The popularity of E-cigarettes, those battery operated inhalers that deliver nicotine without the smoke, is on the rise. But the $1.5 billion dollar business continues to battle a slew of health, safety and regulatory questions, including a new one related to battery safety.

A small number of consumer reports from across the country detail exploding e-cigs that launch out of their chargers, leading to fires and injury.

"I’m aware of 10 failures in the last year,” industry spokesman Thomas Kiklas, who represents the Tobacco Vapor Electronic Cigarette Association (TVECA), told NBC 5 Investigates. “When you charge them, they are 99.9 percent safe, but occasionally there will be failures.”

Kiklas said e-cigarette batteries can go through about 750,000,000 charge cycles in about a year. His estimate of fewer than a dozen incidents is only a guess.

Reported explosions remain miniscule compared to the number of battery-operated e-cigs in use in the U.S. But no central reporting agency exists to keep track of the data, so the total number of battery failures is unknown. Again the e-cig industry is confident the incidents are not common.

The jury is still very much out on other e-cigarettes questions, including their safety, health risks, and which, if any, federal agency should regulate them. Currently, e-cigarettes are only regulated by the Food and Drug Administration if they're marketed for therapeutic reasons. The FDA would like more regulation.

“Electronic cigarettes are battery-operated products that turn nicotine, which is highly addictive, and/or other chemicals into a vapor that is inhaled by the user," The FDA told NBC 5 in a statement.

"The FDA regulates electronic cigarettes that are marketed for therapeutic purposes as drugs or devices. The FDA intends to propose a regulation that would extend the agency’s 'tobacco product' authorities -- which currently only apply to cigarettes, cigarette tobacco, roll-your-own tobacco, and smokeless tobacco -- to other categories of tobacco products that meet the statutory definition of 'tobacco product.' Further research is needed to assess the potential public health benefits and risks of electronic cigarettes and other novel tobacco products.”

The FDA says it plans a proposal to adopt oversight of e-cigs, and to regulate them in the same manner as tobacco products, but did not say whether those changes included oversight of battery safety. They said their proposed changes could come as soon as this month.