I've got 4x deep cycle batteries with over 300 amp hour storage and I think it is a bit of an overkill. In theory I could draw 10 amps continuously for 30 hours. In a week's use being on the boat, without charge the batteries drop down to 80% from a full charge.

I recon, I could do with only 2x. And they are old fashioned led batteries needing maintenance at least once a month and are not sealed to my liking. But they work and are relatively new. I would think sealed or AGM batteries would have been a better choice.

How much amperage is enough?