So Many Batteries!  18650 primer

So Many Batteries! 18650 primer

It is starting to become impossible to avoid. Battery technology is everywhere now and it’s time to get a refresher on the technologies available and cover some issues with the use and safety.

Batteries are integral to our daily routines, powering a wide range of devices from the mundane to the high-tech. Imagine a day without your smartphone, laptop, or even your electric vehicle – life would come to a standstill. There are many types of batteries, each serving different purposes, but today we focus on a particular kind: the 18650 battery. What do you know about how these batteries are made and what ensures their safety?

lithium-ion VS Lithium-Polymer (LiPo) battery

The 18650 battery is not a Lithium-Polymer (LiPo) battery; rather, it is a specific type of lithium-ion battery. The designation “18650” refers to the battery’s size and shape, with dimensions of 18mm in diameter and 65mm in length. These batteries are commonly used in a wide range of electronic devices, including laptops, flashlights, power tools, and electric vehicles.

Just to cover the Two types of battery technology we encounter

While both Lithium-Polymer (LiPo) and Lithium-Ion (including 18650) batteries fall under the broader category of lithium-based rechargeable batteries, they have distinct differences in terms of chemistry, design, and characteristics:

  • Lithium-Ion (18650) Batteries:
    • Chemistry: Typically use a lithium-cobalt oxide cathode and graphite anode.
    • Design: Cylindrical shape (18650) with a metal casing.
    • Characteristics: Known for high energy density, good performance, and moderate safety risks if mishandled.
  • Lithium-Polymer (LiPo) Batteries:
    • Chemistry: Utilize a polymer electrolyte instead of a liquid electrolyte.
    • Design: Flexible pouch or prismatic cell design.
    • Characteristics: Offer higher energy density, lighter weight, and greater design flexibility but can be more prone to thermal runaway and fire incidents if improperly handled.

More on the Common 18650 – Materials

Materials Used in 18650 Batteries

The performance and safety of 18650 batteries are largely determined by the materials used in their construction. Here are the primary components:

  1. Cathode Materials:
    • Lithium Cobalt Oxide (LiCoO2): High energy density, suitable for high-performance applications.
    • Lithium Manganese Oxide (LiMn2O4): Balanced energy density and safety, ideal for safe applications.
    • Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2): High energy density and stability, perfect for electric vehicles.
  2. Anode Materials:
    • Graphite: Common choice due to good cycling stability and conductivity.
    • Lithium Titanate (Li4Ti5O12): Excellent safety and long cycle life but lower energy density.
    • Silicon: High energy density but faces volume expansion challenges during charging.
  3. Electrolyte:
    • Typically Lithium hexafluorophosphate (LiPF6) in solvents like ethylene carbonate or dimethyl carbonate, affecting conductivity, safety, and temperature range.
  4. Separator:
    • Polyethylene or Polypropylene: Impacts internal resistance, safety, and cycle life.
  5. Binder:
    • Polyvinylidene fluoride (PVDF): Ensures mechanical stability and cycling performance.

By carefully selecting and optimizing these materials, manufacturers can tailor the 18650 battery’s performance to meet specific application requirements.

Quality Standards for 18650 Batteries

Quality standards are critical in ensuring the reliability and safety of 18650 batteries. These standards govern everything from material selection to manufacturing processes and final product testing. High-quality batteries are subject to rigorous testing to ensure they meet performance criteria and safety regulations, such as:

  • UN38.3 Certification: Ensures safe transportation of lithium batteries.
  • IEC 62133 Certification: Specifies safety requirements for portable sealed secondary cells and batteries.

Manufacturing Process of 18650 Batteries

The manufacturing process of 18650 batteries involves several steps, each crucial for ensuring the battery’s performance and safety:

  1. Material Preparation: High-purity raw materials are prepared and mixed.
  2. Electrode Production: The cathode and anode materials are coated onto metal foils.
  3. Cell Assembly: The electrodes, separator, and electrolyte are assembled into a cell casing.
  4. Formation and Aging: The assembled cells are charged and discharged to form a stable structure and tested for performance.
  5. Quality Control: Final products undergo stringent testing to ensure they meet quality and safety standards.

Safety Considerations and Proper Storage of 18650 Batteries

Safety is paramount when dealing with 18650 batteries, given their high energy density. Here are key safety considerations:

  • Battery Management Systems (BMS): Monitor and manage the battery’s performance, preventing overcharging, over-discharging, and overheating.
  • Thermal Management: Systems to regulate and dissipate heat.
  • Cell Design: Features like shutdown separators and venting mechanisms to prevent thermal runaway.
  • Quality Control: Ensures consistent and reliable battery performance.

Proper Storage of 18650 Batteries

Proper storage is essential to maintain the performance, safety, and longevity of 18650 batteries:

  1. Temperature: Store in a cool, dry place away from direct sunlight and extreme temperatures.
  2. Avoid Moisture: Prevent damage from moisture or water.
  3. Avoid Physical Damage: Store securely to avoid impact or crushing.
  4. Charge Level: Store at a partial charge (40-60%) for extended periods.
  5. Isolation: Use non-conductive containers to prevent short circuits.
  6. Ventilation: Ensure proper ventilation to prevent gas accumulation.
  7. Labeling: Clearly label batteries with their chemistry, voltage, and handling instructions.
  8. Keep Away from Children and Pets: Store in a location inaccessible to children and pets.
  9. Regular Inspection: Periodically check for signs of damage, leakage, or swelling.

By adhering to these best practices, users can ensure their 18650 batteries remain safe and functional over their lifespan.

How to store 18650 battery for long storage

Storing 18650 batteries properly is crucial to maintain their performance, safety, and longevity. Here are detailed guidelines on how to store 18650 batteries for long-term storage:

1. Charge Level

  • Optimal Storage Charge: Store batteries at around 40-60% charge. Storing them fully charged or completely drained can reduce their lifespan. A partial charge helps maintain the battery’s health over time.

2. Temperature

  • Cool Environment: Store batteries in a cool place, ideally between 0-25 degrees Celsius (32-77 degrees Fahrenheit). Avoid storing batteries in areas with high temperatures, such as near heaters or direct sunlight, as heat can accelerate battery degradation.
  • Avoid Freezing: While cool temperatures are beneficial, extremely cold environments can also be harmful. Ensure the storage area is above freezing point.

3. Humidity

  • Dry Location: Keep batteries in a dry place to prevent moisture from causing corrosion or short circuits. Moist environments can lead to internal damage and decrease battery life.

4. Physical Protection

  • Non-Conductive Containers: Store batteries in non-conductive, non-metallic containers to prevent accidental short circuits. Battery cases or specially designed storage boxes are ideal.
  • Avoid Physical Damage: Ensure batteries are protected from physical damage. Do not store them in a place where they can be crushed, dropped, or impacted.

5. Isolation

  • Separate from Metal Objects: Do not store batteries loose where they can come into contact with metal objects, which can cause short circuits. Use individual battery cases if possible.

6. Ventilation

  • Adequate Airflow: Ensure the storage area is well-ventilated. Proper airflow helps dissipate any heat generated and prevents the build-up of gases in case of a battery malfunction.

7. Regular Inspection

  • Periodic Checks: Regularly inspect stored batteries for any signs of damage, leakage, or swelling. If any abnormalities are detected, properly dispose of the affected batteries according to local regulations.

8. Labeling

  • Clear Identification: Clearly label stored batteries with important information such as charge level, date of storage, and any special handling instructions. This helps in maintaining proper usage and storage routines.

9. Safety Precautions

  • Keep Away from Children and Pets: Store batteries in a location that is inaccessible to children and pets to prevent accidental ingestion or mishandling.
  • Emergency Plan: Have a plan in place for dealing with potential battery leaks or fires. Store batteries in a place where fire extinguishers or other safety equipment are easily accessible.

10. Environment Considerations

  • Away from Flammable Materials: Store batteries away from flammable substances or chemicals to reduce fire hazards.

By following these guidelines, you can ensure that your 18650 batteries remain in good condition during long-term storage, ready to deliver optimal performance when needed.

what happens if a 18650 battery is put into a fire?

If a 18650 battery is put into a fire, several dangerous and potentially catastrophic events can occur due to the nature of lithium-ion batteries. Here’s a detailed explanation of what happens and why it is extremely hazardous:

1. Thermal Runaway

  • Heat Exposure: When a 18650 battery is exposed to high temperatures, such as those in a fire, the heat can cause the electrolyte inside the battery to heat up and expand.
  • Exothermic Reaction: This can lead to an exothermic reaction, known as thermal runaway, where the battery’s internal temperature increases rapidly and uncontrollably.

2. Pressure Build-Up

  • Gas Generation: The high temperatures can cause the electrolyte to decompose and produce gases. This gas generation leads to a significant build-up of pressure inside the battery.
  • Rupture: If the pressure becomes too great, it can cause the battery casing to rupture explosively.

3. Fire and Explosion

  • Combustible Materials: Lithium-ion batteries contain flammable materials, including the electrolyte and sometimes the cathode materials.
  • Ignition: The high temperatures can ignite these materials, resulting in a fire. The gases produced under pressure can also be highly flammable, leading to an explosion.
  • Shrapnel: The explosion can scatter shrapnel and hot, burning materials over a wide area, posing a serious risk to anyone nearby.

4. Release of Toxic Fumes

  • Harmful Chemicals: Burning lithium-ion batteries can release toxic fumes, including hydrogen fluoride, carbon monoxide, and other hazardous compounds.
  • Inhalation Risk: These fumes are dangerous if inhaled and can cause respiratory issues, chemical burns, and other health problems.

5. Environmental Impact

  • Contamination: The release of chemicals can also contaminate the environment, affecting air quality and potentially polluting water and soil.

Safety Considerations

Given the severe risks associated with lithium-ion batteries, it is crucial to handle them with care:

  • Avoid Fire Exposure: Never intentionally expose 18650 batteries to fire or high temperatures.
  • Proper Disposal: Dispose of damaged or old batteries at designated recycling centers or hazardous waste facilities.
  • Emergency Procedures: In case of a fire involving lithium-ion batteries, use a Class D fire extinguisher designed for metal fires. Water or regular fire extinguishers may not be effective and can sometimes exacerbate the situation.

If it won’t charge because you let it go to zero voltage

Reviving a zero-volt Lithium-Polymer (LiPo) battery, also known as a deeply discharged battery, can be a delicate process that requires caution to avoid further damage or safety risks. Here is a general guide on how to attempt to revive a zero-volt LiPo battery:
(if you explore dead lipo battery you will encounter a method to fix this and it’s easy but not the recommended method, but it works) connect a charged lipo to the dead one positive to positive and negative to negative for 1 minute, this will equalize the dead battery voltage and allow it to show up on your charger to be charged.

Materials Needed:

  • LiPo Battery Charger: A specialized LiPo battery charger capable of handling deeply discharged batteries.
  • Power Supply: A power source with adjustable voltage and current settings.
  • Safety Gear: Safety goggles, gloves, and a fireproof charging bag or container.

Reviving Process:

  1. Safety Precautions:
    • Ensure you are working in a well-ventilated area away from flammable materials.
    • Wear safety goggles and gloves to protect against any potential battery leakage or fumes.
    • Have a fireproof charging bag or container ready in case of any unexpected reactions.
  2. Check Voltage:
    • Use a multimeter to check the voltage of the zero-volt LiPo battery. If it reads zero volts, proceed with caution.
  3. Pre-Charge Preparation:
    • Set your power supply to a very low voltage (e.g., 1-3V) and current limit (e.g., 0.1-0.5A).
    • Connect the LiPo battery to the power supply using the correct polarity (red to positive, black to negative).
  4. Gradual Recharge:
    • Slowly increase the voltage on the power supply in small increments while monitoring the battery voltage.
    • If the battery voltage starts to rise, continue the charging process at a very low rate.
    • Do not leave the battery unattended during the charging process.
  5. Monitoring and Testing:
    • Periodically check the battery temperature during charging. If it becomes hot to the touch, stop charging immediately.
    • After a while, check if the battery voltage has reached a safe level for regular charging (usually above 3V per cell).
  6. Regular Charging:
    • Once the battery voltage has increased to a safe level, use a specialized LiPo battery charger to fully charge the battery following standard charging procedures.
  7. Testing and Usage:
    • After charging, test the battery’s performance and capacity to ensure it has been successfully revived.
    • Monitor the battery during subsequent uses to ensure it remains stable and does not exhibit any abnormal behavior.


  • Reviving a zero-volt LiPo battery is a risky process and may not always be successful. If the battery shows signs of swelling, extreme heat, leakage, or other abnormalities during the charging process, stop immediately and dispose of the battery safely.
  • It is always recommended to handle LiPo batteries with care and follow proper charging, usage, and storage guidelines to prevent deep discharge situations in the future.

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