Recently updated for more efficient and stronger battery life.  These are the standard AGM 48V (Combined) battery pack that is installed with all ECS Motor Kits.  Sold as a complete set, as it is not reccomended to replace single batteries intermitantly.  These can be used to replace your original motor Batteries as they get ran down over time.  Remember, Batteries are a fuel source just like gasoline in your car.  But you get to re-use that gas over and over until it isn't powerfull enough anymore.  Even normal use will eventually wear these down and require replacement after a certain # of charging and use cycles.  The care and charging of these batteries strongly determine the life cycle of the batteries.  Lower depletion between charges, temperature, and consistant proper charging/maintaing are all important to extend the life and power of your fuel source.  For a diagram of charge rate vs depletion please contact us.  Additional cables may be needed to instal if existing cables are corroded or different length.  Any questions and we would be happy to help and get you everything you need for the job.