BYD Battery Fire and Thermal Runaway: What the Official Response Guide Actually Requires

Why a Firefighter’s Document Is the Right Starting Point for a Workshop

The BYD Emergency Response Guide is written for firefighters and rescue crews. It is also the only document in which BYD states, in English, what happens when one of its battery packs is damaged — which is precisely the situation an independent workshop inherits when a customer tows in a flooded car or one that took a hit underneath.

The questions in a service bay are narrower than a fire crew’s, but they are the same questions. Does the car stay outside or come in? Who is allowed to touch it? How long before it can be moved? What does a BYD battery fire look like in its first thirty seconds? This page is the manufacturer’s own answer, filtered down to what a workshop actually needs. Because every current BYD pack is LFP, the behaviour described below is specific to LFP battery fire behaviour rather than the nickel-based chemistry most western guidance was written around.

Every Current BYD Pack Is LFP — That Changes the Fire, Not the Risk

BYD builds its current range around lithium iron phosphate. LFP is the more thermally stable of the two mainstream chemistries: it is genuinely harder to drive into thermal runaway than a nickel-rich cell, and it will not release oxygen from its own lattice as readily. That is a real safety advantage and BYD leans on it heavily.

It is not a free pass. A damaged LFP pack still holds a large amount of stored energy, and once a cell has been pushed into runaway the reaction supplies its own oxygen — which is why a battery fire is extinguished by cooling, not by smothering.

These are the pack ratings BYD publishes on its own rescue sheets, and the spread matters when you are standing next to the car:

Model	High-voltage pack	Low-voltage battery	Chemistry
Atto 2	300.8 V	12.8 V	LFP
Seal 6	268.8 V	12.8 V	LFP
Sealion 5	352 / 268.8 V	12 V	LFP
Shark 6	364.8 V	12.8 V	LFP
Seal / Sealion 7	550.4 V	12 V	LFP

Two observations that catch people out. First, the range is wide — a 550.4 V Seal pack is roughly double the voltage of a Seal 6 at 268.8 V, so PPE and tool ratings cannot be carried over between models by assumption. Second, the 12 V battery on most of these cars is itself an LFP unit at 12.8 V, not a lead-acid battery at 12.6 V. That matters the moment you are testing it.

Coolant Leak Is the Trigger You Can Actually See

The pack is floor-mounted and liquid cooled. The coolant is pink, which makes it identifiable on a wet floor pan, and BYD’s wording on the rescue sheets is unambiguous:

When there is coolant leakage, the battery pack may become unstable and there is risk of thermal runaway. The battery pack temperature must be checked with a thermal imaging camera.

Read that as an equipment requirement, not advice. On a car that has been hit underneath, pink coolant under the floor pan moves the job from inspect and quote to measure the pack temperature before anything else. Never breach the battery when lifting the vehicle, and never let a rescue tool or a jack stand pass through the floor pan.

What BYD Says About Fighting the Fire

The instruction is water, and a lot of it:

• Use water to fight a high-voltage battery fire. If the battery is on fire, exposed to high heat, or is generating heat or gases, cool it with large amounts of water. Because of the volume required, establish or request additional water supply early — do not wait until the first line runs dry.
• Apply water directly to the battery. If safety permits, lift or tilt the vehicle for more direct access. Apply water from a safe distance only if a natural opening already exists — a vent, or an opening created by the collision.
• Keep going until the pack is at ambient temperature. Use a thermal imaging camera (TIC or IR) to monitor throughout, and continue water until the indicated battery temperature is equal to or below ambient. When you stop, allow time for heat inside the pack to transfer to the enclosure before trusting the reading.
• Small fires that do not involve the high-voltage battery are handled with normal vehicle firefighting procedure — CO2, dry powder, or another standard agent.
• Use insulated tools and never make contact with high-voltage components while fighting the fire.

And then the part that matters more than any of the above — the four things BYD explicitly rules out:

1. Do not open the battery to cool it.
2. Do not submerge the vehicle to extinguish or cool a battery fire.
3. BYD does not recommend placing the vehicle in a large container full of water.
4. BYD does not recommend the use of foam on electric vehicles.

There is a fifth hazard running underneath all of it. Heat and flame compromise airbag inflators, the gas cylinders inside stored-gas inflators, and pressurised gas struts. Any of those can overheat and then explode with no further warning, which is why the guide insists on an adequate knock-down before anyone enters the hot zone.

The Numbers That Govern the Scene

Three figures do most of the work in real incident planning, and all three are BYD’s own:

Figure	What it means
Up to 24 hours	How long a battery fire may take to fully cool. Plan for a long scene, not a short one.
At least 45 minutes	Continuous period with no fire, no smoke, no audible popping or hissing, and no heating in the high-voltage battery before the vehicle can be released to second responders.
At least 50 ft (15 m)	Minimum distance from any other object for storing a vehicle that has been submerged, burned, or in a collision that compromised the pack — because of battery re-ignition risk.

Two further instructions come with those numbers. Second responders must be told about the re-ignition risk explicitly, and they should be advised to tilt or reposition the vehicle so excess water drains — that single action measurably reduces the chance of re-ignition. The battery must be completely cooled before the vehicle is released or moved off site.

What Comes Off a Burning Pack

A burning battery releases super-heated gases and toxic vapours. BYD’s own list of what may be in that plume is specific, and it is not a short list: volatile organic compounds, hydrogen gas, carbon dioxide, carbon monoxide, soot, and particulates carrying oxides of nickel, aluminium, lithium, copper and cobalt — plus hydrogen fluoride.

The practical consequences are short. Full PPE including self-contained breathing apparatus, every time, with no exceptions for a car that looks like it is only smouldering. And anyone downwind of the incident needs to be moved or protected. Nothing about the vehicle looks unusual in the first minute; by the time it is obvious, the plume is already there.

A damaged pack can heat its cells rapidly. If you see smoke or steam, or hear popping or hissing from the high-voltage battery, assume it is heating and act on that assumption immediately.

Flood-Damaged and Submerged Cars

This is the case most likely to walk into a workshop in a wet season. BYD’s position is measured but specific:

• The vehicle body does not present a greater risk of electric shock because it is in water. That is the reassuring half.
• Vehicles that have been submerged should be handled with greater caution due to the potential risk of a high-voltage battery fire, and responders should be prepared for it. That is the half people skip.
• Remove the vehicle from the water, then raise the front of the vehicle so water drains out of the vehicle and out of the high-voltage battery pack.
• Then continue with normal high-voltage disabling. If you have not got that procedure to hand, use the BYD high voltage shutdown procedure before doing anything else on the car.

Note the direction: raise the front, not the rear. Water trapped in the pack is the part that matters, and the pack is fed from the front of the floor pan.

Moving and Storing a Damaged Car

Transport is where damage usually gets worse, and BYD is unusually direct about it. These cars are front-drive, so during transport the front wheels must be off the ground and unable to spin. A flatbed with all four wheels off the ground is the recommendation.

• Towing on the front or rear wheels alone may damage high-voltage components.
• Never transport the vehicle with the tyres able to spin. Doing so can cause overheating and, in rare cases, set surrounding components alight.
• Never tow with ropes or chains — a proper flatbed or a professional recovery service only.
• Before transport, assume the high-voltage components are energised, even on a car that has already had airbags deploy, until someone qualified has confirmed otherwise.
• Store at a safe distance from other vehicles. The 15 m figure above is the working number.

The towing hook on the Sealion 5 lives behind a plug on the right-hand side of the front grille — your car may differ, so check the handbook for the exact model rather than assuming. The free official BYD handbooks cover the location for each model.

Two Timing Numbers to Carry Into Any BYD Job

Both come straight out of the same guide, and both are worth memorising because they bound what you can safely do and when:

• The high-voltage system is de-energised approximately 60 seconds after deactivation. Not instantly. The interval is the point.
• The RCM carries a backup power supply with a discharge time of approximately 10 seconds. Do not touch the RCM within 10 seconds.

After airbags deploy, the vehicle is in an abnormal state and you are told to leave it immediately — the automatic high-voltage deactivation that follows is a mechanism, not a licence to start working.

Where a Workshop’s Scope Actually Ends

The useful thing about reading the manufacturer’s own emergency document is that it draws the boundary for you, in the manufacturer’s own words:

• In scope: diagnosis, mechanical work, high-voltage shutdown by the published procedure, waiting the 60 seconds, identifying a damaged pack by the coolant trail, and owning a thermal imaging camera.
• At the edge: anything requiring the vehicle to be lifted or manipulated around the pack area — only with training and with the assumption that everything is live.
• Out of scope: opening a pack. BYD does not even permit it for cooling during an active fire, and its language around breaches is fatal-injury language.

In practice, the highest-value habit is the cheapest one: park a suspected damaged or flooded car away from the building and from other vehicles, check the pack temperature with a thermal camera before it comes in, and treat smoke, steam, popping or hissing as an evacuation trigger rather than a diagnostic clue. None of that requires a high-voltage qualified technician. It requires knowing what the manufacturer wrote down.

Source

Compiled from the official BYD Sealion 5 Emergency Response Guide (English edition) — stored energy, fire response, submersion, towing and storage, and additional safety information — with pack voltages and low-voltage battery ratings cross-checked against the BYD Seal, Seal 6, Shark 6, Atto 2 and Sealion 7 rescue sheets. Figures are quoted as published by the manufacturer for the Australian-market models shown in those documents. Always confirm against the guide for the exact model and variant in front of you.