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?

Hi All,
As part of redesigning my battery and charging system, I have built a spreadsheet (Windows 7) to explore the status of a battery bank under different scenarios such as nighttime motoring, day sailing, anchoring,etc.

Please see the attached screen shot.
The spreadsheet allows you to set up a scenario and enter variables such as the current drain of various pieces of equipment you will use , what percentage of time it is used, the current from charging sources, your battery size, its initial state of charge, etc, etc.
The spreadsheet calculates the status of the battery at the end of the scenario

I have color coded the cells containing formulas Red, and cells which are not colored are for user input. All other colors are for titles.
I have included comments in some cells, but hopefully the spreadsheet is self explanatory.

The values in the spreadsheet as shown are for my boat and yours will probably be quite different - you can change them to suit your requirements.

At present, I can't see how to upload the file to the forum - if anyone knows how, please enlighten me.

Meantime, anyone who would like a copy need only pm me & I will email it as an attachment.

regards,
Allan