This article is intended as a reality check for safety with LiPo batteries as well as high speed moving parts. 

On Saturday the 25th we had a pretty good turn out for Heli Flyers at the field on the southeast heli area. Everything was going nicely for weather and the lack of crashes that day... That is until Rob began to spool up his Trex 600 electric heli. Rob went out to the flight line and started to spool up. He then went into Idle up mode which I assume is around a 2000 RPM head speed on a Trex 600. Approximately 2 seconds into idle up 1 the heli disintegrated.

The picture to the left is the mangled wreckage of Rob's Trex. It literally came apart like a bomb went off inside the canopy. After looking for 45 minutes or so we were able to identify that this was from a blade grip failure. The blade was found over 75 feet away in perfect tact with the bolt and nut still in the blade root. We made rough calculations that the blade was moving somewhere over 250mph and ejected with roughly 300lbs of force. Luckily it went away from Rob at the flight station and away from everyone sitting at the tables. We are thankful that Rob and everyone on site was OK.

I approached the battery long before we found the blade that had ejected. I picked it up and saw what appeared to be a pinhole in the battery. Upon closer inspection I noticed it had just started to smoke. I dropped the battery like a hot potato and yelled "We've got a smoker!". I was very aware that LiPo batteries can explode very violently. We all managed to back off. The smoke accelerated and the pack started to hiss, then spew fire like a torch. It burned for at least 15 minutes as it went from cell to cell igniting each individually. We found that the fire extinguishers were nearly empty so we waited for it to burn down a bit since the ground was wet from earlier rains in the week preceding. After it burned out I put dirt over it to suffocate the oxygen then eventually poured water over it. The water actually boiled and evaporated from the dirt after the pack was extinguished for about 15 minutes. 

This is What the pack looked like before I threw dirt on it. It was roughly 4 times its original size. The moral of this story is to beware of LiPos. Although our Helis and Planes look like toys, they can be quite dangerous and should not be treated as toys. Remember to store your batteries in a fire proof container as well as charging them in a fireproof container. Inspect your aircraft regularly for fatigued or worn parts and replace them.

I have embedded a video below showing several LiPo explosions as well as a fireproof charging bag with LiPos eploding in the bag. Watch it if you have never seen a LiPo explode. It will give you a new respect for the power a LiPo can unleash.

Be smart and be safe,

-Alex