Preventing thermal runaway in lithium-ion batteries

Preventing thermal runaway in lithium-ion batteries, particularly in high-performance ebikes, is essential for safety and longevity. Thermal runaway occurs when a battery cell's temperature rapidly increases, potentially causing a chain reaction that can lead to a fire or explosion. Here are several strategies to prevent thermal runaway:

1. Use High-Quality Cells

• Cell Selection: Opt for high-quality cells, such as Molicel P45B, which have a lower risk of defects and are known for better thermal stability.
• Matching Cells: Ensure all cells in a battery pack are well-matched in capacity and internal resistance to prevent uneven charging or discharging, which can cause overheating.

2. Implement Advanced Battery Management Systems (BMS)

• Temperature Monitoring: A good BMS constantly monitors the temperature of the cells and cuts off the power if the temperature exceeds a safe threshold.
• Overcharge and Overdischarge Protection: The BMS should protect against overcharging and over-discharging, which can cause excessive heat buildup.

3. Ensure Adequate Thermal Management

• Heat Dissipation Design: Use materials that efficiently dissipate heat, like PET-GCF and ASA, for battery enclosures.
• Cooling Solutions: Consider passive cooling solutions like heatsinks or thermal pads, or even active cooling methods like fans or liquid cooling for high-powered applications.

4. Limit Current Draw

• Controller Settings: Adjust the controller settings to prevent excessive current draw that could cause cells to overheat. High-performance ebikes should be configured to balance power and safety.
• Load Management: Avoid prolonged periods of maximum load, as this can cause the cells to heat up rapidly.

5. Use Protective Materials and Enclosures

• Epoxy Resin Coating: Applying an epoxy resin coating to the battery pack can help contain and slow down thermal propagation in the event of a single cell failure.
• Physical Barriers: Include materials that act as thermal barriers between cells to prevent a single cell's thermal runaway from affecting the others.

6. Avoid External Damage

• Proper Mounting: Ensure the battery is securely mounted to the bike to prevent physical damage from vibration or impact, which could lead to short circuits and thermal runaway.
• Protective Enclosures: Use robust enclosures that can withstand external shocks and protect the cells from punctures or crush injuries.

7. Regular Inspection and Maintenance

• Regular Check-Ups: Inspect battery packs regularly for signs of damage, swelling, or overheating. Remove any damaged cells promptly to prevent potential issues.
• Balanced Charging: Regularly balance charge the battery to ensure all cells are equally charged and avoid imbalances that can cause thermal runaway.

8. Proper Charging Practices

• Avoid Overcharging: Use chargers with built-in overcharge protection. Avoid leaving batteries charging unattended or overnight.
• Temperature Monitoring: Ensure batteries are charged within the recommended temperature range. Extreme temperatures can degrade battery cells and increase the risk of thermal runaway.

By following these strategies, you can significantly reduce the risk of thermal runaway and enhance the safety of your ebike conversion kits and battery packs. For customers looking to add additional protection to their batteries, consider offering them an epoxy resin coating service or encouraging them to use high-quality cells like Molicel P45B, known for their stability and reliability.