NEW YORK (CBSNewYork) — Keeping phones and tablets charged is a challenge of modern life, and portable battery packs are a common solution.

But as CBS2’s Ilana Gold reported Friday, they can possess a hidden danger.

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“Once, I felt my knee actually burning,” said Michelle Grace. “It sort of had a little flash back on my jeans, and that’s when I knew, wait, something’s happening.”

The aftermath told Grace’s story. A rug was left scorched by fire, and charred pieces of the batter pack were strewn all over her apartment.

There were also burns on her clothing and skin.

“Very scary,” she said. “Very scary.”

Grace had been using a rechargeable device to keep her smartphone powered. She said when she went to plug in the USB cord, the battery blew up.

“It all happened so fast. I turned around and my couch was on fire — full on flames,” she said.

Grace had bought a $30 lithium battery pack from a popular retailer.

The Consumer Product Safety Commission has more than 540 recalls or complaints involving all types of charging devices. A CPSC report said one charger exploded and caught fire, burning two significant holes in the bedroom carpet.

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“If the battery is fully charged, the fire is more intense,” said engineering professor Yan Wang.

Wang has conducted experiments on lithium battery fires.

“They can hurt people,” he said.

Although such fires are not common, Wang said problems can occur in older devices with battery management systems that no longer work. They keep taking a charge even when they are 100 percent full.

“You have overheating, and fire, and explosion eventually,” he said.

In another concern, many products sold today are cheap imports or hard-to-detect counterfeits.

“Some of the products are not of the high standard, and potentially can be dangerous,” Wang said.

As for Grace, she is just thankful her explosion was not worse.

“Had I been on an airplane, or if had small kids that were around, that would have been extremely frightening,” she said.

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The Federal Aviation Administration is now telling travelers to keep the devices out of their checked package. The agency is also looking into banning the battery packs as cargo on passenger planes.