EV BATTERY

In order to win over consumers, a battery pack must be competitive with gasoline-powered motors. This is a significant barrier because internal combustion engines (ICEs) do not have the intricate problems that electric batteries must solve.

The following are some typical problems that can impair the operation of a battery pack:

Batteries cannot operate at full capacity in cold weather. The ideal operating temperature for batteries is between 68°F and 77°F (20°C and 25°C). It's crucial to keep things at the proper working temperature.

Over time, natural wear causes batteries to lose some of their available power. The driving experience must not be impacted by this power loss, according to EV manufacturers.

For best performance, battery cells must be balanced, which calls for a constant voltage across the board. During charges, battery cells are rebalanced, but as they get older, they become less capable of doing so. Additionally, the popularity of quick charges is posing a threat to the performance of balancing.

Let's review the following topics in order to gain a better understanding of the intricacy of battery technology:

1.       A battery pack is what?

In order to power an electrical system, such as an energy storage system or an electric vehicle (EV), a battery pack is a device that stores electrical energy (ESS). The battery pack has cells that are all interconnected and used to store energy.

Battery packs need a minimum voltage level that a single cell cannot reach in order to provide adequate power. As a result, several cells are linked together in series to increase voltage. Small-capacity cells are used in some designs. Cells are linked in parallel to increase capacity and produce the needed battery energy. Parallel cell connections provide power as if they were one huge cell.

Battery packs are constructed from numerous, smaller components known as battery modules (or sub packs). These modules have fewer cells that are linked in series and parallel. They are typically handled safely because they are at a lower voltage. When only a few cells need to be replaced and they can be done so without having to replace the complete battery, modules make service easier. EV batteries are typically constructed from four to forty modules connected in series.

2.       Batteries and Their Parts

In an electric car, the battery pack is the most expensive component. It is a sophisticated system with numerous intricate parts. Some of the key elements are listed below.

·         The crucial elements of a battery pack are its cells. The cell's chemistry refers to the materials that make up the cell. The performances and requirements that can be achieved by various battery chemistries vary. Cells can be divided into two categories: power cells and energy cells. Various alternatives exist that, depending on the application, can offer the ideal trade-off. The most popular chemical in the EV sector is the lithium-ion cell (li-ion cell). Alternative chemistries, such as Nickel-Metal Hydride (NiMH), are occasionally utilised because they have a slightly better lifetime.

·         Cells and collections of cells are connected in series or parallel via electrical connectors like bus bars, wires, or other distribution conductors. Typically, laser welding or ultrasonic bonding are used to make these connections. Fasteners can be used to mechanically connect bus bars between modules.

·         To mechanically attach battery components together while enhancing the thermal characteristics between surfaces, thermal interface materials (TIMs) such pastes, adhesives, and gap fillers are injected between them. TIMs are turning into crucial components with the development of the structural battery pack.

·         Cells are safeguarded by the Battery Management System (BMS), which keeps an eye on vital indicators like voltages, currents, and temperatures. It interacts with several systems, including temperature control and engine management, and is in charge of cell balancing (to keep the cells operating at their best at the appropriate voltage). It also has safety features that, if necessary, may turn the battery off.

·         The battery's thermal needs are met and the battery's cells are protected by the Battery Thermal Management System (BTMS), which regulates the thermal energy in the electric car's interior and drivetrain. A heat exchanger, tubes, hoses, cold plates, pumps, valves, and temperature sensors are just a few of the parts that make up the BTMS.

·         The battery management system is in charge of the switch known as the contactor system. It has the ability to interrupt the flow of current to the traction motor and other high-voltage components from the main battery to the high voltage bus.

·         The Housing is a strong shell that shields the battery from elements including salt, dust, and water. It aids in preserving the battery's precise temperature and electrical insulation and guards against rust and sluggish shorts.

·         The Communications System makes sure that the electric vehicle's various parts can communicate with one another. The CAN bus protocol is the most popular.

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The 4 Major Battery Pack Design Types

a.       Accessories 12V Battery Packs

Low energy applications like headlights, radio systems, and other accessories employ 12V batteries because of their low voltage. They are used to kick start the engines in gasoline and hybrid vehicles. They are utilised in electric vehicles as a backup energy source for the primary electric battery (traction battery). For instance, it is utilised to turn on the traction batteries and power some essential parts when the electricity has been turned off for safety.

Lead-acid batteries are the most popular form of 12V batteries that were historically produced using the lead-acid cell chemistry. There could only be six cells in each of these packets. The most contemporary 12V batteries are lithium-ion battery packs, which are lighter and perform better thanks to their lithium cells.

Small and frequently found under the hood, 12V batteries are. In an effort to increase safety, automakers started putting them inside the trunk more lately because doing so reduces the possibility of short circuits during collisions. Since frontal collisions are more common, the battery is better shielded from blows when it is placed at the back.

b.      Packs of hybrid batteries

Batteries for hybrid vehicles are much smaller and have less energy than EV batteries. But hybrid batteries of today often offer a range of 30 to 50 miles (50 and 80 km). They eliminate the need for the internal combustion engine for the majority of short-distance trips (ICE). Comparing that to the original versions, which provided just 0.6 miles of autonomy, is a significant increase (1 km).

While the combustion engine is least effective, like when accelerating, hybrid battery packs are designed to complement it. The aim is to reduce gasoline use as much as feasible. The battery can also replenish itself by recapturing energy lost during braking (regen braking).

c.       Battery Packs for EVs

EV batteries are full-sized batteries designed to power the entire range of the vehicle, including the traction motor and accessories, in contrast to other battery pack designs. Compared to other types of batteries, EV batteries currently available may consume between 90% and 95% of their available energy, which is between 20 and 130 kWh. With a range of 485 miles, the Mercedes EQS is the electric vehicle with the longest driving range (780 km).

A sizable amount of the vehicle's weight and volume is made up of EV batteries. They can be up to 450 kg (1000 LBS) in weight, which is one-fourth of the weight of the entire car. There are many high voltage designs available, ranging from 400V to 900V. The most modern designs include them into the framework of the vehicle.

d.      Battery Packs with High Performance

Batteries made for Formula E races are high performance battery packs. They are split into two groups: hybrid and all-electric vehicles. They have a very light structure because they are built of composite materials. Some high-performance batteries can be changed during racing because they are detachable.

These batteries, despite their diminutive size, can produce extremely high power. More specifically, they have the capacity to output several hundred kW of power, which is sufficient to power an entire neighbourhood. They have an excessive cooling system because of the high power requirement.

Energy efficiency is higher for high-performance battery packs than for other battery kinds. For instance, they can recover more of the energy lost during braking (regen braking).

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 Designs for Battery Packs Have Evolved

Battery pack designs have significantly changed over the past ten years in response to consumer demand for longer battery life. In order to further improve quality and reduce costs, production may now be streamlined using more sophisticated manufacturing techniques like lasers thanks to the rising interest in EVs.

Extra information about EV battery

A battery electric vehicle (BEV) or hybrid electric vehicle's electric motors are powered by a rechargeable battery known as an electric vehicle battery (EVB, often referred to as a traction battery) (HEV). They are made especially for high electric charge (or energy) capacity lithium-ion batteries.

A rechargeable battery known as an electric vehicle battery (EVB, often referred to as a traction battery) powers the electric motors in a battery electric vehicle (BEV) or hybrid electric vehicle (HEV). They are specifically designed for lithium-ion batteries with high electric charge (or energy) capacities.

Due to their high energy density in relation to their weight, lithium-ion and lithium polymer batteries are the most popular battery types in contemporary electric vehicles. Lead-acid ("flooded", "deep-cycle," and "valve-regulated lead acid"), nickel-cadmium, nickel-metal hydride, and, less frequently, zinc-air and sodium nickel chloride ("zebra") batteries are other types of rechargeable batteries used in electric vehicles. [1] Batteries' electrical capacity, or "electric charge," is measured in ampere hours or coulombs, with the total energy being expressed in kilowatt-hours (kWh).

Lithium-ion battery technology has advanced since the late 1990s as a result of demands from portable devices, laptop computers, mobile phones, and power tools. These improvements in performance and energy density have benefited the BEV and HEV market. Lithium-ion batteries, in contrast to prior battery chemistries like nickel-cadmium, allow for daily discharge and recharge at any level of charge.

A BEV or HEV's battery pack accounts for a sizeable portion of the cost. Since 2010, the price of electric vehicle batteries has decreased 87% per kilowatt-hour as of December 2019. [2] As of 2018, vehicles like the Tesla Model S that have an all-electric range of more than 250 miles (400 km) are commercially available in a wide range of vehicle segments. 

Because BEVs are more energy efficient, their running costs are lower than those of comparable internal combustion engines because they use less power.

Battery types for electric vehicles

1.       Lead-acid

The most traditional, affordable, and historically prevalent type of automotive battery is the flooded lead-acid battery. Deep cycle batteries and automotive engine starter batteries are the two primary categories of lead-acid batteries. In contrast to deep cycle batteries, which are intended to supply continuous electricity to power electric vehicles like forklifts and golf carts, automobile engine starter batteries are made to utilise a tiny portion of their capacity to offer high charge rates to start the engine. Recreational vehicles also employ deep cycle batteries as auxiliary batteries, but these batteries require a distinct, multi-stage charging process. Lead acid batteries shouldn't be depleted below 50% of their capacity because doing so reduces their lifespan.

Flooded batteries need to have their electrolyte levels checked and occasionally have the water that gasifies during a charging cycle replaced.

Due to their established technology, wide availability, and low cost, lead-acid batteries were formerly used by the majority of electric cars, with the notable exception of some early BEVs, such as the Detroit Electric, which utilised a nickel-iron battery. Deep-cycle lead batteries are pricey and often need to be replaced every three years, lasting less than the car itself.

In EV applications, lead-acid batteries make up a sizeable (25–50%) share of the overall vehicle mass. They have substantially less specific energy than fossil fuels, like all batteries—in this case, 30–50 Wh/kg. Even the finest batteries tend to result in larger masses when used in vehicles with a standard range, despite the fact that the difference isn't as stark as it initially seems due to the lighter drive-train in an EV. With decreasing temperatures, the present generation of common deep cycle lead acid batteries' efficiency (70–75%) and storage capacity drop, and when power is diverted to drive a heating coil, efficiency and range are reduced by up to 40%.

Lead-acid batteries account for a sizable portion (25–50%) of the total vehicle mass in EV applications. Like other batteries, they have a far lower specific energy than fossil fuels—in this case, 30–50 WH/kg. Although the difference isn't as pronounced as it initially seems because an EV's drive-train is lighter, even the best batteries tend to result in greater masses when utilised in vehicles with a typical range. The efficiency (70–75%) and storage capacity of the current generation of common deep cycle lead acid batteries decrease with lowering temperatures, while efficiency and range are lowered by up to 40% when power is diverted to drive a heating coil.

2.       Metal hydrides of nickel

Batteries made on nickel-metal hydride are today regarded as a relatively established technology. They have a specific energy of 30-80 Wh/kg, which is far higher than lead-acid despite being less efficient (60-70%) in charging and discharging than even lead-acid. As seen by their employment in hybrid vehicles and the surviving first-generation NiMH Toyota RAV4 EVs that are still in good operating condition after 100,000 miles (160,000 km) and more than ten years of use, nickel-metal hydride batteries can have extraordinarily long lives when used appropriately. The low efficiency, excessive self-discharge, extremely picky charge cycles, and subpar performance in cold conditions are drawbacks.

The second generation EV-1's NiMH battery was made by GM Ovonic, while Cobasys also produces a virtually identical battery (ten 1.2 V 85 A/h NiMH cells in series as opposed to eleven cells for Ovonic battery). This performed admirably in the EV-1.  In recent years, the use of these batteries has been constrained by patent encumbrance.

3.       Zebra

The electrolyte for the sodium nickel chloride, or "Zebra," battery is molten sodium chloro aluminate (NaAlCl4) salt. The Zebra battery has a specific energy of 120 Wh/kg and is a relatively established technology. Cold weather does not significantly influence the operation of the battery because it must be heated in order to be used, with the exception of rising heating costs. Zebra batteries may survive for a few thousand charge cycles and are nontoxic. They have been utilised in a number of EVs, including the Modec commercial vehicle. The Zebra battery has some drawbacks, such as a low specific power of only around 300 W/kg and the need to heat the electrolyte to about 270 °C (518 °F), which consumes some energy, makes it difficult to store charge for an extended period of time, and may even be dangerous.

4.       Lithium-ion

In the beginning, lithium-ion batteries (and the mechanistically equivalent lithium polymer batteries) were created and marketed for use in laptops and consumer gadgets. They have emerged as the primary battery type for usage in EVs due to their high energy density and long cycle life. A lithium cobalt oxide cathode and a graphite anode were the first commercially available lithium-ion chemistry, as first demonstrated by N. God shall in 1979, followed soon after by John Good enough and Akira Yoshino. The drawbacks of conventional lithium-ion batteries include age-related performance degradation, susceptibility to temperature, and low temperature power performance. Traditional lithium-ion batteries present a fire safety hazard if pierced or charged incorrectly due to the flammability of organic electrolytes, the presence of highly oxidised metal oxides, and the thermal instability of the anode SEI layer.  In some climates, heaters may be required to warm these early cells because they could not take or deliver charge when very cold. This technology has a modest level of maturity. A modified version of conventional lithium-ion "laptop battery" cells were used in the Tesla Roadster (2008) and other vehicles made by the firm. Recent EVs use novel lithium-ion chemistry modifications that give up some specific energy and specific power in exchange for fire resistance, environmental friendliness, rapid charging (in as little as a few minutes), and longer lifespans. These variations (phosphates, titanates, spinels, etc.) have been shown to have a much longer lifespan, with lithium iron phosphate batteries used in A123 types lasting at least more than 10 years and more than 7000 charge/discharge cycles, and LG Chem anticipating their lithium-manganese spinel batteries to last up to 40 years. In the lab, there is a lot of work being done on lithium-ion batteries. The Subaru prototype G4e already contains lithium vanadium oxide, which doubles energy density. [Reference needed] In the anode, silicon nanowires, silicon nanoparticles, tin nanoparticles, tin nanoparticles, composite and superlattice cathodes, among others, offer several times the energy density [clarification needed]. According to recent research, Li-ion batteries are more susceptible to deterioration from heat exposure and quick charging than from ageing and actual use. The average electric vehicle battery will still have 90% of its initial capacity after six years and six months of operation. For instance, because the battery in a Nissan Leaf lacks an active cooling mechanism, it will deteriorate twice as quickly as the battery in a Tesla.