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Lithium-ion batteries like the ones that overheated on two Boeing 787 Dreamliners can be made safe enough for even the most critical transportation uses, according to experts who spoke at a forum Thursday.

“Safety is improving year on year for this technology,” said Dan Doughty, of Battery Safety Consulting in Albuquerque, N.M.

The question is whether safeguards, such as extensive testing and building in protective circuitry, are too costly, Vince Visco, senior vice president of strategy and business development at Quallion, said in an interview. Los Angeles-based Quallion makes batteries for use in space and medical devices. He and Doughty spoke Thursday at a U.S. National Transportation Safety Board forum in Washington, D.C.

Boeing is proposing protections that include some of those Visco described in its redesigned battery, including titanium vents to draw smoke and fumes outside if a fire starts, as a way to get its grounded planes airborne. The U.S. Federal Aviation Administration hasn’t said when it will act on Boeing’s proposed fix.

The safety board, as part of an investigation into a 787 battery fire Jan. 7 in Boston, scheduled the forum Thursday and Friday to hear from academic, industry and government officials on how to make cells safer. It will hold a separate hearing April 23-24 to examine the Dreamliner’s battery design and how it was certified by the FAA.

Rechargeable lithium cells, which power devices ranging from Apple’s iPad to power tools, are increasingly being used in transportation equipment because they are lighter and hold more power than other battery technologies, NTSB Chairman Debbie Hersman said in her opening statement.

“Yet, lithium-ion batteries, like other power sources, such as the gasoline that powers so many personal vehicles, come with risks,” Hersman said. “These batteries are designed to produce energy — it is their very nature that poses the greatest risk.”

When they catch fire, lithium-based batteries may burn violently, spewing flammable gas and molten metal. However, batteries much larger than those on the 787 have proved themselves in recent years in uses that include hybrid buses and in power grids, said Yet-Ming Chiang, a Massachusetts Institute of Technology professor who also spoke at Thursday’s forum.

The industry increasingly understands the ways that batteries fail, which include internal short-circuits, overheating, manufacturing defects and damage during use, Chiang said.

“All of the major manufacturers try to test and plan for those failure modes,” he said in an interview.

NASA, which has used lithium-based batteries on manned space missions since 1999, performs extensive testing on each cell and takes steps to limit the chances of fire, said Judith Jeevarajan, the agency lead for battery safety.

Other steps, such as never fully charging a battery, limit the amount of heat discharged if a battery fails, she said.

“There is no reason to say that lithium-ion won’t have a place in high-consequence applications, such as passenger airplanes,” said Doughty, a former head of battery testing at Sandia National Laboratories.

The FAA has recorded 33 cases of batteries brought aboard commercial planes by passengers or as cargo catching fire since 2009. Of those cases, 26, or 79 percent, involved lithium-based batteries, according to the agency.

Since 2006, three cargo jets have been destroyed in fires where lithium batteries were present, according to the safety board. Those cells were being shipped and weren’t part of the aircraft. The United Nations’ International Civil Aviation Organization on Jan. 1 imposed new rules on air shipments of lithium batteries.

Manufacturers made 4.4 billion lithium-ion batteries in 2012, up from 800 million in 2002, George Kerchner, executive director of the D.C.-based Rechargeable Battery Association trade group, told the NTSB.

Airlines have told the FAA that on some cargo flights as much as 85 percent of shipments are hazardous because of lithium batteries, Janet McLaughlin, deputy director of the agency’s hazardous-materials program, said.

Boeing got U.S. regulators’ permission to install lithium-ion batteries on the Dreamliner in 2007, three years after passenger airlines were barred from carrying nonrechargeable types as cargo.