A battery bank is the number of batteries required by the inverter in the long run to serve efficiently. The number of batteries used depends on the inverter quality and capacity. A good inverter can use anywhere between one to 30 batteries in its lifetime. The company generally specifies its bank capacity. The backup time can also be increased by adding more batteries. In other words, an increase in the battery bank size may increase the backup power. However, it should be noted that the batteries with 12V should be used.