The new fire regulations prohibit electric bicycles from entering the house and charging, but charging in high and low temperature environments will seriously affect battery health and increase safety risks. This summer, the batteries that are "infected" in winter will enter the high-temperature charging environment in large numbers
Text | Yin Lu
Edit | mark
On February 8, Shanghai Putuo District, February 11 Beijing Changping District residential fires have occurred, Putuo District fire has been identified as the cause of electric bicycle charging, Changping District fire cause is still under investigation, but on the same day Changping District has carried out fire safety inspection work, focusing on electric bicycle illegal entry, into the building parking, charging problems. The two fires have once again pushed the safety of electric bicycle batteries to the forefront.
The safety of electric bicycles has been the focus of social concern in recent years, according to the data released by the Fire and Rescue Bureau of the Ministry of Emergency Management, a total of 18,000 fires caused by electric bicycles and battery failures were reported in 2021, resulting in 57 deaths. And because many electric bicycle fires have not ignited the surrounding items, most of the parties do not call the police, this data may be quite different from the actual data. In addition, some of the circuit overload fires caused by the charging of electric vehicles are counted as electrical fires, and electrical failures in 2021 are the first major cause of fire accidents, accounting for 28.4%.
On June 21, 2021, the Ministry of Emergency Management issued the Regulations on the Administration of Fire Safety in High-Rise Civil Buildings (hereinafter referred to as the Fire Regulations), which came into effect on August 1, 2021, article 37 of which clearly prohibits the parking or charging of electric bicycles in public foyers, evacuation walkways, stairwells and safety exits of high-rise civil buildings.
Banning electric bicycles into the house can indeed reduce the risk of inducing vicious fire accidents, but according to the investigation of the "Finance eleven" reporter, the current outdoor charging of electric bicycles generally lacks safety measures, especially in the first winter after the implementation of fire regulations, battery charging in a low temperature environment will have a serious impact on battery health, after the summer of this year, charging safety is not optimistic.
Outdoor public charging facilities have serious safety hazards
After the implementation of fire regulations in August 2021, the charging places of electric bicycles need to be all transferred to the outdoors, but before the outdoor completely did not have charging conditions, from the release of fire regulations to the beginning of the implementation, only 40 days, residential communities and other electric bicycles need to be intensively charged places, the charging facilities that can be set up are very limited, the public charging facilities that can be provided mainly include charging cabinets, adding power interfaces in the carport, and these two ways have more serious safety hazards.
Setting up a power interface in the carport is the simplest and most common, and the safety situation varies greatly according to different wiring methods. Qualified residential areas are equipped by the power department to install special meters, safety switches, power interfaces that meet the outdoor waterproof and dustproof level, and have basic safety guarantees, including fire fighting facilities such as fire extinguishers next to charging facilities in accordance with fire regulations. However, there are still some old residential areas that directly lead the power line from the property office or even the bottom commercial house to set up convenient charging facilities, which have almost no safety measures at all, and the hidden dangers are huge.
In addition, the charging methods of the three types of electric bicycle concentration places that are common in large-scale communities with dense personnel are mostly flying wire charging that leads to the plug board directly from the room, and the better conditions will be configured with shelf charging cabinets, that is, multiple power interfaces are installed on the shelves to directly charge the battery, but the power source is also mostly ordinary mains, and even the basic overload protection switch and other safety measures are not available.
Compared with the way to set up the power supply, choosing the charging cabinet as a public charging facility is the choice of more communities. Among them, several shared charging cabinets similar to the following figures have been rapidly popularized in many communities and have become the main way to solve the problem of charging electric bicycles for ordinary residents.
Charging cabinet in a residential area of Fengtai District, Beijing Image source: The official website of the little green man
A shared charging cabinet in a community in Futian District, Shenzhen Image source: Shenzhen release
Charging cabinets do play a positive role in solving the charging needs of ordinary people, but there are three main problems in such facilities: 1. Facilities can only be used for split batteries, which cannot solve the charging needs of all electric bicycles. 2. It is difficult to maintain the facilities, and there is a damage problem in the charging cabinet. 3, safety measures are limited, usually only the most basic overshoot, overload protection measures.
Charging cabinet in a residential area of Haidian District, Beijing, the cabinet door is damaged Photo: Yin Lu
Whether it is the installation of power interfaces or shared charging cabinets, the current public charging facilities have a common defect, the lack of temperature control means, and the biggest hidden danger of outdoor charging of electric bicycles is that charging under low temperature conditions will cause irreversible damage to the battery, and the risk of thermal runaway will increase significantly.
At present, most lithium batteries on the market are stated in the manual that the charging temperature should be between 0 ° C and 40 ° C, and it is not safe to charge the temperature outside this temperature range. By querying battery professional papers and consulting a number of battery experts, "Finance eleven people" have confirmed that charging batteries lacking temperature control devices below 0 °C will greatly increase the risk of lithium dendrites, and lithium dendrites puncturing the battery separator and causing short circuits are the main reasons for the thermal runaway of the battery.
Winter 2021 is the first winter after the fire regulations were implemented. According to experts from the Central Meteorological Observatory, the winter from the end of 2021 to the beginning of 2022, affected by the La Niña phenomenon, cold air activity is frequent, although the overall average temperature will not change much compared with previous years, but under the influence of cold air, there will be greater temperature fluctuations. The low temperature weather in the northern part of the mainland will increase compared with previous years.
Under such climatic conditions, the minimum temperature in most parts of the northern part of the continent is below 0 °C, especially public charging facilities are mostly set in backlit places to avoid direct sunlight, and the temperature is lower. Under such conditions, the battery that lacks temperature control means is charged, and the safety hazard caused by it is difficult to estimate.
Especially after charging at low temperatures in winter, batteries with impaired health will continue to charge in public charging facilities exposed to high temperatures after the summer of this year. For public charging facilities, it is not uncommon for the situation of less than 0 ° C in winter and above 40 ° C in summer, and it is not uncommon to charge outside the safe charging temperature range for a long time, and the battery safety hazards of electric bicycles cannot be ignored.
Most of the current public charging facility security measures are limited to passive defensive measures, such as requiring fire fighting facilities and setting them away from residential buildings, which are all efforts to control the spread of fires, and for battery safety itself, there are almost no effective measures at present.
Over-specification modifications are still widespread
According to the field survey of "Finance and Economic Eleven", in the four electric bicycle sales points in Haidian District and Chaoyang District of Beijing, the shopkeepers said that they can provide the service of brushing chips to lift the speed limit after the brand is listed, but the battery modification can only provide upgrade services that meet the new national standard 48V batteries, and there are not many over-specification batteries in the regular brand distribution stores of the bottom merchants in this residential area.
According to a number of riders, the electric bicycles they currently use can be divided into two categories, some riders have indeed begun to use vehicles that meet the new national standard, and some electric bicycle brands have also launched long-endurance models specifically adapted to the takeaway express delivery industry, with a mileage of more than 100 kilometers, while canceling various networking and other configurations, under the premise of achieving long endurance, try to reduce prices. Some battery companies have also launched large-capacity batteries that meet the new national standard, which can greatly improve the endurance without changing the original car circuit.
Most of the riders in the central urban area of the main activity area use models that meet the new national standard, and on November 1, 2021, after the official implementation of the new national standard for electric bicycles, the penalty for over-specification vehicles being confiscated is far higher for these riders than the cost of changing cars.
But outside the central city, there are still many riders who still use modified batteries. According to the rider, the manufacturer's declared 100 km endurance is only about 60 km left in the winter, and for the rider, the endurance of more than 150 km in the winter can ensure that their work will not be delayed by charging, so the over-specification modified battery is still very popular among riders.
The distance of single delivery in non-central urban areas is often more than 10 kilometers, and many riders also work part-time errands and other businesses, one-way may exceed 20 kilometers, the demand for long-lasting electric bicycles is more intense, so among these riders, through thickening pedals to expand the battery, install batteries in the space under the seat, remove the rear seat to install batteries and other means to achieve more than 200 kilometers in winter, non-winter more than 300 kilometers of endurance is not uncommon.
As for safety, the most representative view of these riders is, "We have more traffic accidents on the road than batteries, and if we catch fire, we will burn the car, and the accident will kill it", "Charging less twice and running more than a few orders is actually much more for us."
Through the survey, "Finance eleven" found that for industries such as takeaway and express delivery, the endurance of the new national standard electric bicycle is indeed difficult to meet their work needs. Under the size and weight restrictions of the new national standard, the maximum capacity of the battery used in the electric bicycle is about 48V26AH, which can achieve a theoretical endurance of about 120 kilometers. For riders with a single delivery of 3-5 kilometers in the central urban area, this endurance can barely meet the demand, but for non-central urban riders, the endurance is seriously insufficient.
Vehicle electricity separation, charging cabinet, and power cabinet replacement may be the best solution
How to solve the common safety hazards of electric bicycles, as the industry's head battery enterprises, Tianneng Battery, Chaowei Battery, Xingheng Battery and other enterprises, as well as the head of the electric bicycle brand, such as Maverick, Big Fish, Yadi, etc. will be car electricity separation and power exchange mode as an important solution.
The implementation of the new national standard for the separation of vehicle electricity is a good condition, in line with the new national standard specifications of the electric bicycle battery in terms of volume, voltage, current, power difference is very small, itself has a good standardization foundation, in the communication protocol, interface standards after the unification, you can achieve a more ideal power exchange foundation, even if it is still the use of similar to the current wired power exchange cabinet, in the unified communication protocol and interface standard conditions, to the power exchange cabinet new temperature control module is not difficult to achieve.
The more advanced power exchange cabinet is a in-line power exchange cabinet, that is, the battery is directly inserted into the power exchange compartment, the battery and the charging head are hard connected, rather than using wires for soft connection, the charging safety of this power exchange cabinet is better, and the space occupied is also smaller, and the temperature control performance of the power exchange cabinet is also better. However, the battery specifications are required to be highly uniform, and it is technically difficult to implement.
Compared with electric vehicles, the significance of power replacement for electric bicycles is more significant, because the outdoor charging conditions of electric bicycles are simple and there are many safety hazards, so for electric bicycles, it may be more practical to combine charging and replacing, and to change the main thing. Even if the power exchange scheme is not adopted, the vehicle electricity is separated, and the charging cabinet is used to charge it is more beneficial to battery safety. However, the premise is that the existing power exchange cabinet needs to be upgraded to make it have the ability to control the temperature and create a safe charging environment. At the same time, the power exchange scheme can also solve the problem of insufficient battery life in the takeaway and express delivery industries, and solve the practical needs of practitioners in these industries.
The safety hazards of electric bicycles require the joint efforts of the whole industry to promote improvement, and Li Wei, CEO of Big Fish Electric Vehicle, who previously focused on overseas markets, said at a forum that the safety impact of electric bicycles has been very serious. For example, when big fish is looking for top-notch live streaming KOLs such as Li Jiaqi and Wei Ya to talk about cooperation, electric bicycles are categories that are not considered at all, and even Luo Yonghao, who once brought goods for the calves in 2020, refused to stop for electric bicycles in 2021. The poor safety image of electric bicycles has seriously affected the further development of the industry. The introduction of the new national standard is the first step to solve the safety problem of electric bicycles, but it is far from enough.
The new national standard has made strict regulations on physical specifications, electrical standards, and safety protection, but these regulations alone are not enough to change the current situation of electric bicycle battery safety hazards, and the whole industry should also make further efforts in communication protocols, interface standards, overcharge overload protection, and temperature control systems. Achieve a comprehensive improvement of the battery safety level of electric bicycles.
The author is a reporter for Caijing
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