Cycle life refers to the number of cycles of charge and discharge that the battery can withstand before it dies. Cycle life is referred to as ‘No. of cycles’ at a certain ‘DOD or Depth of discharge’ It can vary from as low as 300 cycles at 80% DOD for an SMF to as high as 5000 cycles for some specialised batteries like submarine batteries. Most good manufacturers will provide details of float life as well as cycle life at different DOD’s by means of a graph.