LiPo fire
Carlos Reyes
It was not a new battery pack. I had just made the first flight of the day using it. The landing was hard, but not excessive. Before the fire started, the airplane had not sustained any damage.
The cells hissed and emitted clouds of thick white smoke. It's a large battery pack, and the cells took turns burning one after the other. We used an ABC fire extinguisher on the airplane, but I'm not sure it made any difference. Other than some scorching, there was no other damage. The battery pack pretty much was gone.
The battery pack remains were placed in salt water for a week before their final disposal. A good ratio is one cup of salt per gallon of water.
After the incident, I researched LiPo safety. Something I did not know is that it can take a few minutes for a fire to start after a crash. That was not our case - the fire started right away. But a fire could start ten minutes after a crash. Besides the fire extinguisher, we now also have a fire proof container where a suspicious battery pack can be placed for a few minutes after a crash.
Carlos Reyes, AMA Scientific Leader member #4601
Author of RCadvisor's Model Airplane Design Made Easy and other books.
www.RCadvisor.com founder - Brainy calculator, so you don't have to be.
Dan Tandberg
fireproof ammo box? Or did you leave it in. Was this at the field on
grass or asphalt? What was the brand, number of cells, and capacity.
Was it protected or was it one your of you "battery hanging out" type
foamies. What was in front of the pack that it could have hit into
during the landing. How was it mounted? could it have moved foreward
during the landing and hit something hard?
Carlos Reyes
The battery was in the model. The first white cloud went up a second or two after the model hit the ground. The landing was on a field with short grass and soft ground (it had rained). The part of the fuselage where the battery was located was made out of aircraft plywood. This model has no landing gear. We have flown it many times before and since without any other fires.
The fuselage does not contain any sharp protrusions that could have punctured the battery. In fact, that landing was pretty much a flat plop onto the ground. The airplane was right side up and the flat bottom of the fuselage touched down first.
To prevent damage to the battery in a nose-in landing, we normally put a large foam block in front of the battery. Again, this was the first flight of the day with that particular battery pack. To keep the batteries from moving, we put foam pieces on their sides. The space where they are located already provides a tight fit up and down and back towards the tail.
It had not been a very long flight. In fact, as I recall, I had aborted the flight about 30 seconds after takeoff for unrelated reasons.
They were Thunder Power ProLite cells. This particular pack consisted of 6x 2000 mAh cells.
We cannot see any obvious reasons for why the pack failed. The only obvious guess that we can make is that the pack was already compromised in an earlier flight.
As a side note, I have been doing battery capacity testing. I have a battery cycler and all of the battery packs have been tested for proper capacity. This particular pack had checked out okay when I tested it a week or two before the incident.
Battery packs that have been deformed ("dented") from crash damage usually show reduced capacity and are safely disposed of.
Carlos Reyes, AMA Scientific Leader member #4601
Author of RCadvisor's Model Airplane Design Made Easy and other books.
www.RCadvisor.com founder - Brainy calculator, so you don't have to be.
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