The cycle life and cycle duration are important factors in determining how long a 5 kWh battery will survive. Before their performance starts to decline noticeably, most kWh batteries can cycle about 5,000 times. A 5 kWh battery can, however, last for 10 to 15 years. How long does it take for solar batteries to charge? A panel can normally charge a completely discharged battery in five to eight hours. The overall charging time will change based on the battery's condition. A solar panel may re-energize the cells of a battery within five to eight hours if the battery is completely discharged.