Structural High Voltage Battery

Last updated: December 11, 2024

Overview

The high voltage (HV) battery is the primary energy storage device in the vehicle. Its main purpose is to provide power to the powertrain for all vehicle operations.

The HV battery hosts several key components of the powertrain that are vital for vehicle functions like driving, charging, and providing power to the vehicle low or medium voltage (referred to as LV or MV) systems.

Warning

The HV battery has a lot of energy stored in a small volume. Use extreme care when handling HV batteries.

Location of the High Voltage Battery

The HV battery is mounted to the chassis bottom for easy removal and installation, improving vehicle dynamics with a lower center of gravity.

The structural HV battery is designed to be part of the vehicle body and provides structural properties to the chassis and body of the vehicle. The structural HV battery enclosure is integrated with the Body-in-White and provides frontal and side impact backup structure along with interior seat mounts.

The HV battery not only provides rigidity to the chassis for vehicle dynamics and vehicle impact response, but it also acts as the floor of the vehicle. The seats, carpet, center console, harnesses, thermal duct and other interior trim are mounted directly onto the structural HV battery.

1. Front of vehicle 2. Rear of vehicle 3. HV Battery
HV Battery Location

The battery pack is integral to the chassis, so removing it without first removing interior components can cause them to be pulled out with the battery.

When all the attached components are removed from structural HV battery, the HV battery looks similar to a non-structural HV battery from the outside (except for the mounts of the seat rails).

Pack Generations

The Cybertruck HV battery is referred to as Gen 4 pack.

Below are the different generations of Tesla HV batteries:

HV battery Generation	Applicable Models
Gen 1	2012-2020 Model S 2015-2020 Model X
Gen 2	Model 3 Model Y (Non-Structural and structural HV batteries)
Gen 3	2021+ Model S 2021+ Model X
Gen 4	Cybertruck

The Gen 4 HV battery was introduced on the Cybertruck. For launch in 2023, there is a single configuration of the Gen 4 HV battery for both Long Range (Dual Motor) and Tri-Motor configurations that weighs ~730 kg.

Pack Architecture

The HV battery consists of the two distinct sections:

• The module platter
• The Ancillary Bay
• The rear access service panel
• The pyro-disconnect area

The HV battery module platter includes battery cells and thermal management components, and the Ancillary Bay holds electronic components known as "high voltage devices." For more details, see HV Devices Theory of Operation.

1. Ancillary Bay 2. HV battery Platter 3. Pyro-Disconnect Cover
Cybertruck Structural HV Battery

Battery Platter

The HV platter is the large area of the battery that is below the Ancillary Bay and inside the enclosure. It contains the cell-arrayscell-arrays

The platter contains all the cells which have a minimum voltage of 2.5V4.2V192, the HV battery has a minimum voltage of 480V and a maximum of 806V when the HV battery is in series mode (nominal state)

The cells used in the HV battery have 94Wh125 kWh

Ancillary Bay Theory of Operation.

1. Top Cover 2. Ancillary Bay Cover 3. Platter with 4 Cell-Arrays 4. Ancillary Bay
Main sections of the HV battery (Cover Lifted)

Ancillary Bay

The Ancillary Bay contains most of the HV electronics in the HV battery used to control the HV system of the vehicle. This includes:

• Powering up the HV system of the vehicle
• Charging the vehicle HV battery
• Providing power to the mid- cell-arrays

The Ancillary Bay is located in the rear of the HV battery and the vehicle.

There is a service access cover allowing quick access to the HV devices within the Ancillary Bay. The cover is removable and can be accessed by removing a section of the truck bed and moving the suspension air tank to the side.

1. Ancillary Bay Fasteners 2. Ancillary Bay Service Cover 3. HV Components in Ancillary Bay 4. Seal / Gasket of the Ancillary Bay
Cybertruck Ancillary Bay

The Ancillary Bay contains:

HV Device	Purpose
Power Conversion System (PCS)	Converts AC to DC when charging Converts DC to DC to support themid- Includes the quad core processor to manage high voltage software functions Cybertruck HV battery has 2 shunts (needed to measure current in each subpack when the HV battery is in parallel mode for DC charging at 400V)
HV Pyro-disconnect	Disconnects HV when specific HV failure is detected (previously called a pyro-fuse) Cybertruck HV battery has 2 pyro-disconnects (needed to individually disconnect subpacks when the HV battery is in parallel mode for DC charging at 400V)
Charge inlet connector	Connects PCS input to the charge port
HV fuses	Switched PCS HVDC input/output -60 A - 1000 VDC -60 A - 1000 VDC Unswitched PCS HVDC input/output-15A - 1000 VDC Optional Accessory - 30 A - 1000 VDC

Most of these HV devices in the Cybertruck Ancillary Bay are part of the device cluster. See LINK The HV devices are places as shown below in the Ancillary Bay:

1. Ancillary Bay service cover 2. PCS coolant hoses 3. PCS2 4. AC junction box 5. Device Cluster 6. Ancillary cover seal / gasket 7. HV busbars
Main components of the Cybertruck Ancillary Bay

The rendering below shows the Ancillary Bay as seen when the cover is removed:

1. PCS2 2. High Voltage Controller (part of the device cluster) 3. Fast Charge contactor assembly 4. Charge inlet 5. Most Negative cell-array terminal (Cell-Array 1) 6. AC junction box 7. Most positive cell-array terminal (Cell-Array 4) 8. Device Cluster
Cybertruck Ancillary Bay with cover removed

The rendering below shows the Ancillary Bay without the ancillary or device cover to see location of most HV devices:

1. PCS2 2. PCS2 coolant inlet 3. PCS2 coolant outlet 4. Pyro-disconnect on positive leg in series mode or positive side of the high side pack in parallel mode 5. Most Negative cell-array terminal (Cell-Array 1) 6. AC junction box 7. Most positive cell-array terminal (Cell-Array 4) 8.Device Cluster 9. Pyro-disconnect on negative leg in series mode or negative side of the low side pack in parallel mode 10. DPDT with housing off 11. HV receptacle for accessory 12. HV receptacle to compressor - CMP-HV-AT-HVBATT 13. Positive contactor 14. Fast Charge contactor assembly 15. Charge inlet 16. Positive DC link bus bar 17. Negative DC link busbar
Cybertruck Ancillary Bay with cover, tray and cluster housing removed

The pyro-disconnect is accessible after removing the entire Ancillary Bay cover when the pyro-disconnect trips and needs replacement (usually after any airbag or pretensioner deployment).

A dedicated cover under the vehicle allows for easy access to the pyro-disconnect, enabling replacement without removing the HV battery or Ancillary Bay cover, often after any airbag or pretensioner deployment.

High Voltage Interfaces

The HV battery integrates the functionality of the on-board charger, DCDC converter, HV distribution mid-

1. Logic connector to vehicle 2. HV Charge cable connector 3. HV Plug for AC outlet cable to truck bed outlets 4. HV Plug for AC outlet cable to cabin outlets 5. HV Plug for Front Drive Unit HV cable (connector reference FDU-HV-AT-HVBATT) 6. HV Plug for Rear Drive Unit HV cable (connector reference RDULEFT-HV-AT-HVBATT) 7. HV Plug for Right Rear Drive Unit HV cable (connector reference RDURIGHT-HV-AT-HVBATT) 8. HV Plug for compressor HV cable (connector reference CMP-HV-AT-HVBATT) 9. HV Plug for accessory HV cable (connector reference ACC-HV-AT-HVBATT) 10. Pressurized HV battery air inlet from air suspension tank 11. Pressurized HV battery air outlet from Ancillary Bay to platter 12. Ancillary coolant port outlet 13. Ancillary coolant port inlet 14. Pressurized HV battery inlet from Ancillary Bay
HV battery interfaces

Cell-Arrays

Specifications

The HV battery is made of 4 independent cell-arrays installed length wise in the platter. The cell-array contains the cells of the HV battery and it is the source of energy and power for the vehicle. Each cell-arraycell-array

Each cell-array is made of 48 bricks in series which sums up to a voltage of 172V per cell array.

Operation

Cells

Cells are the source of energy and power for the vehicle.

The HV battery has an internal structure of lithium ion cells linked together in combination of parallel and series to reach the desired level of energy and power required.

The lithium ion cells have a high energy density (Wh/kg), about 2 to 3 times the energy density of a nickel-metal hydride battery and 6 times the energy density of lead acid battery. Lithium ion cells are agnostic to charge and discharge patterns. When not in use, lithium ion cells self-discharge and have a flat discharge curve, meaning they have linear power capability even at half charge level.

Rechargeable batteries perform reversible electrochemical reactions at the battery’s positive and negative electrodes. The battery is charged by applying an electric current.

During discharge, lithium ions de-intercalate from the negative electrode and move through a separator to intercalate in the positive electrode. When charging, the reverse occurs. Lithium ions de-intercalate from the positive electrode and move through a separator to intercalate in the negative electrode.

4680 cell

The cells used in the HV battery have a 4680 (Gigafactory Austin) or Blade style (Gigafactory Berlin)

HV battery Generation	Configuration	Cell Type	S-Count	P-Count	Total Cells in Pack
Gen 4	Long Range	4680	192	7	1344

Bricks in Bandoliers

A brick is a group of cells connected in parallel. Linking cells in parallel adds current from each cell to increase current capability and the amp hour count (the unit for measuring the energy capacity of a battery).

The bricks are connected in series in a cell-array to increase voltage. The cell-arrays are also chained together in series to further increase voltage and power capability.

Each brick is spread on the entire width of the cell-array for even repartition of current among the cells. Seven cells from one brick will be connected to the cell collector via their positive terminal and seven cells from the next brick will be connected to the cell collector via their negative terminal.

1. First brick 2. Next brick 3. Cell-Array
Brick Layout in a Cell-Array

A bandolier refers to one or two strings of cells against a cooling tube. A cell-array is made of four bandoliers.

The cells in the bandolier are positioned vertically and oriented in the same direction (one brick with anode facing up and the next brick with anode facing up).

Cells are bonded together to the cooling tube with an adhesive. The cooling tubes are powder coated with an insulating layer to prevents short between the can of the cells and the cooling tube. Such a short would create isolation degradation to chassis via the coolant running in the cooling tubes.

1. End of cooling tube 2. Cells stuck to each side of cooling tube
Single Bandolier

Cell-arrays are separated by a cross member running length wise in The HV battery. There are three inner longitudinals between each cell-array and two outer longitudinals between the outer cell-arrays and the edge of the battery. The outer longitudinal protects the cell-arrays during side vehicle impacts.

The top of the cells of each brick are spot welded to two current collectors. The center button of the cell is the positive terminal of the cell, and the outside can of the cell is the negative terminal.

• One current collector is connected to two bricks (positive of one brick and negative of the other one).
• A single collector will be connected to 14 cells.
• Half of a collector will be connected to the can of the cells (anode) and the other half are connected to the center tab (cathode).

The current collector performs the following functions:

• Electrically interconnects cell-arrays in a series of parallel groupings,
• Distributes current between all cells in a given parallel grouping,
• Allows terminal voltage sensing, at a single point, for all cell in a given brick,
• Conducts peak and continuous operating currents between each cell and array,
• Fusing protection for HV shorts.

The figure below shows the location of the cells, brick, and cell-arrays in the HV battery.

1. Top Cover 2. Battery Cell 3. Bandolier 4. Cell-Array 5. Inner Longitudinal (3) 6. Outer Longitudinal (2)
HV Platter - Cell-Array to cell

Cell and Brick Numbering

Cell and brick numbering is the link between software and the physical pack. The numbering hierarchy in the structural HV battery is as follows:

1. Cell-Arrays are numbered from 1 to 4.
2. Bandoliers in each cell-array are numbered from 1 to 4 .
3. Each cell within a bandolier is numbered from 1 to 96

Numbering of Cell-Array, Bandolier, and Cells in the HV battery

High Voltage Chain

Current and power accumulate along the cell-array, beginning at the first brick on the most negative end and growing to the positive end of the array, with HV terminals at each end to facilitate connection.

Note

The front terminals are designed to fuse under short circuit events at the cell-array level.

For detailed information on how the voltage builds up in the HV battery, refer to the HV Architecture Theory of Operation

High voltage build up can occur in either:

• Series Mode for full HV battery voltage (~800V) operations
• Parallel Mode for half HV battery voltage (~400V) operations

The Dual Pole Dual Throw (DPDT) in the Ancillary Bay connects the cell-array either in Series or Parallel mode.

Overview of HV Built Up and Distribution in Series and Parallel modes

Series Mode is the default state of the HV battery that is used for driving, AC charging, support mode, and more. Series Mode is not active during DC fast charging on a DC charge that is unable to provide 800V. Voltage build-up within structural HV battery in Series Mode goes as follows:

1. Voltage starts at the most negative terminal and builds up through Cell-Array 1 to the front of the HV battery.
   
2. Voltage jumps to Cell-Array 2 via HV jumper busbar at the front of the HV battery.
   
3. Voltage builds up through Cell-Array 2 to Ancillary Bay where DPDT shorts to Cell-Array 3.
   
4. Voltage builds up though Cell-Array 3 and Cell-Array 4 to reach 800V on the most positive terminal on right end side of the Ancillary Bay
   

Overview of HV Built Up and Current Flow in Series Mode (800V)

For DC fast charging when unable to provide 800V, DPDT will switch to Parallel Mode where:

• Cell-Arrays 1 and 3 are in series
• Cell-Arrays 2 and 4 are in series

Those pairs of cell-arrays in series are then connected in parallel.

Overview of HV Built Up and current flow in parallel mode (400V)

Warning

When in parallel mode, DC link negative is directly connected to the negative side of Cell-Array 5 (even if negative pack-contactor is open) and DC link positive is directly connected to the positive side of Cell-Array 4 (even if positive pack-contactors is open). However, those potentials are from two subpacks isolated from each other. There is no path for current as long as isolation is nominal between those two subpacks.

A voltmeter will probably indicate a voltage between DC link positive and negative because the HVC trying to satisfy grounds, but no current can flow.

If an isolation breach was present, DC link negative and positive should be considered as pack negative and positive with ability for current to flow through was some resistance or short introduced between the two.

1. Most negative terminal with bolted connection to the always hot side of the negative contactor. 2. Voltage builds up from most negative (rear of HV battery) terminal to top of Cell-Array 1 at front of HV battery 3. Front jumper from Cell-Array 1 to Cell-Array 2 4. Voltage builds up in Cell-Array 2 from front to rear 5. Voltage builds up in Cell-Array 3 from rear to front 6. Front jumper from Cell-Array 3 to Cell-Array 4 7.Voltage builds up in Cell-Array 4 from front to rear 8. Terminal of Cell-Array 3 connected to what is now a negative busbar 9. Pyro-disconnect for 2 cell-array subpack (Cell-Array 1 and 3)on the negative side leg 10.DPDT in parallel position (not shorting the 2 pyro-disconnects like in series mode) 11. Negative busbar collector connecting to battery side of negative contactor 12. Terminal of Cell-Array 4 connecting to the positive contactor 13. Terminal of Cell-Array 2 connecting to DPDT via pyro second pyro-disconnect 14.Positive side of DPDT in parallel mode 15. Positive leg of always powered side connecting to battery side of positive contactor
Ancillary Bay HV Distribution in Parallel Mode

Serviceability

Cell-Arrays are not serviceable because they are embedded within the platter area, making them inaccessible due to the structural HV battery's bonded top and bottom enclosures.

Battery Management Board

Specifications

A BMB is a Printed Electrical Circuit Board (PCBA) with various electrical components on it. The primary functions of a battery monitoring board (BMB) are:

• Measuring voltages of the bricks in a cell-array
• Measuring temperatures of cell-arrays in one or several locations
• Balancing bricks charge level amongst other bricks

BMBs are connected to both sides of each brick in a cell-array.

The wires linking current collectors to BMBs are consolidated into a flexible ribbon cable called the Voltage Sense Harness (VSH).

1. BMB Unit 2. BMB PCBA (plastic housing removed) 3. Voltage Sense Harness (VSH)
Battery Monitoring Board with VSH

BMBs have two thermistors mounted directly on the PCBA close to where the bandolier cooling tubes contact the BMB PCBA. The temperature of the cell-array can be measured without requiring extra wiring between BMBs other locations on the cell-array.

BMBs connect to each other via a daisy chain which itself is connected to the high voltage controller (HVC). Temperature and brick voltage measurements from BMBs travel on this daisy chain to the HVC. If the daisy chain is interrupted or cut anywhere, the data from BMBs can travel the other direction to the HVC.

1. BMBs at End of Each Cell-Array 2. HVC 3. Passthrough Connector Between Ancillary Bay Platter 4. Voltage Sense Harnesses (VSH)
Connection of the Daisy Chain to the HVC

BMBs are equipped with an analog to digital converter (ADC) to get the brick voltages and temperatures into a format that can be sent on a digital communication protocol. They also embed a multiplexer to send each measurement in sequenced order on the daisy chain.

BMBs contain one power resistor and Field Effect Transistor (FET) per brick. The FET enables a resistor to be connected in parallel with the brick, allowing for controlled energy dissipation and balancing of brick charge levels in the HV battery. BMBs only perform this passive balancing and do not charge the least charge bricks (known as active balancing).

Each cell on the picture is equivalent to a brick
Passive Balancing with Discharge of Most Charge Bricks

Operation

The BMB functions of measuring cell-array voltage and temperature and balancing brick charge levels are critical to operating the HV battery and the vehicle. A BMB not operating as expected can prevent vehicle charging or starting, and may also cause reduced power or graceful power-off with a 30-second warning while driving to pull over before contactors open.

BMBs continuously monitor temperatures and brick voltages during charging, driving, and mid-voltage system support. When the vehicle is asleep, the HVC wakes the BMBs every 10 minutes for them to report measurements and ensure brick health.

BMBs will balance the bricks when the HVC enables balancing. The HVC enables brick balancing only when the charge level of bricks has enough charge or voltage difference, and the least charged brick is above a certain threshold.

BMBs don't have embedded advanced micro processing capabilities. Their duty is to sense voltage, temperatures, and be able to put a resistor across a brick for balancing. All the processing happens in the HVC, which requires the measurements provided by the BMBs. To get the data from BMBs to the HVC, there is a daisy chain leaving the HVC, going through all BMBs in series and back into the HVC.

The daisy chain communication is bi-directional. If the daisy chain is cut anywhere, all BMBs can still communicate to the HVC.

Serviceability

BMBs not serviceable because they are embedded within the platter area, making them inaccessible due to the structural HV battery's bonded top and bottom enclosures.

High Voltage Battery Thermal Management

Specifications

The HV battery uses liquid based thermal systems to keep battery cells at their optimized temperature and to control heat generated during conversions between AC/DC and AC/DC power. The thermal systems are split between cooling the Power Conversion System (PCS) and the cells within the cell-arrays.

Power Conversion System Thermal Loop

The PCS cooling loop consists of:

• Coolant passthrough to connect external coolant lines to the ones going to the PCS inside the HV battery.
• Inlet coolant hose bringing external coolant to the PCS.
• The PCS cooling plate on which electronic components of the PCS are mounted.
• Temperature sensors on the PCS Printed Electrical Circuit Board (PCBA).
• Outlet coolant hose to push the warm coolant back out to the external cooling system.
• Temperature sensor at the coolant inlet into the HV battery.

The PCS coolant inlet and outlets are located at the front of the HV battery directly through the platter cover.

1. PCS coolant inlet passthrough 2. PCS coolant outlet passthrough 3. PCS coolant outlet hose 4. PCS coolant inlet hose 4. Power Conversion System ECU
PCS Coolant Loop

Cell-Array Thermal Loop

The platter cooling system consists of:

• Coolant passthrough to connect external coolant lines to the ones to the cell-arrays.
• Inlet coolant manifolds to split the coolant flow to all the cooling tubes of the HV battery.
• Cooling tubes thermally connecting the cells to the coolant.
• Outlet manifolds to collect the coolant back from all the cooling tubes .
• Outlet coolant hose to push the coolant back out to the external cooling system.
• Temperature sensors on each BMB.

The platter coolant passthrough is located at the front of the HV battery, in the middle of the HV battery width wise. The coolant passthrough carries both the inlet and outlet side by side.

1. Coolant ports for the platter 2. Coolant inlet into the HV battery 3. Coolant outlet outside of the HV battery
Coolant Ports of the HV Battery Platter

Operation

Power Conversion System Thermal Loop

The PCS requests a desired temperature to the right Etherloop generalized gateway 3 (EGGRIGHT3). EGGRIGHT3and the supermanifold vehicle controller (VCSUPER) aggregate all the component temperature requests and appropriately set the pumps speeds and the coolant loop state.

The coolant coming from the PCS inlet passthrough will travel in the PCS cooling plate where heat will be transferred from the PCS electronics to the coolant. The coolant, from the hot electronics, will exit the PCS to get back to the vehicle cooling system where heat will be transferred to the outside air of other components that requested heat.

Cell-Array Thermal Loop

The HVC calculates the desired coolant temperature based on brick State of Charge (SOC), temperatures, and vehicle state, sending it to EGGRIGHT3. EGGRIGHT3 and VCSUPERaggregates this data to control pump speeds and coolant flow. The output is either hot or cool coolant traveling through the cooling tubes of the platter.

In the cell-arrays, each cell has about a third of its surface in contact with a cooling tube. The entire height of any cell contacts the cooling tube to ensure homogenous temperature along the cell.

Each cell-array has 4 length

The cooling tube is split in two height-wise, with the upper side being the inlet and lower side being the return. This circulation allows a more homogeneous heat exchange compared to a series pattern.

1. Input cooling connector 2. Output cooling connector 3. Separator splitting coolant flow in cooling tube
**Cell-Array

Coolant flows in a "U" shape inside each coolant tube, with the inlet and outlet on the same end of the module. This is shown with the red and blue arrows in the picture below.

1. Coolant passthrough from and to vehicle coolant loop 2. Coolant inlet to the HV battery 3. Coolant entering HV battery though the inlet manifold 4. Coolant flows through the bottom section of the cooling tube to the rear of the cell-array 5. Coolant makes a U turn in the cooling tube to end up in top section of the tube 6. Coolant flows through the top section of the cooling tube back to the front of the cell-array and HV battery 7. Coolant flows through the top section of the cooling tube back to the front of the cell-array and HV battery 8. Coolant going to passthrough from cooling tube via the outlet manifold 9. PCS 2 coolant loop
Coolant Flow (Showing a Cooling Scheme with Blue Input Arrows)

Serviceability

The PCS cooling system is serviceable:

• The PCS can be replaced if the cooling plate has a blockage or is leaking.
• The coolant hoses from the Ancillary Bay cover to the PCS are also replaceable if damaged.
• The coolant hoses and passthroughs set up on the HV battery avoids any spillage in the Ancillary Bay upon disconnection and avoid having to drain coolant for other service actions in the Ancillary Bay that do not involve PCS.
• Service can disconnect coolant connections at the passthrough (coolant will leak outside) and plug the passthroughs. From there, the PCS and with the coolant hoses connected can be removed as one unit preventing any spillage.

The platter thermal system is not serviceable because its components are embedded within the platter area, making them inaccessible due to the structural HV battery's bonded top and bottom enclosures.

Overpressure / Overtemperature Dissipation

Specifications

The HV battery needs to be able to handle thermal runaway events internal to the HV battery in a controlled manner. Those events are sometimes caused by:

• Significant external damage to the HV battery causing cell penetration or deformation
• An internal coolant or other liquid flood. In rare cases, it can also be caused by some internal failures in the HV battery.

The HV battery features the following hardware to control runaways:

• Pack venting to allow controlled release of internal HV battery overpressure. The HV battery uses vents to allow the pressure in the enclosure to vent if pressure builds up inside the HV battery.

1. Four vent assemblies at the rear of the HV battery 2. Ancillary Bay 3. Vent section that disintegrates with heat 4. Cover which pops off with pressure 5. Breather
HV Pack Vents

• Flood ports to allow automated drainage of any liquids trapped in the HV battery. Flood ports open when liquid contacts the inside of the flood port on the HV battery side (and not when liquid contacts the section of the flood port sticking outside of the HV battery).

1. Flood port basket housing preventing blockage 2. Cellulose element 3. Spring load allowing the valve to shoot down when cellulose element dissolves 4. Flood port carrier 5. Valve pushed down in presence of liquid

The basket housing is designed to prevent anything from blocking the flow of liquid by catching any large debris that would otherwise flow into the hole and plug it.

Note

The flood ports of the platter are protected with a dust cover. See below.

1. Dust cover to protect the flood port 2. Flood port 3. Opening in the enclosure where flood port seats to let liquid out

1. Ancillary flood ports (3) 2. Flood ports (4) on all 4 corners of the platter enclosure
Flood Port Location

Operation

Pack Vents

If pressure builds up inside the HV battery, the vents are designed to open outward, allowing pressure to escape the enclosure if it builds up inside. It is a one-way vent, designed so that air or other environmental debris will not enter the HV battery. The vent will disintegrate under high heat. Once disintegrated, it creates a large opening to allow faster expulsion of high-pressure gases inside the HV battery.

The structural HV battery has a dedicated space under the cell-array for pressure and heat to escape to the rear vents, and electrical isolators between arrays to reduce propagation risk.

Flood Ports

Any long standing liquid inside the HV battery is concerning, it could overtime create soft short between cells that could generate uncontrolled heat. Flood ports automatically drain any liquid inside the HV battery to below cell-arrays. A flood port is a mechanical one way valve that opens in presence of liquid. It has a cellulose element that expands upon contact with liquid. This causes a plastic retainer to release a spring that opens the valve to let the liquid drain from the Ancillary Bay . The flood port design helps:

• Prevent hazardous pooling of fluid inside the HV battery volume.
• Seal against liquid/gas passage into the HV battery from outside.

The flood port is one time use, once it opens, it cannot close back and needs to be replaced. However, the flood ports are replaceable in service from the outside of the HV battery by twisting and pulling. It is likely that a plastic tab will break and fall into the HV battery, which is okay.

Serviceability

Both vents and flood ports are replaceable in service if damaged, missing or opened. They snap on to the enclosure from the outside of the HV battery (flood port require a twist before being pulled out)

Note

If it is suspected that a HV battery has liquid in the platter, service is responsible for draining the liquid as soon as possible.

To maximize drainage of the liquid, manually remove the 7 flood ports from the enclosure and let the vehicle / HV battery sit as flat as possible.

Warning

Unlike other type of HV batteries, do NOT tilt the HV battery to try to drain more liquid out.

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