Electric vehicles are powered by the chemical energy that is stored in the rechargeable battery packs. These electric vehicle batteries are specially designed for high ampere-hour or kilowatt-hour capacity. Furthermore, the electric vehicle battery provides a reversible chemical reaction during both the charging and discharging process. When the electric vehicle battery is discharging, the electric current flow from the cathode (+ve plate) to the anode (-ve plate) and vice-versa during charging of the battery.
However, there are many types of electric vehicle batteries available in the market and so, you can use the most suitable battery type for your application requirement. The different types of rechargeable electric vehicle batteries are lead-acid batteries, NiCd (nickel-cadmium) batteries, NiMH (nickel-metal hydride) batteries, and lithium-ion batteries. Among these, nickel-cadmium (NiCd) batteries are less prone to damage, last longer, and robust; but they are recognized as the oldest technology and are highly toxic. Furthermore, NiCd batteries are replaced by the other technology batteries i.e. Li-ion and NiMH that are environment-friendly and highly efficient. Now, let’s dig into detail about each type of electric vehicle batteries.
Lead-acid batteries: –
Lead-acid batteries are considered to be reliable and highly toxic, but an outdated technology commonly available in the market at very cheaper prices. Furthermore, these lead-acid batteries are available in two types, they are – automobile engine starter batteries used to start the engine and deep cycle batteries used to provide continuous electricity to run electric vehicles. In addition, lead-acid batteries require regular inspection of an electrolyte level, occasional replacement of water, and has a shorter lifespan which typically needs replacement every 3 years.
Also, these lead-acid batteries have a negative impact on the environment as they are highly toxic, contain concentrated sulfuric acid, and release harmful gases. Do not allow a lead-acid battery to discharge below 50% of its capacity as it reduces the battery’s lifespan. They have poor specific energy rate (34 Wh/kg) and represent 25-50% of the vehicle’s total mass. Furthermore, this battery type was used by the previous electric vehicles but not by the new EV designs due to major disadvantages. However, new developments are being made in the other battery types.
Nickel metal hydride (NiMH) batteries: –
Nickel metal hydride (NiMH) for electric vehicle batteries are being developed with mature technology. These NiMH batteries are considered to be the superior ones compared to the lead-acid batteries as the specific energy of NiMH batteries have double the value of 68 Wh/kg (with a range of 60 to 120 Wh/kg). Thus, Nickel-metal hydride batteries have lower battery weight and require less space for storing. However, the specific energy of NiMH batteries is lower as compared to the Li-ion batteries as their specific energy value is 40% higher. However, most of the electric vehicles with NiMH batteries have been successfully operating on roads for almost 7 years and are well-proven in the market. Furthermore, NiMH batteries for electric vehicles are highly durable.
In addition, some of the advantages of Nickel Metal Hydride (NiMH) batteries include: they are recyclable and contain little toxic material. However, for every product, there are disadvantages along with advantages, some of the disadvantages of NiMH batteries include self-discharge (up to 12.5% per day at room temperature with decreasing performance at a higher temperature), low charging efficiency, and high heat generation during charging and discharging. Thus, NiMH batteries require a cooling system that significantly increases the cost of the battery, weight and therefore, limits the no. of batteries that can be used. Furthermore, a number of legal disputes have shifted their focus to Li-ion technology and limited the use of NiMH batteries in electric vehicles.
Lithium-ion Batteries: –
Nowadays, Lithium-ion batteries are most commonly used in electric vehicles. Furthermore, the cathode of the lithium-ion battery is made with lithium cobalt oxide and anode with graphite. According to the Financial Times, it is believed that by 2025, Li-ion batteries will take up to 90% share of the electric vehicle batteries. These Lithium-ion technology batteries are being developed in order to overcome the shortcomings of other technology batteries. In addition, Li-ion batteries have an amazing specific energy rate of 140+ Wh/kg which is their major advantage. However, some of the advantages of Lithium-ion batteries are good charge cycle rate (capable of being recharged no. of times), lightweight, better self-discharge rate, higher cell voltage, and higher energy density.
Furthermore, these batteries are light in weight and deliver greater performance, but high-price is their biggest advantage. The production cost for Li-ion batteries is 40% higher than nickel batteries, but the research on Li-ion technology battery helped in the decrease in production costs. However, if the battery is overcharging and thermal runaway causes electric vehicles to catch fire, safety remains a major concern with lithium-ion batteries. In addition to this, if the battery charging is fluctuating, then it can be dangerous. Thus, an advanced battery management system (BMS) is necessary that helps in monitoring each cell’s temperature and voltage, the state of health (SoH), and the state of charge (SoC). Therefore, advanced BMS enables safe and reliable operation, optimized electric vehicle performance, and balanced cells for longer battery life.