What kind of “core” is installed in such a “bad-tempered” electric bicycle?

Audit expert: Luo Huachun

Editor-in-Chief of Cities and Disaster Reduction

In Beijing, where traffic congestion is getting worse, no matter how fast a car runs, it may not be as fast as an electric bicycle, so electric bicycles have become the first choice for many friends to travel.

Source: Tencent News

With the increasing popularity of electric bicycles, the potential safety hazards of electric bicycles have also become a hot topic of concern. Although the use of electric bicycles has become more and more standardized with the release of the "New National Standard" and the implementation of the electric bicycle registration system, the continuous increase in the number of electric bicycles and the occurrence of explosion accidents have made electric bicycles the protagonist of many accidents.

According to statistics from the National Fire and Rescue Bureau, a total of 21,000 electric bicycle fires were reported nationwide in 2023, up 17.4% from 2022. Why are electric bicycles so "flammable and explosive"? Let's start with its "core".

The explosive core: lithium battery

On April 15, 2019, my country officially implemented the "Electric Bicycle Safety Technical Specifications", which we often call the "New National Standard", which clearly stipulates a series of parameters for electric bicycles:

1. The vehicle speed should not exceed 25KM/h

2. The vehicle mass does not exceed 55KG

3. The battery voltage does not exceed 48V

4. The rated continuous output power of the motor shall not exceed 400W

5. It has pedals and can be ridden

6. The power is electric drive or electric power assist

According to the relevant provisions of the "New National Standard", lithium batteries have become the most suitable battery "core" for electric bicycles due to their advantages of lighter weight, higher energy density and longer life .

The lithium battery we are talking about now is the lithium-ion battery, which uses a lithium-containing metal compound as the positive electrode material, graphite as the negative electrode material, and a non-aqueous electrolyte solution. This is a reusable battery (rechargeable battery) widely used in mobile phones, laptops, electric bicycles, and electric vehicles.

Source: NetEase News

Lithium batteries are still active in all aspects of life, but they are not a good "emotionally stable" partner. If we cannot treat them scientifically, we will become victims of their "flammable and explosive" nature.

Why are lithium batteries “flammable and explosive”?

Lithium batteries have many advantages, but they have one biggest disadvantage, which is "emotional instability". The cause of this "character flaw" is "lithium dendrites".

Lithium is a very active metal, so active that it can set anyone on fire. Although developers have been improving the safety of lithium batteries in various ways, short circuits between positive and negative electrodes, overcharging, overdischarging, and high temperatures may still cause lithium ions to go from a stable state to an "excited" state again.

Source: Sohu

During the repeated charge and discharge process of lithium batteries, metallic lithium will inevitably precipitate. These precipitated lithium will gradually deposit to form lithium dendrites. When reaching a certain level, they will penetrate the diaphragm, causing a short circuit inside the battery, causing the temperature and pressure of the lithium battery to continue to rise, and eventually an explosion will occur.

How to deal with the "violent temper" of lithium batteries?

Lithium batteries have a bad temper, but if we use them scientifically and rationally, we can still live in harmony with them.

The first thing to do is to charge the vehicle when there is someone supervising it during the day. Do not place the charged electric vehicle in corridors or escape passages. Do not modify or purchase unqualified electric bicycles at will. Daily inspections should also be strengthened.

Source: Science Popularization China

So if the lithium battery starts to get "angry", how can we make it "calm down" sooner?

1. Cut off the power supply

2. Block flammable materials

3. Sprinkle water on the device

4. Do not attempt to remove, pick up or move the device.

As the demand for electric bicycles for commuting increases, its safety issues have also attracted widespread attention. There have been proposals to revise the "new national standard", such as increasing the maximum weight of electric bicycles, ensuring battery capacity, and adding safety technology.

It is reported that the University of Science and Technology of China and Jinan University have developed a high-precision fiber optic sensor that can be implanted inside the battery, which can monitor the battery status in real time and avoid safety hazards such as explosions. The advancement of technology has made lithium-ion batteries more and more "tempered", and our travel safety has also been better guaranteed.

Are you an electric bicycle rider?

Don’t forget to take good care of that “bad-tempered” friend in your car!