I designed a system to power 20 odd catering vans, each with chest freezer, 2 tall larder fridges, lighting and payment system using solar power Mar-Oct - and on peak solar days in summer a 1kW hand hot water heater. Other times a Honda engined 3.4kVA LPG generator with automatic voltage regulator provides van power during opening hours and charges the batteries for overnight use.
This is the robust 3kW inverter which has a very high peak power capability (9kW), pure sinewave and 'sleep' mode when load drops below 75W and wake up when load rises above this figure which conserves battery power.
12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine - https://www.photonicuniverse.com/en/catalog/full/164-3000W-24V-low-frequency-pure-sine-wave-off-grid-inverter-peak-power-9000W.html
Batteries are Advanced Gel Matrix by Victron:
12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine - https://www.photonicuniverse.com/en/catalog/full/470-200Ah-12V-Gel-deep-cycle-battery-for-motorhomes-caravans-boats-and-off-grid-power-systems.html
Either 6 x 200Ah or 4 x 300Ah, wired in strings of 2 batteries in series to give 24V and these then connected in parallel. The theoretical power available from fully charged to batteries 'flat' is 12 x 1200 = 14.4kWh but this is not achieved nor relied upon. Instead the batteries are never discharged more than 50% to preserve their life; thus about 7kWh is the working amount of electrical energy available.
7kWh would run an 800W cooler
constantly for 7000/800 = about 9 hours.
This system is static apart from when the catering van is driven to and from site for its annual maintenance and refurbishment - the electrical wiring and electronics is only shaken about for a few hours each year. Of 20 vans we have only had one inverter failure which was on arrival not when in use and the supplier replaced it.
Don't operate at 12V. Use 24V and the cabling must be multi-stranded with properly crimped on ring terminals tightly bolted. One needs to buy a hydraulic crimper tool.
The amount of energy stored in each battery and then as a bank is
extraordinarily high and it is
highly dangerous if a battery or the bank is short circuited or if there is a fault current. Circuit breakers are essential and the battery must be located in an lockable enclosure. Special precautions, insulated tools and personal protective equipment are required when connecting up the batteries and high current 24 V cabling: this is a job for a skilled person. I wrote a procedure to do this which is followed to the letter.
The flat roof of the catering vans has a 1.5kW array of solar voltaic panels to charge the batteries.
On the mains voltage side everything has to be done to meet the IET electrical installation regulations and my client (brother in law) has to have annual certificates for inspection and testing including PAT of the electrical items for him to operate. We include the 24V dc and the solar photovoltaic wiring in the inspection and testing since it too can kill or harm just as much as the 240V.
I will not say more because I do not want to design your working safe system. There are safety features and programming of the inverter to do for the intended application. I suggest you contact Tom at Photonics Universe for further advice and an electrician familiar with off-grid battery to mains installations. I strongly advise against doing it yourself because you are not competent and do not know how to deal with all the risks.
PS: I am not saying this set up will satisfy your requirement. I have not done the analysis which should include whether you would be wiser to just use a generator to meet the business and operational requirement as distinct from the technical requirement.
