Why do Electric Bicycles Catch Fire?

Recently, there have been increasing incidents of electric bicycle fires in the United States, which have sparked discussions and panic regarding battery safety issues. So, are electric bicycles really prone to catching fire and exploding? Next, we will analyze in depth the reasons behind electric bicycle fires.


Before answering this question, let's briefly explain some common knowledge about electric bicycle batteries. Electric bicycles commonly use lithium-ion batteries, which have the advantage of high energy density but the disadvantage of high reactivity and lower safety. However, current electric cars also widely use lithium-ion batteries, yet the frequency and probability of car fires are very low, thanks to the high quality requirements imposed by car manufacturers on lithium batteries. This indicates that by improving battery management quality, the battery safety issues of electric bicycles may be resolved.


The main reasons for electric bicycle fires are as follows:


Unqualified recycled battery overheats causing fire

The primary reason is the use of unqualified recycled batteries. Batteries have a lifespan, and lithium-ion batteries typically have a usage cycle of around 500 charges, lasting approximately 3 to 5 years. Recycled batteries are mainly sourced from scrapped car batteries or improperly used substandard battery cells in the production of electric bicycle batteries. Why would electric bicycle manufacturers choose recycled battery cells? The cost of batteries accounts for over 30% of the entire product, while recycled batteries cost less than half of high-quality batteries. Therefore, a large number of recycled batteries are used in low-end electric bicycles.

The production requirement for manufacturing lithium-ion batteries is to connect battery cells with similar resistance values to form a battery pack. Since recycled batteries have significantly different resistance values, the batteries produced are inevitably substandard. Most electric bicycle fires occur during the charging process. When charging, battery cells with lower resistance values have higher lithium ion activity, leading to battery overheating and causing fires.


Traffic accident cause battery exposed and damaged

Another major cause of electric bicycle fires is traffic accidents. When lithium-ion batteries are impacted, squeezed, or punctured during an accident, they can immediately ignite, resulting in a fire throughout the vehicle's circuitry. Due to the unreasonable design of low-end bicycle structures, the batteries are often externally attached to the frame, making them prone to collision damage in accidents. Even without accidents, batteries exposed to long-term exposure to wind and sun can accelerate aging, thereby posing safety hazards. Currently, a more reasonable product design involves concealing the battery inside the frame. Since the frame walls are relatively thick, even in the event of an accident, the battery is not easily exposed and damaged. Additionally, this design approach provides better protection against accelerated battery aging caused by natural conditions.

Other factors such as quality issues with the Battery Management System (BMS), motor, controller, and other malfunctions can also lead to battery overheating and fires. However, the probability of such accidents occurring is relatively low. Nowadays, when consumers purchase electric bicycles, they mostly focus on the battery capacity but overlook the brand quality of the battery cells. Internationally, well-known brands for electric bicycle battery cells include Panasonic, Samsung, LG, and others, which are all excellent choices. Since the quality of batteries cannot be judged solely by appearance, professional testing equipment is required to evaluate them. If users are concerned about the safety of electric bicycles, they can have them tested by relevant inspection agencies before use to avoid accidents.