A woman was injured Saturday in a fire apparently caused by the failure of her home’s battery backup system after the power went out in Sanbornton, an example of a new concern for fire departments and building inspectors.

“We’re going to have growing pains with these new types of systems being installed,” said Sanbornton Fire Chief Paul Dexter Jr. “I’m envisioning some changes to our code enforcement with regard to those types of systems.”

The system had been installed about three years ago by a licensed electrician in the mechanical room in the house at 9-a Knox Mountain Road. It consisted of three used lithium-ion battery packs taken from Chevy Volt cars that powered certain systems, including the well pump and the heating system when electricity from the main grid was out.

“She had been running the batteries due to a power outage,” Dexter said.

Power had returned and the homeowner had shut the batteries off transferring everything back to the grid when she heard a “popping” sound coming from the mechanical room, which was adjacent to the one-bay attached garage.

“When she investigated and opened the cabinet where the batteries were stored, the bottom battery was ‘bubbling over’ ” Dexter wrote in a press release. “The owner went to get a fan in an attempt to cool the batteries but when she returned the battery was on fire and extending to the ceiling, she immediately went and called 911. In an attempt to remove a vehicle and tractor from the garage, she sustained minor burns and smoke inhalation and was transported to Concord Hospital – Laconia and later released.”

The resulting fire collapsed the garage roof and destroyed the batteries.

It appears the battery entered “thermal runaway,” in which the heat produced by electricity production is not released as normal but builds up until the system causes the lithium, which is very flammable, to ignite.

It’s not clear why thermal runaway occurred in a system that had operated without issue for three years. Dexter noted that because the batteries were bought used, “we don’t have any idea how old they were.” The contractor who installed the system is no longer available, Dexter said

Car batteries contain a large amount of usable energy even after they can no longer produce enough electricity to move the vehicle. It is becoming common to transfer them from vehicles to what is known as stationary energy storage, where they can provide electricity backup or grid stabilization. This process forms the business model for at least one startup company.

Dexter is also the code enforcement officer in town and says battery backup systems are still rare. “We’re doing a ton of generators in town, but we get very few calls to inspect battery systems,” he said.

Sanbornton, which has about 3,000 residents, has no building inspector, which is the case for many small towns in New Hampshire.

Dexter noted that in New Hampshire, code inspectors don’t do electrical inspections. They come under the purview of the state licensing board, which licenses electricians. The only systems that Dexter has to inspect use liquid fuel.

“We do permitting and inspections on gas installation, oil installations, propane tanks. We do generators but only do the gas side of the generator … we don’t inspect the electrical connection,” he said.

This practice developed because of the dangers of explosion and carbon monoxide poisoning involved when oil- or gas-fired systems are improperly installed. The growth of battery systems, which involved different sorts of dangers, may require the old inspection regulations to be changed.

This is similar to changes necessary as electric cars become more common. Although electric car fires are much less common than fires involving internal-combustion engines and do not carry related dangers such as the spread of flammable gasoline after crashes, they may not respond to established firefighting techniques.

“It normally used to take 1,000 gallons of water” to control a car fire Dexter said. “I’m hearing anecdotally other fires taking 18,000 to 20,000 gallons to put out car battery fires.”

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