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Creating the E-Bike Charging Rack That Earned an FDNY Exemption

CellBlock Safe Charge Rack

CellBlock's Safe Charge Rack system is recognized as a revolutionary breakthrough in micromobility battery charging. It's so innovative that it earned the very first exemption to an FNDY regulation governing how ebike batteries are charged. What follows is the story of how CellBlock created the first FDNY-allowed solution for charging ebike batteries.

The Seed Is Planted

When the FDNY released its fire code in April, 2023, CellBlock's CTO, Dylan Vandemark, pored over section 309.3. That's the section that governs the charging of “powered industrial trucks, powered industrial equipment and powered mobility devices“. He noticed in particular the requirement of two feet of separation between batteries as they charge. Vandemark immediately understood that it posed a serious challenge for scooter rental services, delivery services, and other operators that were responsible for charging up to thousands of batteries every day in a city where space is at a premium. Real world conversations with customers confirmed Vandemark's hunch.

Eric Frederickson, Managing Director of Operations for Call2Recycle, who partnered with CellBlock on the Safe Charge initiative, remembers how it started. “The Safe Charge Battery Rack grew out of an idea that was born after meeting with a customer on 35th street,” he said. “Their battery charging procedure was really a problem, and not only a code issue, but also a safety issue. As part of NYC’s fire code, e-bike or e-scooter batteries must be kept at least two feet apart in every direction while being charged. However, no one in New York has the space to do this. Also, even if you do have the space, you’re not protected if a battery fire occurs while charging.”

That planted the seed that ultimately bore fruit in our Safe Charge Battery Rack. Vandemark summed up the story at FDNY's recent “A Conversation with the Insurance Industry About Lithium-Ion Batteries” safety workshop. (Video at bottom.)

What is that story? Read on to discover how CellBlock created the very first FDNY-allowed solution for charging multiple micromobility devices in a limited space in New York City.

Designing the Safe Charge Battery Rack

Safe Charge Rack for storage charging and containment

Vandemark thought hard about how to engineer a solution.

He knew where not to start. Many CellBlock customers had been asking about an FM Approved solution. Those, however, exist to help mitigate the risk of external fires reaching ignitable liquids in an enclosure. A real solution would have to account for the possibility of thermal runaway inside the enclosure, from any one of multiple batteries. Furthermore, it would have to prevent that fire from propagating to other batteries.

The first and most crucial engineering choice was to create an open sided rack that allows easy access, but still provides sufficient protection for the batteries.

Each compartment was designed to include a top panel filled with CellBlockEX, our proprietary extinguishing agent. It would deploy automatically in the event of thermal runaway. It was important to have a passive deployment system, without the aid of electronics, because electronics might be destroyed in a fire. Vandemark arrived at a simple and elegant solution: contain the CellBlockEX  in a fabric that would quickly melt at elevated temperatures.

CellBlock Safe Charge Rack compartments showing deployment of CellBlockEX

As extra insurance, we created a FireShield cover made of proprietary textiles. This serves to further enhance the safety of the rack without allowing a dangerous buildup of gas and fumes.

Safe Charge Rack with FireShield cover

Testing the Safe Charge Rack

Since the field of battery safety is so new, there are no recognized standards. Because of this, CellBlock developed our own standards to test against. We decided to test our Safe Charge Rack both in-house and with a Nationally Recognized Testing Lab (NERTL) using a worst-case thermal runaway scenario.

Our initial tests were promising, but failures in the material separating the compartments pointed to where further modifications would be needed. Once we got that right, our subsequent tests revealed the danger of explosive gases. That's when we implemented the FireShield cover.


Ultimately we arrived at a design that satisfied even our own stringent requirements. This video illustrates exactly how the Safe Charge Rack contains and extinguishes a thermal runaway event and leaves other batteries in the enclosure unharmed.

Third Party Testing

The Safe Charge Rack successfully met our standards in our facility in Standish, Maine. However, we understood that third-party testing would be required before we could present our case to FDNY. That's why we brought it to CSA Group, a global leader in standards development and testing, and asked them to put the Safe Charge Rack through its paces. It passed with flying colors.

The Safe Charge Rack Becomes the First FDNY-Allowed Solution

After sharing the results with FDNY, CellBlock received a letter granting the Safe Charge Rack an exemption from the distance requirement in fire code 309.3. (Here's the pertinent excerpt: “Upon review of the application, the Fire Department has no objection to the use of CellBlock FCS's Charge Safe* Battery Rack”.)

Then, in July, we brought our Safe Charge Rack to FDNY's facility at Randall's Island. There we demonstrated its ability to completely contain and extinguish a thermal runaway event in a rack with multiple batteries. Watch:

Vandemark says, “Until now, even a fortified 10'×10′ battery fire area would be spatially inadequate for 50kWh of stored energy. Our Safe Charge Rack is not only the safest charging system available, but it also only requires 1/12th the space of other systems. Our team is excited to not just offer safety in storage, but also passive fire suppression. The space efficiencies and property protection with this system result in measurable cost savings. That may be the most impressive added benefit.”

And that's how CellBlock created the first FDNY-allowed solution for charging ebike batteries.

In addition to individual battery containment, the battery racks contain our proprietary battery fire suppressant CellBlockEX. CellBlockEX is deployed when fire is detected. (In a recent third-party test, CellBlockEX suppressed a thermal runaway in only three seconds.)

Design highlights:

  • Fire resistant barriers between each battery
  • Electrical outlet in each charging bay allows safe charging
  • CellBlockEX deployment system halts propagation
  • Equipped with heavy-duty locking wheels

Modular Convenience

The Safe Charge Rack is available in two footprints and may be ordered as 3-tier, 4-tier, or 5-tier.

  • Available in two footprints: 40.5″x32″ and 76.5″x32″
  • Available in three heights (depending on number of tiers): 49″, 63″, or 77″.
  • Heights are inclusive of locking wheels.
  • Each configuration includes the FireShield cover.
  • The 3 and 4 tier units may be upgraded to a higher tier.

FireShield: Extremely durable best-in-class textiles for extreme protection

The FireShield cover offers additional protection while providing easy access during business hours. Constructed from CellBlock’s proprietary textiles, these covers have been tested at over 1000ºC (1832°F) for 30 minutes. The back panel features a single zipper for access to power strips and charger cords, and the front panel zips on either side and rolls up when access is required. When fully zipped, the cover will contain flames and projectiles during a thermal runaway event. The FireShield cover has been engineered to mitigate explosion potential, and is included with every Safe Charge rack.

For more details, go to

*The product name was subsequently changed to Safe Charge Rack.

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