Deep cycle and cranking battery question

It seems that most agree a deep cycle bat is best for the house and a cranking bat for cranking. It seems like most also agree that when the battery switch is moved to 1&2, the batteries instantly equalize. My question is wouldn't that make the cranking battery experience substantial cycling? I realize it wouldn't be going from 100% to 0% and back like the house bat might but isn't 100% to 50% more of a cycle than a cranking bat is expected to handle? If a deep cycle has plenty of cranking amps to crank the engine, could it be better to use deep cycles only?

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Originally Posted by Stillski

It seems that most agree a deep cycle bat is best for the house and a cranking bat for cranking. It seems like most also agree that when the battery switch is moved to 1&2, the batteries instantly equalize. My question is wouldn't that make the cranking battery experience substantial cycling? I realize it wouldn't be going from 100% to 0% and back like the house bat might but isn't 100% to 50% more of a cycle than a cranking bat is expected to handle? If a deep cycle has plenty of cranking amps to crank the engine, could it be better to use deep cycles only?

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I ran my boat almost entirely on the deep cycle for the last several years. The other (starting) battery was basically a backup, charged by my solar trickle charger. Also both batteries lasted 7 seasons in my boat with this system, and both still have some life, although I will probably replace both this season on principle.

I can't say anything about the science here, but it's one anecdotal data point...

Thanks for the reply, I've read a lot on the subject but never anything on whether the equalizing cylces the starting battery more than it's made for. I guess I'm going to go with the conventional deep cycle/starting combo as most do. Besides, with this boat I don't think I'll be hanging out at the beach nearly as much as we used too!