A simple steel bucket isn't enough, lipo burns pretty darn hot, place it in a ceramic pot or a charging bag made for lipo's, and when they do explode, stand way back. One guy at the field was charging his 2500 MAH 3s lipo and it was sitting on the top of the crossmember for the radiator( engine off for hours) and it went off. One cell of the 3 shot off like a roman candle, the other 2 went between the radiator and the engine and burned most of the wiring down there. That was a crappy day scrambling for water and a fire extinguisher.