Forget RCM...high amp draws usually occur on boats ONLY with windlasses and
starters and for brief times. You get MUCH less total power out of a deep cycle battery when you put a heavy load on one so the 20 hours rate is what we use in sailing applications as Bill clearly illustrates. I concur with the rest of his post but would also offer some other thoughts.
225 AH's effectively requires you to recharge daily based on your use estimate. 500 amphours would string that out over more than a weekend...so think about how LONG you wish to be self sustaining without a re-charge.
The Golf cart batteries in series may be suitable solution bt te space available in your boat may suggest a different approach.
Group 31 batteries (12V) generally deliver around 100AH's each
Group 4D batteries ...about 155Ah's
Group 8d batteries...about 250
Here are 31/4D and 8D approximate dimensions for reference:
.................................................. ..........31.........4D............8D............. ..........
| Length |
|
|
|
| 13.0...
| 20.75... | 20.62 |
|
|
| inches |
| Width |
|
|
|
| 6.72... | 8.75.... | 10.95 |
|
|
| inches |
| Height |
|
|
|
| 9.44... | 9.88... | 10.17 |
|
|
| inches |
|---|