mistakingly charged both at the same time. Charger was set for the 1500 Mah NiMh and the LiPo 150 MaH was still attached to the charger harness. Just didn't notice that the tiny 150 was sitll attached. Charger was seeing the 1500 not the 150 and therefore way over charged the 150 causing a global thermal nuclear meltdown of the 150.