the size of the battery bank is much more to do with what you need to take out of the system, rather than what you use to put it in!
If you're drawing 70amp/hrs in a day, you'll need ten times that (700amp/hrs), minimum battery bank size, as you shouldn't aim to take more than 10% out in a day! This isn't me trying to flog you lots of batteries - it is a pragmatic "rule of thumb" to ensure reasonable and economic battery life and performance!

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Amateurs encouraged - very keen prices and friendly helpful service!