In recent years, electric bicycles have become more and more popular. Due to their simple operation and convenience, more and more people choose electric bicycles as a means of transportation for daily commuting. However, with the increase in the number, many electric bicycles that do not meet the quality standards are also sold on the market. In addition, some people use them improperly, and more and more fires caused by electric bicycles are also occurring.

Frequent charging of electric bicycles causes fires

In April this year, an electric bicycle shed on a university campus in Fujian suddenly caught fire in the early morning. Hundreds of bicycles and electric bicycles were burned, some of which were left with only skeletons. Many of the burned electric bicycles were still connected to the charger. The fire department initially determined that the fire was caused by the charging of electric bicycles. Fortunately, the fire did not cause any casualties.

Electric bicycles spontaneously combust and cause fire

However, a fire in Haikou City, Hainan Province in October 2015 was not so lucky. The fire caused 10 people to be sent to the hospital for treatment due to inhalation injuries, and 3 of them were seriously injured. The culprit of this fire was also an electric bicycle that was being charged. The surveillance camera in the building showed that on the afternoon of October 17, a woman parked an electric bicycle on the first floor to charge it. In the early morning of the 18th, the charging electric bicycle began to smoke and a flame jumped out within a dozen seconds. After burning the seat cushion, the fire quickly increased and spread to other electric bicycles in the surrounding area.

Surveillance records the spontaneous combustion of electric vehicles

Coincidentally, a fire also broke out in a residential building in Zhengzhou, Henan in 2014, and two residents who were riding in the elevator were trapped. The surveillance video showed that the electric bicycles stored on the first floor suddenly caught fire, and the fire burned bigger and bigger. After 2 minutes, the thick smoke quickly blocked the surveillance probe, and the fire was still spreading. At the moment the car door opened, the two were immediately surrounded by thick smoke, and the surveillance lost signal 3 minutes later...

During the investigation, the reporter learned that with the sharp increase in the number of electric bicycles, the number of fires caused by electric bicycles in China is also increasing. In 2011, 2012, and 2013 alone, fire departments across China counted 799 electric bicycle fires, killing 95 people and injuring 58.

Electric bicycle short circuits and open flames in two or three minutes

Firefighters once conducted a test on electric bicycle fire in an abandoned house. Let's take a look at the simulated scene.

Electric bicycle fire test

Only 2 minutes after the firefighters simulated an electric bicycle short circuit, the electric bicycle began to smoke. In the next minute, the open flame quickly spread to the body and battery pack of the electric bicycle. By 3 minutes and 30 seconds, both electric bicycles were on fire. At 5 minutes and 19 seconds, the whole building was covered with smoke.

The fire spread quickly

Only 8 minutes and 5 seconds after the short circuit, the electric bicycle parts began to explode. At this time, the firefighters who were measuring the temperature of the indoor smoke at the second-floor window could no longer hold on.

Test results are shocking: 90% of samples failed

According to relevant industries, the current social ownership of electric bicycles has exceeded 200 million, and the probability of electric bicycle fires is 2 in 100,000 per year. Some fire departments have made conservative calculations based on the probability of fire of 1 in 100,000, so there are at least 2,000 electric bicycle fires each year. It is worth noting that 75% of electric bicycle fires occur during charging. As an indispensable component of electric bicycles, the quality of chargers directly determines whether electric bicycles are safe. Not long ago, the Fujian Provincial Quality Inspection Institute conducted a risk test on electric bicycle chargers on the market, but the results were not optimistic.

90% of electric bicycle charger samples failed

This risk test sample was purchased from sampling points such as electric bicycle physical stores, after-sales maintenance points, and online e-commerce. 30 batches of products of different companies, brands, and models were randomly purchased in China, including 27 batches below 100 yuan and 3 batches above 100 yuan.

Results: Among the 30 batches of electric bicycle charger samples tested, 27 batches of samples were found to be non-compliant, with a total non-compliance rate of 90%.

Electric bicycle fires mainly occur during the charging stage

During the investigation, the reporter learned that 75% of electric bicycle fires occurred during the charging process: charger overload, electrical circuit short circuit and other faults were the main causes of fire. During the interview, the inspectors told reporters that there should be enough overload protection devices inside the electric bicycle charger. Once an abnormal fault such as short circuit, reverse connection or overheating occurs, the protection device can quickly fuse or block the current input, so as to effectively prevent the occurrence of fire and other dangers. In this risk monitoring, the inspectors first examined whether the overload protection device inside the charger of the sample was effective in the event of short circuit, reverse connection and other faults based on the "Special Requirements for Safety Battery Chargers for Household and Similar Electrical Appliances".

In the laboratory, the reporter saw that the tester first connected the positive and negative poles of a sample to the AC power supply in reverse, and then continued to power the sample. At 1 minute and 6 seconds into the test, the charger began to smoke; at this time, the charger still did not cut off the power supply, the wire temperature was still rising, and the smoke was increasing. After 2 minutes and 20 seconds, the charger circuit began to catch fire.

76% of the samples had circuit overheating, fire, explosion and other dangers.

After testing, 23 of the 30 batches of samples had circuit overheating, fire, explosion and other dangers in the abnormal working project test, and the non-compliance rate was 76%.

Cost-cutting on safety components is common

After technical analysis of the internal circuits of each sample, the testers found that most of the samples had the problem of cutting corners: 25 of the 30 batches of samples did not install any protection devices at the AC power supply end, and the non-compliance rate was 83.3%.

During the interview, the reporter learned that, in fact, for manufacturers, the cost of a fuse on the market is quite cheap, only about 2 to 3 cents, but some manufacturers just want to save these few cents of cost, but pass on the huge safety risks to consumers.

Housing flame retardant test: more than 60% of samples failed

In addition to the overload protection device, this risk test also tested the flame retardant performance of the electric bicycle charger housing. The results are not optimistic. More than 60% of the samples do not meet the flame retardant performance standards.

Since neither the national standard nor the industry standard for electric bicycle chargers has made requirements for the flame retardant performance of plastic housings, this risk monitoring was tested with reference to the national standard "Information Technology Equipment Safety Part 1: General Requirements". It was found that a considerable number of samples did not meet the flame retardant performance standards and immediately ignited after encountering open flames until they were completely burned out.

Outer shell flame retardant test: more than 60% of samples failed

After testing, 20 out of 30 batches of samples had their outer shells completely burned out during the plastic combustion test, with a non-compliance rate of 66.7%. The tester told reporters that the outer shells of electric bicycle chargers are mostly made of ABS engineering plastics. However, electric bicycle chargers have high power and high heat generation, and it is very easy for the outer shell to soften or even burn due to heat.

During the investigation, the reporter learned that it currently takes about 100g of plastic rice raw materials to produce an electric bicycle charger, and the cost of 100g of pure flame-retardant plastic rice is about 2.5 to 3 yuan; and the same 100g, the cost of plastic rice raw materials without adding flame retardants is only about 1.5 yuan, which is 30% to 50% cheaper than pure flame-retardant plastic rice raw materials. In order to save this cost of less than 2 yuan, some manufacturers choose to use plastic raw materials that are completely non-flame-retardant to produce electric bicycle chargers, leaving consumers with huge safety hazards.

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