Battery system

The battery system is the combination of many cells and other control electronics to a complete battery to power the EV.

Today this is most typical achived with the Cell2Module technology. Where cells are grouped in to modules that again are grouped in to a battery system.

In the future we will see cars witn Cell2Pack technologies where cells are put directly in to packs and even Cell2Car technology where cell are put directly in to the car. More about that later

Typical a battery pack consist of modules that consist of serveral cells.

Modules

Modules are a combination of cells. The number of cells in a module varies.

Module

LG battery module

Architecture

The cells inside a module can be connected different ways.

  • Serial connecting gives a higher voltage
  • Paralell connection gives a higher capacity.

Example 1

Below you see how modules on e-tron 55 are. There are 12 cells per module. They are grouped in 3 groups where 4 cells are connected in paralell. Then those groups are connected in serial giving it a 3 serial 4 paralell configuration (3s4p). With 60AH for each cell and a nominal voltage on 3.66 this module have a capacity on 240AH and 11 volts.

Battery

3s4p connection

Example 2

Below you see how modules on e-tron 50 are. There are 12 cells per module. They are grouped in 4 groups where 2 cells are connected in paralell. Then those groups are connected in serial giving it a 4 serial 2 paralell configuration (3s4p). With 60AH for each cell and a nominal voltage on 3.66 this module have a capacity on 180AH and 14.666 volts.

Battery

4s3p connection

Audi modules

| Module | No of cells | Config | Capacity AH | Nominal voltage | kWh | |—–|—–|—–|——|——| |e-tron 55 | 12 | 3s4p | 240AH | 11 volts | 2.640 kWh | |e-tron 50 | 12 | 4s3p | 180AH | 14.666 volts | 2.640 kWh | |e-tron GT | 12 | 6s2p | 129.2AH | 21.909 volts | 2.830kWh | |Q4 e-tron | 24 | 8s3p | 234AH | 29.16 volts | 6.825kWh |

Packs

Battery packs consist of several modules placed in a construction that is created to protect them and give them optimal conditions. Below you see an battery pack from Audi e-tron GT.

Batterypack

Batterypack with 33 modules

Typical the pack is placed at bottom of car.

Audi Battery packs

Today all Audi models uses Cell2Module technology

Battery pack configuration

Cell type Cells Modules Voltage Cell config Gross cap
e-tron 55 LGXN2.1 432 36 396 108s4p 95 kWh
e-tron 55*3 Samsung 432 36 396 108s4p 95 kWh
e-tron 50 Samsung 324 27 396 108s3p 71 kWh
e-tron GT E66A 396 33 723 196s2p 93.4 kWh
RS e-tron GT E66A 396 33 723 196s2p 93.4kWh
Q4 e-tron 50 LGX E78 288 12 350 96s3p 82 kWh
Q4 e-tron 40 LGX E78 288 12 350 96s3p 82 kWh
Q4 e-tron 35 LGX E78 196 9 350 96s2p 55 kWh
Q6 e-tron*1 LGX E78? 392? 16? 700? 192s2p? 110 kWh?
A6 e-tron *2 LGX E78? 392? 16? 700? 192s2p? 110 kWh?

Battery pack performance

In the table below you see the pack performance. See how Q4 have higher density even the cell itself does not have a better density.

Gross capacity Net capacity Max DC Charging Weight kWh/kg
e-tron 55 95kWh 86.5kWh 150kW 699kg 0.136
e-tron 55*3 95kWh 86.5kWh 150kW 699kg 0.136
e-tron 50 71kWh 64.7kWh 125kW 580 0.122
e-tron GT 93.4kWh 83.7kWh 270kW 630kg 0.148
RS e-tron GT 93.4kWh 83.7kWh 270kW 630kg 0.148
Q4 e-tron 50 82kWh 77kWh 125kW 493kg 0.188
Q4 e-tron 40 82kWh 77kWh 125kW 493kg 0.188
Q4 e-tron 35 55kWh 52kWh 100kW 344kg 0.160

*1 Audi Q6 details is not yet confirmed.

*2 Audi A6 details is not yet confirmed.

*3 From January 2021 Audi uses Samsung cells on e-tron 55

What is next for Audi?

The problem with todays approach with Cell2Modules is that the energy density on the battery system is much lower than on the cell level. This is because of all the structural elements in a battery that does not add any energy content to a battery pack.

To reduce this problem Volkswagen is moving to a Cell2Pack technology where Audi with its Artemis project will launch the first car with in late 2024.

The technology is based on putting the cells directly in to the pack increasing the energy density to the battery system. This reduces weight and increases capacity.

On March 15. 2021 the Volkswagen group that Audi is part of presented their strategy as part of Power day.

Cell to pack

Volkswagen Cell2Pack technology

Cell2Pack

Volkswagen Cell2Pack comparison

See the complete presentation.