Thanks guys,sorry for leaving out it's for a quadcopter. I'm looking to buy new but, a good used would be ok too. Richard that batt looks good, I don't know what brands are better than others. Let's say Duracell to eveready. My machine is running with 3cell. Can I use four cell or do I need to change things. I'll order that batt tonight Richard, just have to change to bullet connectors, xt60. Thanks