A Guide to Understanding EV Batteries
In this article, let us roundup all the important information that you need to know about EV batteries. It is our hope that this special guide will help you with understanding EV batteries, how they function, and other components that work together so that your electric vehicle can run.
What is an electric vehicle battery?
Putting it simply, electric vehicle batteries provide the electrical power that makes your EV run. EV batteries are also the heaviest (at an average of 1,000 pounds) and most expensive parts (although prices have dropped significantly in the past few years) of an electric vehicle.
How do EV batteries work?
Electric vehicle batteries have six major components – two electrodes namely the anode or negative electrode and the cathode or positive electrode, electrolyte, separator, current collectors, and casing/housing.
During the DISCHARGE phase of EV batteries, an electrochemical reaction takes wherein ions flow from the anode to the cathode through the electrolyte and separator, releasing electrical energy. Current collectors gather this energy and distribute them to external circuits in the electric vehicle’s various sub-systems.
Meanwhile, the reverse happens during the CHARGING phase. The flow of ions now moves from the cathode to the anode where electrical energy is stored in the electrode and the current collectors for use by the electric vehicle the following day.
As we discussed in a previous article, future EV battery technology hopes to see a reduction in the charging time (which is usually over a period of hours overnight) of EV battery packs.
What is an EV battery made of?
EV battery components mentioned earlier are made from a variety of metals and minerals, which are as follows:
- Anode – Graphite
- Cathode – Lithium, aluminum, nickel, manganese, iron, cobalt
- Separator – Polyolefin, a microporous polymer
- Electrolyte – Lithium hexafluorophosphate
- Current collectors – Aluminum (on the cathode side) and copper (on the anode side)
- Casing – Aluminum, steel
How long does an EV battery last?
To answer the question “How long does an EV battery last?”, based on automotive industry estimates, the current crop of EV battery cells have a projected lifespan of 15 to 20 years, or 100,000 to 200,000 miles. It should be mentioned though that, despite the aging of EV batteries, a reduction in performance over the lifespan is not discernible to an electric vehicle owner because the batteries have a large capacity to begin with, with minor losses occurring without being noticeable.
Most common cell chemistries in EV batteries
We have earlier listed the six major EV battery components. Metals and minerals of these components are what give electric vehicle batteries their corresponding names.
Let’s take brief looks at the common chemistries of EV battery cells:
Lithium-ion batteries are the most common and most popular EV batteries today. The reason for their popularity is that they are cost-efficient and offer excellent energy storage. These batteries also come mixed with a variety of chemistries, such as lithium nickel cobalt aluminum oxide batteries and lithium-iron phosphate batteries which can be found in Tesla Model 3 cars.
Nickel Manganese Cobalt
Nickel manganese cobalt batteries provide a more balanced delivery of power and good energy storage.
Nickel Metal Hydride
Nickel metal hydride batteries were commonly found in the earliest forms of hybrid cars, including the Prius. While they have largely been replaced by lithium-ion batteries, you can still find nickel metal hydride batteries in the 2020 Toyota Highlander and a few hybrid electric vehicles.
Lithium sulfur batteries are particularly noted for their large energy storage capacity. The disadvantage to these batteries is that they need to be heated up first before they can generate enough power for an electric vehicle run. These batteries are more commonly found in EV buses.
Lead acid batteries were once the batteries of choice because they are low maintenance and are convenient to replace. Outclassed by lithium-ion batteries, lead acid batteries can now be mainly seen in low performance EVs like golf carts.
EV battery modules and pack designs
The beauty of EV battery design lies in the fact that the battery pack consists of modules, which in turn consists of individual battery cells, providing optimal flexibility for configuring various sizes of battery packs. More on the differences in the section below.
Single battery cells come in cylindrical, pouch, and prismatic forms. As we have mentioned above, these battery cells are combined to form EV battery modules.
EV battery cell, module and pack: key differences
The EV battery design is comprised of a hierarchy of elements enumerated below:
- EV battery cells – basic units of an EV battery. Each cell functions to store and deliver energy.
- EV battery modules – consists of a number of EV battery cells which are connected in series or in parallel. Each unit produces a certain voltage and meets a specific energy capacity.
- EV battery packs – consists of a number of EV battery modules which are connected in series or in parallel and enveloped in a robust casing. EV battery packs not only contain modules, but also other components for the monitoring of the cells and thermal management.
How EV battery packs are manufactured
EV battery packs are manufactured according to an EV battery design.
The process starts with a single cell. Two electrodes – the anode and cathode – are first installed within the casing. These electrodes are wrapped in thin, metal foils known as current collectors. The electrodes are then kept apart from each other by a separator to prevent short circuits. This assembly is then immersed within a liquid electrolyte prior to sealing in the casing. The cells are then subjected to moisture and leak checks which can cause corrosion and or fires/explosions.
Next, the single cells are assembled into EV battery modules. It is typical to find 12 battery cells per battery module, but this figure varies across EV makes and models. The modules are then stacked together within a robust housing to protect it from physical shocks. As with the individual cells, the modules are also subjected to tests for moisture seepage and leaks.
Last but not least, the modules are assembled manually into EV battery packs within a rigid housing. The process not only involves stacking the modules, but also ensuring that electrical connections are done correctly, and fine-tuning is observed.
While future EV battery technology does not see signficant changes to the overall battery pack design, research is more focused on replacing certain metals and minerals with others that are readily obtainable from the environment.
Laminated busbars: what are they and how are they used?
We cannot discuss electric vehicle batteries without briefly touching on laminated busbars.
Laminated busbars are multi-layered and composite structures which are connected with a platoon. They are used as the electric current distribution system to the main parts of an electric vehicle.
Laminated busbars are distinguished from other busbar technologies because of their great flexibility when it comes to customization, quick installation, reduced overall system costs, and greater performance reliability in EV batteries.
How to promote sustainability in designing EV batteries
Future EV battery technology is focused on finding materials that can easily be obtained from the environment or cost-effectively reused. One of the best sources of materials are old batteries. Old batteries are brought to recycling plants where they are shredded and important metals such as lithium, aluminum, and copper are obtained from the electrodes. A sustainable EV battery also promises to do away with cobalt, which is toxic and can only be mined in the Congo.
In manufacturing EV batteries, companies like Interplex are making great strides in interconnect systems which guarantee improved energy distribution and storage in an EV. Other companies are looking into improving the charging time of an EV battery, from a number of hours to just a few minutes.
Indeed, there is much to look forward to in the near future for electric vehicle batteries, which can hopefully drive costs to more affordable levels.