Thanks for all the good info that I have received here.

Based on the info here, I have a feeling that the auther of the boat
recommended the use of dual purpose batteries for a center console has
to do with this reason:

- The author didn't expect the use of a trolling motor in a center
console, and a center console tends not to have anything like a
refrigrator that uses a lot of amps. Therefore, he didn't think a
center console needs any deep cycle battery; then he could save money
and weight. This leaves the choice between starting batteries or dual
purpose batteries. At this point, I don't know why he didn't simply
suggest the use of one starting battery and one dual purpose battery
instead of two dual purpose batteries; he suggested the use of starting
batteries in other types of boats anyway; I don't see why he didn't
suggest the use of a starting battery in a center console. This seems
to be an inconsistence in his recommendation. May be he was trying to
simplify his recommendation; therefore, he said something simple like
this:
"For a center console, I recommend using two dual purpose
batteries."
instead of saying something complicated like this:
"For a center console, I recommend using two dual purpose
batteries or one starting battery and one dual purpose battery."

Based on the info that I have received here and the recommendation from
the book, I can say these:

- If I intend to use minimum electronic devices in a center console,
I can follow the "two dual purpose batteries" approach.

- If I intend to use a small number electronic devices (such as a
radio and a fishfinder) plus a 12-volt trolling motor in a center
console, I should use two deep cycle batteries and one of them must
have enough cranking power rating (CCA rating).

- If I intend to use a small number electronic devices plus a 12-volt
trolling motor in a center console, but the motor is the kind that I
need to crank a couple times before it can start, I should use two deep
cycle batteries and _both_ of them must have enough cranking power
rating (CCA rating). Am I understand this point correctly? Should I
use a combination of one dual purpose battery and one high CCA deep
cycle battery?

Seem like the question is "What kind of batteries should I use if the
motor is the kind that I need to crank a couple times"? No, the motor
in my boat is not like that. I am asking this just for educational
purpose.

Jay Chan


wrote:
I am reading a book called "Powerboater's Guide to Electronic Systems".
The book recommends using two dual-purpose batteries if the boat is a
center console. A dual purpose battery is supposed to be good for both
cranking the motor and serving as a house battery. I am wondering why
a dual purpose battery is the best kind for a center console, but not
the best for a cruising boat (he recommended a combination of a
starting battery and a deep cycle battery for a cruising boat). What
are the reasoning behind this? Won't a combination of a starting
battery and a separated deep cycle battery is just as good for a center
console?

My center console is having two dual-purpose batteries just like what
the book has recommended. I guess this is good. I just don't know why
this is good.

Thanks in advance for any info.

Jay Chan