I connect a UPS to a generator allowing me to safely power my sensitive electronic equipment (laptops) when in remote locations, generators are not perfect and occasionally the power fluxuates causing spikes, over and under voltage issues. To resolve these issues and make it safer for my sensitive devices I use a UPS which provides a cleaner and more reliable energy supply. When a under voltage occurs the UPS boosts the power using the battery, when this happens (which is often) the UPS beeps for an extended period (indicating it is using the battery, which I don’t really need to know as it’s only for a couple of seconds normally).