The best part about them is that you can hook them up in series when you charge them so you can still charge that 6.6 volt 6900 mah pack up in 15 minutes. Think about running for 20-30 minutes & charging in 15 minutes. Oh yeah, my 6.6volt 6900 pack set me back about 1/3rd of what a max amps 8kmah lipo would.