Section::::Battery swapping charging method.:Applications.
  
  If the electrical changing station mode is successful in the future, there is one significant problem how can the car industry ensure each individual is using the same brand of car, the battery size between different brands cannot be unified. Therefore how many changing station is needed for serve the hundreds and thousands of brands of electrical car in the city.
   Many modern motorcycles and All-terrain vehicles (ATVs) on the market use AGM batteries to reduce likelihood of acid spilling during cornering, vibration, or after accidents, and for packaging reasons. The lighter, smaller battery can be installed at an odd angle if needed for the design of the motorcycle. 
   Electric-vehicle batteries differ from starting, lighting, and ignition (SLI) batteries because they are designed to give power over sustained periods of time. Deep-cycle batteries are used instead of SLI batteries for these applications. Traction batteries must be designed with a high ampere-hour capacity. Batteries for electric vehicles are characterized by their relatively high power-to-weight ratio, specific energy and energy density; smaller, lighter batteries reduce the weight of the vehicle and improve its performance. Compared to liquid fuels, most current battery technologies have much lower specific energy, and this often impacts the maximal all-electric range of the vehicles. However, metal-air batteries have high specific energy because the cathode is provided by the surrounding oxygen in the air. Rechargeable batteries used in electric vehicles include lead–acid ("flooded", deep-cycle, and VRLA), NiCd, nickel–metal hydride, lithium-ion, Li-ion polymer, and, less commonly, zinc–air and molten-salt batteries. The most common battery type in modern electric cars are lithium-ion and Lithium polymer battery, because of their high energy density compared to their weight. The amount of electricity (i.e. electric charge) stored in batteries is measured in ampere hours or in coulombs, with the total energy often measured in watt hours.
   For a person interested in sports car performance and appearance, the creation of a satisfying conversion will likely lead to a number of difficulties in such details as battery disposition, as such vehicles generally have available space distributed in small volumes around the vehicle. This leads to complexity in securing and wiring batteries. These vehicles can offer stunning performance in the lower speed ranges owing to light weight and rear wheel drive, and may also offer good range due to their superior aerodynamics.
   Section::::Specifications.
  
  As production began in 2017, the base Model 3 was announced to have a 50-kWh battery with a range of about while the optional 75-kWh battery would have a range of about . In the event, Tesla did not produce any base Model 3s in 2017 or 2018. The battery uses 2170-size lithium-ion cells
   Battery pack designs for Electric Vehicles (EVs) are complex and vary widely by manufacturer and specific application. However, they all incorporate a combination of several simple mechanical and electrical component systems which perform the basic required functions of the pack.
  
  The actual battery cells can have different chemistry, physical shapes, and sizes as preferred by various pack manufacturers. Battery pack will always incorporate many
  
  discrete cells connected in series and parallel to achieve the total voltage and current requirements of the pack. Battery packs for all electric drive EVs can contain several hundred individual cells.
   Electric double-layer capacitors (or "ultracapacitors") are used in some electric vehicles, such as AFS Trinity's concept prototype, to store rapidly available energy with their high specific power, in order to keep batteries within safe resistive heating limits and extend battery life.
  
  Since commercially available ultracapacitors have a low specific energy no production electric cars use ultracapacitors exclusively. But using an Electric car with both Battery and ultracapacitor can reduce the limitations of both.
  
  Section::::Promotion.
   Another vehicle that takes up a prominent place in Micro-Vett range is the Daily in bimodal version, manufactured since 2004. By placing an electric motor on the shaft, the vehicle can be driven both by diesel engine both by electric motor, ensuring a unique flexibility of use. Battery recharge occurs both from electrical grid both when the vehicle is driven by the diesel engine. This project is shown to Iveco which, however, is not interested in. So Micro-Vett directly markets this vehicle with a sales volume from 2004 to 2011 of approximately 600 units.
  
  Section::::History.:Lithium batteries and FIAT range.
   BULLET::::- Audi Q7 e-tron: 17 kWh
  
  BULLET::::- BMW i8: 7 kWh
  
  BULLET::::- BMW 2 Series Active Tourer 225xe: 6.0 kWh
  
  BULLET::::- BMW 330e iPerformance: 7.6 kWh
  
  BULLET::::- BMW 530e iPerformance: 9.2 kWh
  
  BULLET::::- BMW X5 xDrive40e: 9.0 kWh
  
  BULLET::::- Chevrolet Volt: 16–18 kWh
  
  BULLET::::- Chrysler Pacifica Hybrid: 16 kWh
  
  BULLET::::- Ford Fusion II / Ford C-Max II Energi: 7.6 kWh
  
  BULLET::::- Fisker Karma: 20 kWh
  
  BULLET::::- Honda Accord PHEV (2013): 6.7 kWh
  
  BULLET::::- Honda Clarity PHEV (2018): 17 kWh
  
  BULLET::::- Hyundai Ioniq Plug-in: 8.9 kWh
  
  BULLET::::- Kia Niro Plug-in: 8.9 kWh
  
  BULLET::::- Koenigsegg Regera: 4.5 kWh
  
  BULLET::::- Mini Countryman Cooper S E: 7.6 kWh
   Coordinating generation units is a difficult task for a number of reasons:
  
  BULLET::::- the number of units can be large (hundreds or thousands);
  
  BULLET::::- there are several types of units, with significantly different energy production costs and constraints about how power can be produced;
   Lithium-based batteries are often used for their high power and energy density, although they eventually wear out. Other battery types, such as nickel metal hydride (NiMH), which have a poorer power-to-weight ratio than lithium ion, but are cheaper. Batteries with different chemical compositions are in development such as zinc-air battery which could be much lighter.
  
  Section::::Batteries.:Range.
  
  The range of an electric car depends on the number and type of batteries used, and as with all vehicles, the weight and type of vehicle, performance requirements, and the weather.
   Secondary cells (rechargeable batteries) are in general more economical to use than primary cells. Their initially higher cost and the purchase cost of a charging system can be spread out over many use cycles (between 100 and 1000 cycles); for example, in hand-held power tools, it would be very costly to replace a high-capacity primary battery pack every few hours of use.
   A compact sedan may be a better choice than a subcompact owing to better load capacity and more room for battery placement. Some commercial EV Conversions use vehicles in this size range. One example is a 1992 Honda Civic. In this conversion, the back seat was retained, and there is still enough room to sink nine flooded lead-acid batteries low in the trunk where the spare tire was located, as well as another nine batteries under the hood. Another example is a 1987 Mitsubishi Tredia where the rear batteries have been raised above the trunk floorspace, sealed, and externally vented. With suspension modifications, increasing shock length & spring rating, the car must still be below GVWR, even with the driver and passengers. Exceeding the total design weight of the vehicle would be illegal in some states, and might result in cancellation by an insurance company.
   GM Ovonic produced the NiMH battery used in the second generation EV-1, and Cobasys makes a nearly identical battery (ten 1.2 V 85 Ah NiMH cells in series in contrast with eleven cells for Ovonic battery). This worked very well in the EV-1. Patent encumbrance has limited the use of these batteries in recent years.
  
  Section::::Battery types.:Zebra.
   BULLET::::- Citroen C-Zero / Peugeot iOn (i.MIEV): 16 kWh (2010) / 14,5 kWh (2013-)
  
  BULLET::::- Fiat 500e: 24 kWh
  
  BULLET::::- Ford Focus Electric: 23 kWh (2012), 33.5 kWh (2018)
  
  BULLET::::- Honda Clarity (2018): 25.5 kWh
  
  BULLET::::- Hyundai Kona Electric: 39.2–64 kWh
  
  BULLET::::- Hyundai Ioniq Electric: 28 kWh
  
  BULLET::::- Kia Soul EV: 27 kWh
  
  BULLET::::- Kia Niro EV: 39.2–64 kWh
  
  BULLET::::- Jaguar I-Pace: 90 kWh
  
  BULLET::::- Mini Cooper SE: 32.6 kWh
  
  BULLET::::- Nissan Leaf I: 24–30 kWh
  
  BULLET::::- Nissan Leaf II: 24-60 kWh
  
  BULLET::::- Mercedes-Benz EQ C: 80 kWh
  
  BULLET::::- Mitsubishi i-MIEV: 16 kWh
  
  BULLET::::- Renault Fluence Z.E.: 22 kWh
   Zebra batteries have been used in the Modec commercial vehicle since it entered production in 2006.
  
  Section::::Battery types.:Lithium-ion.
   Common battery
  
  In telecommunication, a common battery is a single electrical power source used to energize more than one circuit, electronic component, equipment, or system. 
   Tesla Motors designed its Model S to allow fast battery swapping. In June 2013, Tesla announced their goal to deploy a battery swapping station in each of its supercharging stations. At a demonstration event Tesla showed that a battery swap operation with the Model S takes just over 90 seconds, about half the time it takes to refill a gasoline-powered car used for comparison purposes during the event. The first stations are planned to be deployed along Interstate 5 in California where, according to Tesla, a large number of Model S sedans make the San Francisco-Los Angeles trip regularly. These will be followed by the Washington, DC to Boston corridor.
   In recent years, Better Place, Tesla, and Mitsubishi Heavy Industries have been involved with integrating battery switch technology with their electric vehicles to extend driving range. In a battery switch station, the driver does not need to get out of the car while the battery is swapped. Battery swap requires an electric car designed for the "easy swap" of batteries. However, electric vehicle manufacturers working on battery switch technology have not standardized on battery access, attachment, dimension, location, or type.
   Most electric vehicles use lithium-ion batteries (Li-Ions or LIBs). Lithium ion batteries have higher energy density, longer life span and higher power density than most other practical batteries. Complicating factors include safety, durability, thermal breakdown and cost. Li-ion batteries should be used within safe temperature and voltage ranges in order to operate safely and efficiently.
  
  Increasing the battery's lifespan decreases effective costs. One technique is to operate a subset of the battery cells at a time and switching these subsets.
   BULLET::::- Tesla Motors
  
  Tesla Motors designed its Model S to allow fast battery swapping. In June 2013, Tesla announced their goal to deploy a battery swapping station in each of its supercharging stations. At a demonstration event Tesla showed that a battery swap operation with the Model S takes just over 90 seconds, about half the time it takes to refill a gasoline-powered car used for comparison purposes during the event.
   In the 1990s a 42V electrical system standard was proposed. It was intended to allow more powerful electrically driven accessories, and lighter automobile wiring harnesses. The availability of higher-efficiency motors, new wiring techniques, and digital controls, and a focus on hybrid vehicle systems that use high-voltage starter/generators have largely eliminated the push for switching the main automotive voltages.
  
  Section::::Design.
  
presuppositions: One big battery would be practical for electric car manufacturers to use. One big battery would be more practical for electric car manufacturers to use instead of lot's of batteries.
corrections: One big battery would be too heavy and expensive for electric car manufacturers to use. One big battery would be too heavy and expensive for electric car manufacturers to use.
raw_presuppositions: One big battery would be practical for electric car manufacturers to use. One big battery would be more practical for electric car manufacturers to use instead of lot's of batteries. One big battery would be practical for electric car manufacturers to use.
raw_corrections: One big battery would be too heavy and expensive for electric car manufacturers to use. One big battery would be too heavy and expensive for electric car manufacturers to use. One big battery would be too heavy and expensive for electric car manufacturers to use.