@CrazyOldMan
Yes, Deep cycle batteries are preferred. No need for a starter battery or dual purpose battery.
The link
@Hello Below posted describes the difference in the three types of batteries.
So why are deep cycle batteries preferred for starting by many?
While you can use a starter battery for starting the small diesels in our sailboats, using a starter battery for house loads and only charging it occasionally will shorten the life of the starter battery.
Using a deep cycle battery for starting gives us a good reserve battery so that battery can also be used for house loads without shortening it's life.
Here is an excerpt from a post by Maine Sail, a member of this forum who is a marine electrician.
"Batteries calendar age too and are murdered much more rapidly by heat than folks often assume. I've seen no
real world evidence that a battery used as reserve only lives a measurably longer life than one used for starting only. When wired properly both last a good long while. I have
many dedicated starting batteries (
usually "deep cycle" on sailboats) that last 6-12 years or more where the house/cycling bank has been replaced one, two or three times. When
cheap auto-type starting batteries are used for starting or reserve applications the
average life I see is about
3-7 years regardless of starting or reserve use. Whether used as a dedicated starting or reserve battery really seems to make little difference in longevity though battery type does."
If you normally start your diesel with your house bank then you should have a true deep cycle and rename this single battery from starting.battery to a reserve battery.
This is becoming the preferred way to think of and use your two battery banks. If you draw down the house bank too low to start the diesel or it otherwise fails in some way, you just switch to the reserve and use that for house loads and starting until the house bank is back up to normal.
Hope that answers your question.
