VW ID 4 82kWh Battery

A look at the 2021 VW ID 4 82kWh battery pack. This battery pack architecture is used across a number of vehicles under the VW family umbrella and in a number of sizes. Hence, although this says the ID 4, this is the 82kWh battery design used by Skoda and Seat amongst others as this is the Volkswagen MEB Battery Pack ID Family.

VW ID4 skateboard image

Metrics

  • Gravimetric Density
    • Energy = 168 Wh/kg
    • Power = 341 W10s/kg
  • Usable Energy = 77 kWh (total = = 82 kWh)
    • SoC Window = 93.9%
  • Nominal Voltage = 350.4 V
    • Voltage Range = 403.2 V to 240 Min V
  • Nominal Capacity = 234 Ah
  • Total number of cells = 288
    • Configuration = 96s3p
  • Pack Internal resistance (estimated from cell data)
    • 0.05952 Ω10s
    • 0.06752 Ω30s
  • Main Fuse Rating = A
  • Peak Power = 166.7 kW10s

Structure

The pack enclosure is described [1] as: The battery housing is made of aluminium. Reinforcements have been installed inside the housing to provide the battery modules with the best possible protection in the event of an accident, both in the longitudinal and the lateral directions. There are additional lateral reinforcements below the housing. The housing is surrounded by solid extruded aluminium profiles.

  • Pack Mass = 489 kg
    • Cell Mass = 309 kg
    • Pack-Cells = 180 kg
    • Cell to Pack Mass Ratio = 63.2 %
  • Pack Dimensions = 1820 mm x 1450 mm x 140 mm
    • Estimated Volume = 369.46 litres
  • Enclosure Materials = Aluminiun/Aluminium
  • IP Rating = IP6K7
underside of ID4 with battery removed

The battery is an integral part of the vehicle structure and crash system [1]: “Make sure nobody enters the vehicle after the high-voltage battery is removed because the battery contributes to the overall body rigidity. Once the high-voltage battery has been removed, there is a risk of vehicle body damage due to distortion.”

This shows the level of structural integration between battery and body in a ground up pure electric vehicle design.

The pack enclosure uses extrusions around the perimeter and castings that run across the inside of the pack. These castings reduce in height in the centre of the pack as the HV system and the local CSCs run down the central spine.

VW ID4 battery pack
Image from Munro Live [4]

Thermal Design

VW ID4 cooling plate

The cells are inside an aluminium module case, these are then in an aluminium enclosure and the cooling plate (Heat SInk) fits under the enclosure. This keeps all of the coolant fluids away from the inside of the enclosure. The next image shows the coolant connections, these are connected to the outside pack frame and at the opposite end to the HV and control connections.

The following image [5] shows the cooling channel a smaller capacity ID3/ID4 battery pack. This particular pack has had some damage to the underside and cooling channels.

Image from Flying Tools [5]
VW ID4 battery cooling channels

A section of the cooling system from the ID4.

The cooling plate is Rivtac nailed to the extrusions with a butyl seal.

This is a very robust way of avoiding cooling fluid and HV mixing. However, this system is also heating and cooling the pack enclosure and hence the environment. This means it will not be very efficient.

VW battery coolant connections
Image from Munro Live [4]

However, this does mean there are a lot of layers between the cells and the heat sink. Also, this means the pouch cells are cooled on their long bottom edge.

VW ID4 cell cooling schematic

The schematic shows a section through 3 cells, thermal interface material (TIM) in green in the module, the module case, more TIM (pink) between the module and pack case, the pack case and coolant channel under the case.

  • Improved cell design and more optimum for cooling.
  • Single outer cell wrap reduces distance to cooling plate and lowers z-height.
  • Tortuous thermal path between cells and coolant:
    • Aluminium module base and TIM used to thermally connect cells to module case.
    • TIM between module base and pack enclosure.
  • Cooling plates underneath the pack and thermally connected to the enclosure.
    • Robust to coolant leaks.
    • Significant heat loss and gain to environment.
    • Increased risk of underside coolant damage.

This post has been built based on the support and sponsorship from: Eatron TechnologiesAbout:EnergyAVANT Future MobilityQuarto Technical Services and TAE Power Solutions.

The heating and cooling limits [1]:

  • < 8°C (46°F): heating by the PTC Heating Element
  • > 35°C (95°F) (in vehicle operation): cooling by the heat exchanger or heat condenser
  • > 30°C (86°F) (during charging): cooling by the heat exchanger or heat condenser

The vehicle has a heat pump and a normal radiator, thus allowing the vehicle to optimise the thermal energy requirements.

HV and Control

VW ID4 battery and description of the parts

The pre-charge function of the battery pack is done by the DC-DC converter that operates between the HV battery and the 12V battery. This DC-DC can operate bi-directionally and hence can lift the system voltage to that of the battery pack prior to closing the main contactors.

Note the module to module busbar design.

Image from Munro Live [4]

The HV connectors, control connection, low voltage connector and the pack breather are all moulded in one part and fixed into one end of the battery pack. Note that the connectors are protected by the outer extrusion to some extent and this will reduce damage to them in the logistics and assembly plant.

VW ID4 connectors
Image from Munro Live [4]

The VW ID4 manual [1] states:

  • The insulation monitoring checks the electrical isolation of the high-voltage potentials to the chassis. When the value falls below a threshold of 510 kΩ, a yellow warning lamp illuminates on the instrument cluster.
  • A red lamp appears when the value falls below 90 kΩ.

Module

  • 24 Cells/module
  • 30kg
  • Module Gravimetric Energy Density = 228 Wh/kg

It should be noted that in the smaller 62kWh battery pack the cell configuration inside the module is different and that the modules can only be distinguished by the part numbers.

VW ID4 MEB module
Inside the VW LG Chem module

Inside a VW MEB module made by LG Chem [6]. This particular module appears to be from the smaller pack as it was configured as a 2p6s. However, the main structure and case are the same.

The cells are thermally connected to the base of the module with a thermal interface material.

The cell tabs have been positioned towards the cooling plate. This helps with temperature uniformity as heat generated where the electrodes all get connected to the tabs will have a shorter thermal path to the cooling plate.

Cell

  • LG Energy
  • Chemistry = NMC712
  • Pouch Format
  • Nominal Capacity = 78 Ah
  • Nominal Voltage = 3.65 V
    • Nominal Energy = 285 Wh
  • Mass = 1.101 kg
  • Cell Gravimetric Energy Density = 259 Wh/kg
  • Cell Resistance, DCIR
    • 0.00186 DCIR [10s 50% 25°C)
    • 0.00211 DCIR [30s 50% 25°C)

References

  1. The High-Voltage System in the ID.4, Self Study Program 811213, VW, 2021
  2. Volkswagen ID.4, WikiPedia
  3. The VW ID4, Volkswagen
  4. 2021 Volkswagen ID.4: Battery Teardown, Munro Live, YouTube
  5. Vw id3 id4 battery thermal management, Flying Tools, Youtube
  6. Open up a VW id3 id4 lithium battery module, Flying Tools, Youtube

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