How big a battery you need is important, but so is your charging system. And intended use.
Charge some batteries wrong and you will destroy them. A good example is an AGM battery, charge it fast with a high current you will boil the fluid and separate the jell from the fiberglass mat inside.
Use an auto starting battery in place of a deep cycle battery and it gets deep cycled a few times and you will destroy a battery.
There is a lot of things to take into account to get an off grid system to work right. It not as simple as just going to the store and buying a battery and then having a charger for it.
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You can run, but you'll only die tired.