Battery fires in e-bikes and electric scooters are rare but can be serious. Understanding the main causes helps us prevent them and ride safely. Here are the top five reasons why these fires happen, from most to least common—and tips to prevent them.
1. Fast Charging
Many of us are used to filling up our cars in a matter of minutes, but with e-bikes and electric scooters, that mindset can lead to trouble. These batteries are more like phone batteries than petrol tanks: they’re designed to charge gradually for optimal performance. Using aftermarket fast chargers can push the battery’s limits, overwhelming internal cells and leading to “thermal runaway”—a rapid, uncontrollable rise in temperature.
Put simply, each battery cell has its own internal resistance, which generates a normal amount of heat during charging. But if the charging rate is too high, it creates excess friction and heat, which can ignite the battery. Aftermarket fast chargers are therefore a top cause of battery fires. Most manufacturers design their batteries with tolerances that can handle a slightly faster charge, but for anything beyond that, it’s best to consult your battery supplier.
2. Poor Manufacturing and Lack of Maintenance
On par with fast charging, the combination of poor battery manufacturing and a lack of maintenance also plays a major role in battery fires. Battery packs for e-bikes and scooters are built by connecting many smaller cells (similar to AA batteries) into a single, high-power source. To function safely, each of these cells needs to have nearly identical internal resistance. Reputable manufacturers use machines to check and match each cell’s resistance before assembly, but some cut costs by skipping these quality checks.
If the cells’ resistances don’t match, charging and discharging become uneven, and some cells may overheat. High-resistance cells heat up faster and charge slower, potentially causing neighbouring cells to overcharge, which can lead to fire. Poor-quality manufacturing, such as using substandard nickel strips to connect cells or poor orientation of battery packs, further increases the risk.
Lack of maintenance also contributes to battery issues. Over time, cells degrade naturally, and their resistance increases. This can happen faster if the battery is exposed to extreme temperatures or moisture, like leaving it in direct sunlight or using it in wet conditions without proper waterproofing. Regular maintenance catches early signs of wear or resistance issues, reducing the risk of problems down the road. At Electric Pedal Power, we recommend professional bi-annual check-ups for any battery over two years old to catch early warning signs before they escalate. Our advanced workshop equipment enables detailed load tests, cell balance checks, and thorough visual inspections, providing essential insights to extend your battery's lifespan. Contact us today for more information or to book your battery's health check-up.
3. Battery Management System (BMS) Failure
A Battery Management System (BMS) protects against overcharging and overheating by managing the battery's power. When a BMS fails, the battery can no longer control charging and discharging safely. Warning signs of a BMS failure include the inability to charge or power the device, sudden power cuts while riding, or the battery shutting off under load. While less common than issues like fast charging or poor manufacturing, BMS failures can lead to fires if charging continues unchecked. Attempting to bypass a faulty BMS or overcharge the battery in hopes of "reviving" it can create dangerous conditions. Fortunately, a failed BMS typically presents these warning signs before causing major issues, such as rendering the battery unusable. A failed BMS may also be mistaken for an unbalanced or aged battery, which can result from poor manufacturing or lack of maintenance (as discussed in item No. 2). If you suspect BMS issues, bring your battery to our workshop for a full check-up. Contact us for more information.
4. Using Aftermarket Accessories
Aftermarket controllers and motors are popular for enhancing e-bike and scooter speed and performance, but these upgrades can place excessive demands on the battery. Think of the battery as a large water tank and the controller as a tap that regulates the flow to the motor. If the tap is modified to release too much at once, it can strain both the motor and the battery, potentially overheating them.
While the BMS should cut off power before reaching dangerous levels, adding aftermarket parts can increase the risk of battery fires, especially if combined with other factors like poor manufacturing or lack of maintenance. At Electric Pedal Power, we love customisation, but the battery’s limits should always be respected. If you’re considering performance upgrades, talk to us first to ensure they’re compatible with your battery’s specifications.
5. Physical Damage and Environmental Stress
Physical damage, such as often dropping your e-bike or scooter, can disrupt the delicate cells inside the battery. Even small dents or shifts in the alignment of cells can increase the risk of short circuits, which can lead to overheating or battery failure. Additionally, exposing your battery to extreme temperatures—whether from direct sunlight, high heat, or damp conditions—can put undue stress on its internal chemistry, causing the cells to degrade faster and increasing the likelihood of thermal runaway in the long term.
To protect your battery, always handle your e-bike or electric scooter with care, and ensure it's stored in a shaded, dry, and well-ventilated area. If your battery has been exposed to high/continuous impacts or harsh environmental conditions, it's a good idea to have it inspected by a professional to identify any hidden damage and prevent further complications.
Conclusion
Taking good care of your e-bike or electric scooter battery is straightforward, and it helps ensure you get the most out of your ride. By avoiding fast charging, choosing quality batteries, and performing regular maintenance, you can keep your battery running smoothly for years.
At Electric Pedal Power, we’re here to support you with expert advice and professional services to keep your battery in top condition. Have any questions or want to book a battery check-up? Get in touch with us today. With just a little care, your e-bike or scooter will continue to deliver a safe, fun, and reliable riding experience for years to come!