As my 1 year old battery supply started to die I bought 4 LG HG2s for replacement. I thought I had a dud when one of them ran out of gas 2/3 of the way through a 5.5ml tank twice. Then it would not charge completely. I was about ready to pitch it but gave it one last try after it finally took a complete charge. To my surprise it lasted the whole tank with about 1/8 of a bar left. Is this common or a fluke?