CHARLESTON AIR FORCE BASE, S.C. –
The Block 15 aircraft battery began to deteriorate during routine maintenance into a condition known as thermal runaway. The battery became dangerously hot, emitted an excessive amount of hydrogen gas and began spewing electrolytes everywhere. At this point, the battery was self-destructing and if something was not done shortly, the hydrogen-rich atmosphere could have become explosive.
It was an event like this that Master Sgt. Michael Bunting, 315th Maintenance Squadron electrical and environmental systems craftsman, and Senior Airman David Stricker, 437th Maintenance Squadron electrical and environmental systems journeyman had to overcome before a major disaster happened within the electrical and environmental battery shop.
"It was mentioned in our career development course that a thermal runaway could occur," said Airman Stricker. "I didn't have much experience with this type of situation. I had to make decisions based on theory, so I did what I thought was right."
Airman Stricker was preparing the aircraft battery for a capacitance check, which checks the ability of a battery to hold a charge. While the battery was recharging, Airman Stricker smelled a bitter aroma.
"The battery started to give off a distinct acrid smell, which told me something was wrong," said Airman Stricker. "I knew I had to stop the charge or risk possible damage to the battery or worse."
Immediately after shutting down the charger, Airman Stricker exited the room to inform Sergeant Bunting about what was happening with the battery.
"I have been doing this for 25 years and I have never seen this type of situation occur," said Sergeant Bunting. "It is rare that this situation could actually happen and something you typically only see the after effect of. Initially, I was scared of what I saw because the room was filled with smoke. My first thought was to open the door so hydrogen could escape. Then I wanted to keep the electrolytes from spewing out of the battery so it could not set off the remaining cells and, finally, I wanted to try to remove the [bad] cell so it could not ignite the other cells. I would rather lose one cell versus 20."
Sergeant Bunting immediately recognized this was the beginning stages of thermal runaway. He immediately grabbed a syringe and extracted the overflowing fluids from the battery. Sergeant Bunting determined he must immediately disconnect the bad cell from the remaining good cells and quickly instructed Airman Stricker to move outside the charging room, who insisted that he remain and assist in disarming of the cell.
"I asked Airman Stricker to leave, but he refused and I did not have time to argue with him," said Sergeant Bunting. "When working at Trident Technical College I had a hypothesis that if you were to remove the melting cell you could save the rest of the battery."
Sergeant Bunting and Airman Stricker immediately began removing the connector links from the cell. These connector links are used for shorting cells together - similar to how flashlight batteries are stacked on top of one another. They were careful due to the shock and spark hazard of the fully charged surrounding cells and carefully extracted the link.
"The fixtures are metal and the components are metal, so we have to be careful not to create a spark while removing the cell," said Sergeant Bunting. "It turned out that I actually needed his help. Think of the operation game ... instead of the red nose, it would have been a big fireball."
The cell removal now prevented any possibility of thermal runaway on the remaining cells in the aircraft battery.
"If all 20 cells of the battery would have went into thermal runaway, it would have released a lot of hydrogen, which could have gone off at any moment and ruined a $10,000 battery," said Sergeant Bunting. "If there would have been a source of ignition it would have blown the roof off the building."
Sergeant Bunting's and Airman Stricker's jobs are not always this dangerous at the 437 MXS electrical and environmental battery shop. At the shop they typically repair aircraft electrical and environmental systems. This usually consists of air conditioning, generating systems and anything else electrical.
"These amazing Airmen had to put themselves in danger disassembling a fully charged battery, using a make-shift insulator," said Maj. Sara Huiss, 437 MXS commander. "Sparks were flying everywhere and without their heroic efforts there would have been a big explosion and fire. If there would have been a fire, all the batteries would have been destroyed. Their calm demeanor and quick thinking saved the mission, the building and themselves from disaster ... they are truly heroes."