The invention provides for an energy storage system that has a first plurality of battery cells that each are capable of a first C-rate. The plurality of battery cells can be charged at an equivalent rate on a kWh/minute basis as a second plurality of battery cells that each are capable of second C-rate, with the second C-rate being higher than the first C-rate. The first plurality of battery cells may have an energy storage capacity which is approximately twice the energy storage capacity for the second plurality of cells.