• EV Batteries
• Battery basics
• Cell Chemistry & parts
• Cell formats
• Battery pack & configuration
• Battery Management System
• Thermal management
• Cell balancing
• Charging
• Degradation
• Buffer
• Manufactors
• Warranty

Battery pack & configuration

The battery system combines many cells and other control electronics into a full battery to power the EV.

Battery Configuration

In an electric vehicle (EV), the battery configuration refers to the arrangement of individual battery cells within the battery pack. The battery configuration can affect the voltage, capacity, power output, and other aspects of the battery pack and the overall vehicle performance.

The most common configuration for EV batteries is a series-parallel hybrid configuration. In this configuration, multiple cells are connected in series to increase the voltage of the battery pack, and multiple groups of series-connected cells are then connected in parallel to increase the overall capacity of the battery pack.

The series connection of cells increases the voltage output of the battery pack, which is important for providing the necessary power output to drive the vehicle. The parallel connection of cell groups increases the battery pack’s capacity, which is essential for storing the energy required to drive the car to a desired range.

Example Audi Q8 e-tron 55

The diagram below shows the configuration of a battery module from Audi Q8 e-tron 55. This module contains 12 battery cells, four of which are mounted in parallel, and there are three groups of this parallel configuration in serial.

Each cell has a nominal voltage of 3.6667 volts and a capacity of 72 AH.

Three cells in serial give a module voltage of 11 Volt. 4 x 72AH in paralell gives a total module capacity of 72 x 4 = 288 AH. Q8 e-tron 55 has a total of 36 modules in serial. 36 x 11 volts gives 396 volts for the pack. 396 x 288 = 114 kWh gross capacity.

The specific battery configuration used in an EV depends on a variety of factors, such as the desired range, power output, and overall vehicle weight.

400 or 800 volts?

Manufacturers typically configure the packs to be around 400 volts or 800 volts.

A higher voltage battery configuration, such as an 800-volt system, can offer some advantages over a lower voltage 400-volt system but also has potential drawbacks. Here are some of the pros and cons of each configuration:

Pros 400 Volt package

More mature technology: 400-volt battery systems have been around longer and are more widely used in electric vehicles, which means they are more proven and reliable.

Lower cost: Because they are a more established technology, 400-volt battery systems tend to be less expensive to produce than higher voltage systems.

Widely available charging infrastructure: There are many public charging stations that support 400-volt charging, making it easier to find places to charge your EV.

More available cell configurations 400 Volt packs can be configured in more ways giving the manufactor more cell options.

Cons 400 Volt package

Slower charging: A 400-volt battery system typically requires longer charging times than an 800-volt system, which can be a disadvantage if you need to charge your vehicle quickly.

Limited power output: 400-volt battery systems may not be able to deliver the same level of power output as an 800-volt system, which could limit the acceleration and performance of the EV.

Heavier: A 400-volt battery system may require thicker cables to support same charging speed.

Pros 800 Volt package

Faster charging: An 800-volt battery system can support faster charging times than a 400-volt system, which means you can charge your EV more quickly.

Higher power output: An 800-volt battery system can deliver more power output, which can provide better acceleration and performance, but in reality the most powersfull evs are 400 Volt. So this is not a real benefit.

Lighter weight: An 800-volt battery system may require thinner cables to support high speed charging.

Cons 800 Volt package:

Limited charging infrastructure: Fewer public charging stations currently support 800-volt charging, which means it may be harder to find places to charge your EV at full speed.

For example, the largest charging network, the Tesla Supercharger network, charges at a maximum of 500 Volts. Charging an 800-volt car on these chargers requires that the EV converts the charger voltage to 800 volts, and conversion typically limits the charging speed substantially. The manufacturers use Different techniques for this conversion. See the charging chapter for details.

Here are some configuration examples

Battery pack designs

Cell-to-module

Cell-to-module (C2M) is a technology used in electric vehicle (EV) battery packs that allows for a more modular and scalable design compared to traditional battery pack designs.

In a traditional EV battery pack, individual battery cells are connected to form a module, and multiple modules are then connected in series and/or parallel to form the complete battery pack. This can be complex and expensive, especially in large battery packs, and may require extensive wiring and cooling systems to ensure even charging and discharging of the cells.

With C2M technology, multiple battery cells are assembled into a single, self-contained module with integrated electronics and cooling systems. The modules can then be easily connected together to form the complete battery pack. Each module has its own BMS (battery management system) that monitors and controls the charging and discharging of the cells within the module, allowing for more precise control and monitoring of the individual cells.

C2M technology has several advantages over traditional battery pack designs. It can simplify the overall design of the battery pack, reduce wiring and cooling requirements, and allow for greater flexibility in the overall pack design. It can also improve the overall reliability of the pack, since each module is self-contained and faults can be detected and isolated more quickly.

Cell-to-pack

Cell-to-pack (CTP) batteries are a new type of battery technology that eliminates the need for battery modules by integrating the cells directly into the pack.

This technology is being developed by several companies such as Tesla, BYD and CATL.

BYD Blade and CATL Qilin are two examples of CTP batteries. The main difference between these two batteries is their cooling system.

BYD Blade uses a liquid cooling system while CATL Qilin uses a structural cooling system. The structural cooling system is more efficient than the liquid cooling system used in BYD Blade.

The benefits of CTP batteries include higher energy density and lower cost compared to cell-to-modules.

Structural battery pack

A structural battery pack is a type of battery pack that is created a way that the pack iteslf becomes a structural component of the EV.

This approach can reduce the EV weight becaus by removing duplicate structure between the pack and the veichle structure because the battery pack itself becomes a part of the veichle structure.

This can improve the EVs overall performance and efficiency.

Structural battery packs are still a relatively new concept, but they are being explored and developed by a number of companies and research institutions.

They have the potential to revolutionize the design of electric vehicles and other devices by reducing weight and complexity, improving performance, and making it easier to integrate battery technology into a wide range of applications.

Currently it is only Tesla Model Y that have structural packs. According to Tesla, this solution presents many advantages, such as a great reduction in the number of parts used in both the battery pack and the car.

More importantly, the company said the new cells together with the structural pack are expected to increase the Model Y’s range by 16 percent and decrease the overall weight of the car by 10 percent, resulting in improved acceleration and handling.

The below video show a detailed analysis of the pack by Munro & Associates.

Energy density at the battery pack level

The following table shows how pack density have varied over time between some example battery packs.

If you want to get the details about more packs we recomend BatteryDesign.net