Within reason, there is never too much battery available. More batteries cost more, take up more room and weigh more. But the more battery power, the longer the UPS can operate without an external source of power. One solution is to have two to four hours of backup battery available and have a generator that can be used to recharge the batteries and run your systems after the batteries have been depleted. For larger installations, it is sometimes more economical to use automatic-starting generators rather than using more batteries.