An inverter can draw from your battery bank and supply power directly from its outlets, or an
inverter that has a built in transfer switch can feed power to the main circuit breaker panel much as a home emergency generator can supply power to your panel during a power outage.
The transfer switch prevents a dangerous intermix of shore/generator power and inverter power blowing everything up.
If you are running 4 x 6-volt golf car batteries in series/parallel, you'll have enough battery to perform most 120 volt tasks while using the inverter, but some things, like a microwave or coffee maker can put a huge strain on the batteries.
Use this calculator to determine loads on your batteries. Remember that all 120 volt loads through an inverter are drawing from a 12 volt source, so voltage in this calculator, under these circumstances, is always 12 volts. In the case of the illustration inverter - 2500 watts at 120 volts - at full output it will draw 208 AMPS from the batteries to supply that power. The usable capacity of a 4 x 6-volt battery bank is about 250 AMP HOURS. At full load, you'd drain your batteries in about an hour and 15 minutes.
Of course, you won't apply those loads continuously, but a 1200 watt microwave and coffee maker running simultaneously will crush your batteries for at least the few minutes you run them.
If you suck power at anything like this rate, you need to replace it. That means a good generator, and better yet,
a sizable solar array for continuous charging during the day. (Illustration only. You may need more like 600 watts or more of solar.)
There's a LOT to this, but the calculator will help you analyze your needs and demands on your puny power source. Flooded cell batteries are VERY MEAGER power supplies. Compare to propane.
A 20 pound bottle of propane contains 412,200 BTU. 91,600 BTU/gallon x 4.5 gallons. That's 120 Kilowatt hours. That's 10,000 amp hours. (You need both calculators to get here.) Your battery bank may have about 250 usable amp hours. One tank of propane contains roughly 40 times the energy of your large battery bank.
For the record, I boondock exclusively. I have one 100 watt solar panel and one group 24 12 volt battery. I have 35 to 40 usable amp hours. Yet I'm able to run a 120 volt electric blanket (360 watts - 33 amps) for 20 minutes to take the chill off the bed and have enough for my furnace, pump, spark ignition for the fridge, hot water heater and furnace, and a rare light (we use lanterns to make this possible). No TV, stereo (we use a bluetooth speaker), and so on. All other 120 volt demands are served by the generator -- typically daily use about 30 minutes altogether.
Adjust your expectations according to your battery bank, your solar charging capacity, and your ability to tolerate the drone of a generator. And here's hoping you don't have a residential fridge.
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