“Other batteries don’t go this wrong when you treat them this badly,” said Jay Whitacre, an associate professor of materials science and engineering at Carnegie Mellon University. “The overall story here is these batteries are full of flammable electrolyte and they will burn if they are mistreated and something goes wrong.”
There was one lithium ion battery fire during testing of the batteries while Boeing was working with FAA on certification of the 787, said Marc Birtel, a spokesman for the aircraftmaker.
However, that fire was due to problems with the test rather than the batteries themselves, he said.
“There are multiple backups to ensure the system is safe,” Birtel said. “These include protections against over-charging and over-discharging.”
But John Goglia, an aviation safety expert and former National Transportation Safety board member, said, “It certainly sounds like based on what has been released so far that we have an issue of the battery charger or some other source providing too much energy to the battery.”
He said too-rapid charging might cause the electrolyte fluid in the batteries to overheat, leak and catch fire.
If the incidents are due to overcharging batteries, that might be good news for Boeing, Goglia said. A flaw in the aircraft’s electronics that permits overcharging would likely be much easier to fix than having to replace the aircraft’s lithium batteries with another kind of battery, he said.
Another possibility is a manufacturing defect in the batteries themselves, Whitacre said. More than other types of batteries, lithium ion batteries rely on very thin sheets of material internally to separate the negative and positive poles. The slightest flaw can cause a short circuit, overheating the flammable electrolytes.
“It’s a delicate ecosystem that you are creating inside it and you have to manufacture it with perfect integrity,” Whitacre said. “Then you have to keep it in the right voltage range and be very safe with its environmental conditions.”