BoatBanter.com - View Single Post - Why Are Dual Purpose Batteries the Best for Center Console Boats?

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

Sounds like the "Powerboater's Guide to Electronic Systems" wasn't
written by a powerboater.

You've got some bad advice.

There is almost no earthly reason to ever have a "starting battery" on
a boat, except it will help the battery manufacturer sell a greater
number of batteries each year. Starting batteries have lighter weight
(thinner) plates so additional surface area can be exposed to the
electrolyte and maximize the CCA rating in a given case size. Those
thin plates disintegrate faster than the thicker plates in a "deep
cycle" battery, and when one plate is gone the battery is toast. The
thin plates make it bad practice to discharge a starting battery very
deeply- the recharge stresses the thin plates and leads to premature
battery failure.

(I use Rolls batteries on my boat. They are sold with a 10-year
warranty. Rolls doesn't even offer a "starting battery", and the
Rolls/Surette company is one of the premiere manufacturers of flooded
cell batteries.)

If space is so tight that you just can't possibly fit a deep cycle
battery rated for sufficient CCA, then I suppose a "starting" battery
must be used- but that situation will arise once in a couple of hundred
installations. In fact, if space is *that* tight, you battery
compartment is probably inadequately ventilated and you have some
other, potentially more serious problems.

Best plan: Always use a deep cycle battery for house loads. Use a deep
cycle battery with sufficient CCA to start your engine in nearly all
applications. Have at least two batteries, properly cabled and
switched.