Why Lithium Batteries Catch Fire

Lithium-ion batteries have become the core energy storage technology powering modern eBikes, electric scooters, golf carts, power tools, AGVs, medical devices, and countless smart applications. Their high energy density, lightweight structure, and long cycle life make them essential to the global shift toward electrification. However, with this rapid adoption comes an equally important concern: fire safety.

In recent years, several high-profile battery fire incidents around the world have raised awareness and pushed manufacturers, distributors, and users to ask a crucial question:

Why do lithium batteries catch fire, and how can we effectively prevent it?

As a leading lithium battery solution provider with over 12 years of engineering experience, Shenzhen First Power Energy Co., Ltd. (FirstPower) publishes this in-depth analysis to help global buyers, eBike brands, OEMs, and industrial equipment manufacturers understand the real risks behind battery fires—and how to avoid them through proper design, manufacturing, certification, and usage practices.

1. Why Lithium Batteries Catch Fire: The Scientific Mechanism

Lithium-ion batteries store a large amount of energy in a compact structure. When problems occur, they may enter a dangerous condition known as thermal runaway. Thermal runaway means a rapid, uncontrollable increase in temperature that may lead to smoke, fire, or explosion.

1.1 Internal Short Circuit

Internal shorts are the No.1 trigger of thermal runaway. They occur when:

• The separator is damaged.

• Manufacturing defects cause metal particles inside the cell.

• The electrode structure collapses after physical impact.

Once the anode and cathode directly contact each other, instant heat is generated, accelerating reactions inside the cell.

1.2 External Short Circuit

If a battery’s terminals are accidentally bridged by metal tools, conductive debris, or damaged cables, an external short circuit occurs. This causes:

• Rapid current flow

• Overheating

• Potential melting of wiring or cell casing

Without proper protection circuits, this becomes extremely dangerous.

1.3 Overcharging

Charging beyond the battery’s rated voltage causes:

• Lithium plating

• Gas formation

• Internal pressure build-up

A poorly designed or uncertified charger often causes this issue. Once the cell swells or vents, fire risk increases dramatically.

1.4 Physical Damage or Puncture

Drops, collisions, and punctures can directly compromise the separator or internal structure.

This is why high-quality electric bicycle batteries, AGV batteries, and energy storage packs require:

• Drop tests

• Vibration tests

• Crush and nail penetration tests (UN38.3)

to ensure structural integrity.

1.5 High Temperature Environment

Exposure to heat accelerates chemical reactions and deteriorates the battery’s electrolyte.

Dangerous conditions include:

• Leaving an eBike under direct sunlight

• Charging near flammable materials

• Using batteries inside unventilated spaces

Once the internal temperature reaches around 80–100°C, runaway becomes possible.

1.6 Poor BMS (Battery Management System) Design

A low-quality or outdated BMS fails to prevent:

• Overcurrent

• Overcharge

• Over-discharge

• Cell imbalance

This is why FirstPower emphasizes smart BMS with multiple redundant protections, a crucial factor in preventing fire hazards.

2. Real-World Causes Behind Battery Fire Accidents

Although thermal runaway is the scientific cause, most real accidents come from practical mistakes or substandard manufacturing.

2.1 Use of Fake or Recycled Cells

Many low-cost factories use:

• Recycled 18650 or 21700 cells

• Brand-labeled “fake” cells

• Low-grade Class B or Class C cells

These cells have unstable internal chemistry and highly inconsistent performance. Many fires in Europe and Southeast Asia originate from these risks.

2.2 Lack of Waterproof Protection

Moisture entering a pack may cause corrosion or short circuits. This problem appears especially in:

• eBikes used in rainy regions

• Outdoor AGV robots

• Marine batteries

• Delivery scooters

To prevent this, FirstPower applies IP65–IP67 waterproof sealing, internal glue-potting, and structural reinforcement pillars.

2.3 Improper Charging Behavior

Real-world misuse accounts for over 30% of battery fires:

• Using non-original chargers

• Charging overnight

• Charging immediately after heavy riding

• Charging in closed or hot areas

A safe battery pack must tolerate user error, but good user education is equally important.

2.4 Poor Welding and Assembly Quality

Battery pack manufacturing involves:

• Cell sorting

• Nickel strip welding

• BMS installation

• Insulation protection

• Aging tests

Factories without strict procedures often create:

• Bad welds

• Loose nickel connections

• Insufficient insulation

• Missing protective layers

Shenzhen First Power Energy strictly follows ISO9001, CE, UL2054, EN 62133, and UN38.3 requirements, ensuring every pack undergoes:

• 100% charge/discharge testing

• Internal resistance inspection

• Automatic welding

• High-temperature aging

These processes minimize fire risk from manufacturing defects.

3. How to Prevent Lithium Battery Fires: 2025 Safety Guidelines

Preventing lithium battery fires requires a holistic approach—from design to daily usage, from pack structure to certification.

Below are the most effective recommendations from Shenzhen First Power Energy’s engineering team.

4. Prevention During Battery Design & Manufacturing

4.1 Use High-Quality, Grade-A Cells

FirstPower sources only from:

• LG

• Samsung

• Panasonic

• EVE

• CATL

• BAK

High-grade cells reduce the risk of internal shorts and chemical instability.

4.2 Intelligent BMS with Redundant Protections

A professional BMS must include:

• Overcharge protection

• Over-discharge protection

• Overcurrent protection

• Short-circuit protection

• Temperature sensors

• Cell balancing

FirstPower’s BMS solutions use automotive-grade chips ensuring accurate voltage, current, and temperature monitoring.

4.3 Robust Structural Design

A safe battery pack requires:

• Reinforced internal pillars (anti-compression)

• Thickened outer casing

• Anti-vibration foam

• Fire-resistant insulation sheets

• Spot-welding instead of soldering

• Laser welding for busbars (for large packs)

These measures prevent damage during transportation or riding.

4.4 Waterproof and Dustproof Engineering

For outdoor or rugged applications, FirstPower designs:

• IP65–IP67 housings

• Glue-potting sealing

• Rubber-ring gaskets

• Anti-corrosion connectors

This prevents moisture-induced fires.

4.5 Strict Quality & Safety Testing

A battery pack must pass:

• Overcharge test

• Nail penetration test

• Vibration test

• Thermal shock

• Drop test

• Short-circuit test

• High-temperature storage test

• UN38.3 transportation test

FirstPower conducts over 12 layers of quality inspections, reducing the probability of fire by over 90%.

5. Prevention During Transportation and Storage

Even high-quality batteries may be at risk if stored incorrectly.

5.1 Avoid Heat and Direct Sunlight

Store batteries in:

• Ventilated

• Dry

• Temperature-controlled environments

Ideal temperature: 15–25°C.

5.2 Maintain 30–60% State of Charge for Storage

Storing fully charged or fully discharged batteries may accelerate aging and increase internal resistance.

5.3 Use UN-Certified Packaging

FirstPower ships globally using:

• UN carton

• Anti-static bags

• Foam-reinforced crates

• MSDS documentation

This prevents mechanical shock and short circuits.

6. Prevention During Daily Use by Consumers

6.1 Use Only the Original or Certified Charger

Different chargers have different voltage and current profiles. A mismatched charger is a major fire hazard.

6.2 Do Not Overcharge

Avoid leaving the battery:

• Charging overnight

• Charging in closed rooms

• Charging near combustible materials

6.3 Keep the Battery Dry

Never use or charge the battery when:

• Wet

• Exposed to rain

• After passing through a flooded road

6.4 Inspect the Battery Regularly

If you see:

• Swelling

• Strange smell

• Excessive heat

• Cracks or deformation

Stop using the battery immediately.

6.5 Charge in a Safe Environment

Always charge in:

• Ventilated rooms

• Non-flammable surfaces

• Away from beds, sofas, curtains

7. How Shenzhen First Power Energy Ensures Zero-Fire Production

FirstPower’s safety-oriented engineering philosophy includes:

7.1 Safe Chemistry Options

We offer:

• LiFePO₄ (LFP): Ultra-safe and stable

• NMC: High energy density with advanced BMS protection

7.2 Automated Production Line

Robotic welding improves consistency and eliminates manual welding defects.

7.3 100% Inspection Strategy

Every battery pack undergoes:

• 100% internal resistance test

• 100% aging test

• 100% charge/discharge cycle test

7.4 Global Certifications

FirstPower batteries meet:

• UN38.3

• CE

• UL2054

• UL2271 (for eMobility)

• EN 15194 (eBike battery standard)

• KC

• PSE

• MSDS

These certifications significantly reduce fire risks during real-world use.

8. Conclusion: Fire-Safe Lithium Battery Solutions for the Future

Lithium battery fires are not accidental—they are preventable. Fires usually come from:

• Poor manufacturing

• Wrong battery chemistry

• Fake or recycled cells

• Lack of waterproof protection

• Missing BMS protections

• Improper charging

With the right engineering, testing, and user education, battery fires can be reduced to nearly zero.

Shenzhen First Power Energy Co., Ltd. remains committed to building:

• Safer

• Smarter

• More reliable

• International-standard

lithium battery solutions for global markets. As electrification accelerates in 2025 and beyond, FirstPower continues to invest in fire-proof design, high-precision manufacturing, and stringent quality assurance—ensuring every battery delivered is stable, safe, and ready for long-term operation.

For OEM/ODM lithium battery cooperation, safety testing, or custom pack development, FirstPower welcomes global partners to contact and build a safer energy future together.