The system is 24 Volts. Each battery is 6V so 4 are in series with 3 series in parallel. The small bundle of cord upper left in the box is extra length for the temperature compensation sensor. This is to optimize the charging profile depending on the ambient temperature. Though AGM batteries do not vent nearly as much as standard lead acid, the box still needs to be ventilated, with the fan turning on when the brains of the system detects charging.
If a person purchases quality batteries, and limits discharge depth, they will last longer than standard specifications advise. We run a 350+ feet deep water well, satellite internet and the basic stuff that modern life offers, but we do not waste, other than not really worrying about son leaving the bedroom and bathroom LED's light on. The aquarium heater is about 35 watts. It can add up but this system, and our mostly sunny climate (said to have more than 300 sunny days a year in nearby Albuquerque) usually gets less than 20% discharged a night. Really, when we get 3 days of clouds, using the old busted up generator is more for being gentle on the battery bank (more than 30% discharged) than any real need. We will also refrain from using the modest big screen TV during those cloudy times. We do have a 1500 watt electric heater in the bathroom, an induction cooktop, and a medium sized toaster oven but use an old school 2 slice toaster for bread.
WAY too much information but wanted to convey that many things about our family are normal. Local solar and electrical storage are not without environmental cost and expense. A backup generator can make a lot of sense for stopgap measures, but it is hoped that more people will adopt distributed energy production and reduce the significant line losses, as well as other factors related to the bureaucratic monopoly so many people are living under now.