Lith ion batteries are completely DESTROYED by discharging them to full discharge depth. This is the best way to kill a lith-ion battery. See the chart. If you discharge Lith-ion to 50% DOD on a daily basis, this is a life of 15.89 years. Lith-ion batteries can also take and deliver huge charges. They can deliver more amps than than they can take in charging by about a 4 fold.