In New York City, USA, you can almost encounter an electric bicycle every few blocks, whizzing by you.

In recent years, electric bicycles have become increasingly popular, especially among couriers. Thousands of couriers ride them through the streets of New York every day.

However, the surge in the number of electric bicycles has led to many fires caused by batteries, some of which have even resulted in deaths.

Now, the New York City government hopes to avoid more fires by replacing batteries. A pilot project will provide a few couriers with an alternative that does not require charging, including the deployment of exchange stations that provide fully charged batteries.

Supporters say that the plan can lay the foundation for a new model of power supply for small electric vehicles in the city, which is both convenient and can reduce the risk of fire.However, considering the vast number of batteries we use in our daily lives and in areas such as electric bicycles, the path to fire safety may be long and winding.

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According to statistics from New York City, the number of fires caused by batteries in the city increased nearly ninefold between 2019 and 2023.

People are becoming increasingly concerned about battery fires. In March 2023, New York City Mayor Eric Adams announced a plan to address the issue, which includes regulatory measures for electric bicycles and their batteries, cracking down on unsafe charging practices, and providing assistance to delivery personnel.Although there are various reasons for battery fires, many incidents seem to be caused by the charging of electric bicycles in apartment buildings, including a major fire in February 2024 that resulted in one death and 22 injuries.

To address the charging issue, New York City has launched a new pilot project, with participants being couriers who use electric bicycles.

Over a period of six months, 100 delivery drivers will be matched with one of three startups, which will provide a solution that does not require charging within apartment buildings.

One of the startups, Swiftmile, is building rapid charging stations similar to bicycle racks, which can fully charge an electric bicycle in two hours.

The other two companies, Popwheels and Swobee, are proposing a different, potentially faster solution: battery swapping. Riders can swap a depleted battery for a fully charged one instead of waiting for it to charge.The solution of battery swapping has been applied to electric vehicles, but it is mainly concentrated in Asia. Chinese car manufacturer NIO operates a network of battery swap stations that can replace the car's battery in less than three minutes.

Gogoro, one of the climate technology companies selected by MIT Technology Review for 2023, has a network of electric scooter battery swap stations that can support more than 400,000 battery swaps per day.

Popwheels co-founder and CEO Baruch Herzfeld said that this concept needs to be adjusted according to the actual situation in New York and for delivery personnel.

"But if we achieve it," he said, "we believe that everyone in New York will be able to use small electric vehicles."

Battery swap networks like NIO mostly only include a company's equipment, allowing the manufacturer to fully control the vehicle, battery, and swapping equipment. This is because the key to achieving battery swapping is the universality of the fleet, with many vehicles being able to use the same system.Popwheels co-founder and president David Hammer stated that fortunately, delivery drivers in New York City have already formed a fleet.

It is estimated that about half of the more than 60,000 couriers in New York City rely on electric bicycles. Many of them use Arrow-brand bicycles equipped with detachable batteries.

For couriers with tight working hours, convenience is of utmost importance. Irene Figueroa Ortiz, a policy advisor at the New York Department of Transportation, said: "For many people, battery charging and battery replacement are just technical differences. But for couriers, it is about their livelihood."

To complete the pilot project in New York, Popwheels is building battery cabinets at multiple locations throughout the city, including 16 electric bicycle battery charging slots.

Passengers will use a smartphone app to open the cabinet door, insert the used battery, and then take out a fully charged battery from another slot.Hammer said that, according to the company's estimates, each cabinet should be able to support 40 to 50 riders.

Hammer said: "Perhaps this will bring a larger vision, integrating battery swapping as part of the city's future.

But for now, it is addressing a very real and pressing issue faced by couriers, that is, how can they work a full day, earn a reasonable salary, and not risk their lives to the danger of battery fires."

An increasingly serious problem.Lithium-ion batteries power products such as laptops, mobile phones, and electric vehicles (including cars, trucks, and electric bicycles). A major advantage of their battery chemistry is energy density, which is the ability to pack a large amount of energy into a small container. However, all methods of energy storage can be dangerous.

Batteries can catch fire during charging, use, or even storage. Generally speaking, fires occur when the temperature around the battery rises to unsafe levels, or when the battery has a physical problem that causes a short circuit, preventing the normal flow of electricity. These factors can trigger a dangerous process known as thermal runaway.

Most batteries are equipped with a battery management system to control charging and prevent temperature spikes and fires. Ben Hoff, the head of fire safety engineering and hardware design at Popwheels, said that if this system fails, or if the battery does not have this system installed, charging can lead to a fire.

At the end of February 2024, some couriers who participated in the New York charging pilot program registration event said that one of the reasons they were looking for battery alternative solutions was safety.

"I'm really worried about this," Jose Sarmiento, a long-time courier, said at the event. "Even when I'm sleeping, I'm thinking about the batteries."Hammer of Popwheels said that replacing the battery could also make electric transportation safer. The company strictly monitors the batteries they provide to riders, and their monitoring system includes temperature sensors installed in charging cabinets.

If the battery overheats, charging can be stopped immediately. If a fire happens to occur inside the charging cabinet, an aerosol fire suppression system can slow down the fire.

The batteries provided by Popwheels are also UL certified (translator's note: UL is the abbreviation for Underwriter Laboratories in English), which means they must pass third-party safety tests.

Hammer said that New York City banned the sale of uncertified batteries and electric bicycles last year, but many riders are still using them.

Michael Pecht, a professor at the University of Maryland who studies the reliability and safety of electronic equipment, said that low-quality batteries are more likely to cause fires, and this issue can usually be traced back to the manufacturing process.Pei Qiet explained that battery manufacturing facilities should be as clean as medical operating rooms or semiconductor manufacturing facilities. Over time, dust and dirt in the batteries can cause big problems, because the charging and discharging of the batteries can lead to subtle physical changes.

After enough charge cycles, even tiny dust particles can cause a short circuit and trigger a fire.

Poor manufacturing processes make batteries more prone to catching fire, but it is a daunting task to strictly control the large number of batteries produced each year.

Large manufacturers can produce billions of batteries each year, which makes the solution to battery fires complex, Pei Qiet said: "I think some people just want a simple answer. For me, there is no simple answer."

New projects that provide well-manufactured batteries and strictly control the charging process may reduce safety issues. But to make real progress, it is necessary to rapidly and significantly scale up, while formulating regulations and constantly engaging with the community.Popwheels needs to install hundreds of battery swap cabinets in New York City to support a sufficient number of couriers. The pilot program will help determine whether riders are willing to use this new charging method, as it concerns their livelihood.

As Hammer said, "If they are not willing to use it, then this technology is meaningless."