[C320-list] Inadequate Dedicated Starting Battery

[Onat Dogruer]

Hi Bob,

I tend to be very cautious before commenting without knowing how things are
wired on someone's boat. However, the issue doesn't sound like a wire gauge
issue. Typically older diesels have a higher cranking amp requirement,
recommended 450-500CCA min starting battery. Our 1998 has a Yanmar 3GM30F
and starting surge is 283A.  The start surge is only for a second or two
and once the engine kicks up, alternator starts feeding back. Our setup is
slightly similar; we have deep cycle golf cart batteries but we always
start on that bank. Aux battery serves as an emergency start.

G27 batteries should be more than adequate; even a good G24 will suffice.
The issue might be the 'new' battery may not actually be in good
condition.
Alternatively, there may be a loose terminal (even a slight wobble will
decrease output).  If I were facing this, I would start by the simplest and
check the terminals, go over the wiring of the house bank and of the
starting battery, and lastly may do a load-test on the starting battery.



On Tue, Dec 7, 2021 at 8:54 AM Bob Hoyt <rehoyt at gmail.com> wrote:

> I recently installed a Duralast G27 Marine battery to serve as a dedicated
> starting battery to go with my house batteries (4 six-volt golf cart
> batteries in series). I installed it just forward of the starboard battery
> compartment. The existing cables are listed as 4 gauge, so I thought they
> were adequate.
> With a fully charged new battery and either a cold or warm engine, the
> motor will barely turn over. With the battery selector on all, it starts
> quickly. Is the group 27 battery underpowered or do I need to change the
> wire from the battery to the main switch and wire from the switch to the
> starter motor to 2 gauge? Thanks
>
> Bob Hoyt
> Hull 154
> 1994 C320 "Ikigai"
> Pensacola, Fl
>
>
> --
>
> *Robert (Bob) Hoyt MD, FACP, FAMIA, ABPM-CI*
>
> *Associate Clinical Professor, Department of Internal Medicine*
>
> *Virginia Commonwealth University*
>
> *Richmond, VA*
>
>
> *CAPT (Ret) USN*
>
> InformaticsEducation.org  <http://InformaticsEducation.org>
> rehoyt at gmail.com
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>