and correct me if I'm wrong Prop but isn't that to do with VRB's...

and correct me if I'm wrong Prop but isn't that to do with VRB's only have one electro active ingredient so you don't get the cross contamination like other batteries which ultimately reduces other batteries capacity and life.
Plus lots of other plus's, from memory No fire risk. Work in wider range of temperatures. Can be charged and discharged at same time. Have the same strength ( my term, don't know the right one) when near zero charge as they do when fully charged. Can be left idle for long periods of time without any degradation.