A Rad Power Bikes rider, alarmed by reports of e-bike lithium-ion battery fires, shared a homemade storage solution on Reddit this week, sparking a broader discussion about how to safely store the devices.

The post, shared in a Rad Power Bikes forum, shows a battery placed inside stacked and capped cinder blocks — a low-cost, do-it-yourself attempt to contain a potential fire. The idea resonated with riders who said they were uneasy about storing high-powered batteries inside homes, even as others questioned whether the setup would actually work.

Eric Stahl of San Francisco has owned his Rad Runner Plus e-bike since 2021. For the past couple of days he’s been engaged in a back-and-forth debate with “armchair engineers” about his solution.

“What I put on Reddit is a cheap, DIY, common sense solution,” he told GeekWire. “It’s not tested. It’s not proven. I’m not an engineer or an expert. So everyone needs to proceed at their own risk.”

The fire concerns come amid heightened scrutiny of e-bike battery safety. Last November, the U.S. Consumer Product Safety Commission issued a warning urging consumers to immediately stop using specific lithium-ion batteries for several Rad Power Bikes models, saying the batteries could “unexpectedly ignite and explode” and pose a fire hazard. The warning followed dozens of reports of battery-related incidents and property damage.

Seattle-based Rad Power Bikes disputed the agency’s characterization and declined to agree to a recall. Since then, the once high-flying startup has entered into bankruptcy protection and is in danger of an imminent shutdown following surprising news in November that it was fighting for survival amid “significant financial challenges.”

Seattle Fire Department officials say the anxiety among riders is understandable as lithium-ion batteries used in e-bikes and other micromobility devices have become a growing fire-safety concern.

“Lithium-ion batteries store a lot of energy in a compact device,” SFD Public Information Officer David Cuerpo told GeekWire. He said they can burn extremely hot and very fast when failures occur.

Seattle firefighters began formally tracking lithium-ion battery fires in 2022. Last year, the department responded to 43 fires involving batteries, according to Cuerpo. Those incidents involved a range of devices, from phones and laptops to e-bikes and scooters.

Fires can be triggered by physical damage to batteries, corrosion, electrical failure, or exposure to extreme temperatures. When a battery fails, heat can spread rapidly from one cell to another, potentially creating a cascading fire.

Depending on where bikes and batteries are stored in the home, Cuerpo cautioned that improvised solutions can introduce new hazards.

Without full details on the cinder block setup shown on Reddit, Cuerpo said it did not appear to be a foolproof solution he would recommend.

“When a lithium battery catches fire, it can burn in excess of 1,800 degrees Fahrenheit. That’s really, really hot, and that burns very, very quickly,” he said.

Another major concern is the release of toxic, flammable gases during a battery fire. A homemade solution that’s not airtight could increase the risk that dangerous fumes escape into an enclosed space.

Stahl said his main goal was to prevent a fire from spreading to his house.

“I have it in my garage with a smoke detector above it, so if I’m home, I’ll hear the detector, see/smell the smoke and open the garage door if needed. If I’m not home I’m less worried about the fumes,” he said.

Even when flames appear to be out, the danger may not be over, Cuerpo cautioned. Seattle firefighters have encountered batteries that reignited hours or days after an initial fire, as undamaged cells continued to heat up.

Cuerpo recommends storing lithium-ion batteries in a cool, dry location out of direct sunlight, ideally in a garage and away from combustible materials. Commercial storage containers designed specifically for lithium-ion batteries are the safest option, though he acknowledged they can be expensive. A number of fire-retardant battery bags and certified fire-resistant storage boxes — some tested to independent safety standards — are sold online and through specialty retailers.

Cuerpo also urged riders to use manufacturer-approved chargers or equipment tested by independent certification agencies.

Batteries should be checked at least once a month for warning signs such as swelling, cracks, unusual heat, residue, or odors. Damaged batteries should never be thrown in the trash, where they can ignite fires when crushed in compactors or garbage trucks. In Seattle, residents can dispose of lithium-ion batteries at hazardous waste facilities operated by Seattle Public Utilities.

Rad provides battery safety guidance on its website, advising riders how to store batteries, to follow recommended charging practices, and to consult its battery guide and owner’s manuals for proper handling.

Stahl, who said his Rad battery model number showed up on the Consumer Product Safety Commission’s warning list, is careful about how he handles his device.

“It’s not good to drop them or get them soaking wet, but mine has been on my bike the whole time I’ve had it,” he said. “If it was cracked or bulging I would definitely get rid of it.”

He’s eager for someone to actually test his cinderblock solution with a real (safely monitored) battery fire, and maybe post their findings in a video on YouTube.

“There is so much bad information on the internet about this stuff. I just want truth-seeking,” Stahl said. “It would be a huge public service for someone to test it — and if it works, get the word out.”