Is there any reason to consider using dual purpose or a one starting, one deep cycle set up with a 20 hp Yanmar diesel? I would think the starting loads on the small engine are low enough that two deep cycle batteries would do fine.

--

Roger Long

I suspect that you are correct. Our boat came equipped with 2 8D house batteries
and a 4D starting battery. The starting battery was actually a deep cycle gel
cell and worked perfectly well. (85 HP Perkins) I replaced it with a Group 30
starting battery for the savings in size. Unless your engine is hard to start and
requires alot of cranking Incidently, the previous owner accidently started the
engine in -20F temps using the deep cycle battery!


Doug
s/v CAllista

"Roger Long" wrote in message ...
Is there any reason to consider using dual purpose or a one starting, one deep cycle set up with a 20 hp Yanmar diesel? I would think the starting loads on the small engine are low enough that two deep cycle batteries would do fine.

--

Roger Long

I agree with Doug.

i don't see any problems with it.

Roger Long wrote:
Is there any reason to consider using dual purpose or a one starting,
one deep cycle set up with a 20 hp Yanmar diesel? I would think the
starting loads on the small engine are low enough that two deep cycle
batteries would do fine.

--

Roger Long



No problem - my Yanmar 2gm20's start almost instantly, and there's no
pre-heater, so the load is modest (80 Amps?) and the total drain is
minimal. However, I took the opportunity to replace my starter deep
cycles with zero hassle AGM cranking batteries.

Roger:

Yes, two deep cycle batteries should easily start a two cylinder Yanmar. But don't you want to separate the batteries so you can't run them both down at the same time? I am pretty sure that one deep cycle Group 27 will also start your Yanmar easily. So set up two deep cycle batteries; each on one side of a 1, 2, all, off switch so you can always have one battery fully topped off after sailing all day after using the house loads. You can then alternate your "house" and "starting" batteries to keep them equally charged up.

David
"Roger Long" wrote in message ...
Is there any reason to consider using dual purpose or a one starting, one deep cycle set up with a 20 hp Yanmar diesel? I would think the starting loads on the small engine are low enough that two deep cycle batteries would do fine.

--

Roger Long

Yes, a deep cycle will start your Yanmar, but you are reducing the
life of the battery by doing so.

There's a reason, other than marketing, why batteries are labeled
'starting' or 'deep cycle' or 'dual purpose'.
I believe the main difference is the thickness of the plates. Starter
batts, are built for short duration, high loads. DC are for less
load over a longer time period. DP are a compromise between the two.


--
Scott Vernon
Plowville Pa _/)__/)_/)_


"Roger Long" wrote in message
...
Is there any reason to consider using dual purpose or a one starting,
one deep cycle set up with a 20 hp Yanmar diesel? I would think the
starting loads on the small engine are low enough that two deep cycle
batteries would do fine.

--

Roger Long

I understand that but, is the load on a 20 hp diesel that you can
start by hand high enough to significantly reduce the life of the
battery?

--

Roger Long



"Scott Vernon" wrote in message
...
Yes, a deep cycle will start your Yanmar, but you are reducing the
life of the battery by doing so.

There's a reason, other than marketing, why batteries are labeled
'starting' or 'deep cycle' or 'dual purpose'.
I believe the main difference is the thickness of the plates.
Starter
batts, are built for short duration, high loads. DC are for less
load over a longer time period. DP are a compromise between the two.


--
Scott Vernon
Plowville Pa _/)__/)_/)_


"Roger Long" wrote in message
...
Is there any reason to consider using dual purpose or a one
starting,
one deep cycle set up with a 20 hp Yanmar diesel? I would think the
starting loads on the small engine are low enough that two deep
cycle
batteries would do fine.

--

Roger Long

I understand that but, is the load on a 20 hp diesel that you can start by
hand high enough to significantly reduce the life of the battery?

It depends on what you're using your boat for. If you're starting &
stopping your engine frequently, then maybe a starter battery makes sense.
But while cruising and using my 3GM30 (actually 27 hp) all I used were deep
cycles and they worked fine.

Another topic, one maybe you've thought about already, is how well the
alternator on your Yanmar is charging your batteries. If your charging
system isn't up to snuff, doesn't matter what batteries you're using, you'll
never get full cranking amps out of your batteries.

Paul

Define 'significantly'. If you're starting only once in a while, as
most sailboats do, I doubt that you'll notice the shortened life.
Are you buying new batts, or are there 2 DC already in your boat?

I had the separate start batt and a DC, When the DC went , I replaced
with a DP (that's all the local Sears stocks anymore). When the
starter batt goes away, I'll go with a second DP. I have a manual
separator switch.


--
Scott Vernon
Plowville Pa _/)__/)_/)_


"Roger Long" wrote in message
...
I understand that but, is the load on a 20 hp diesel that you can
start by hand high enough to significantly reduce the life of the
battery?

--

Roger Long



"Scott Vernon" wrote in message
...
Yes, a deep cycle will start your Yanmar, but you are reducing the
life of the battery by doing so.

There's a reason, other than marketing, why batteries are labeled
'starting' or 'deep cycle' or 'dual purpose'.
I believe the main difference is the thickness of the plates.
Starter
batts, are built for short duration, high loads. DC are for less
load over a longer time period. DP are a compromise between the
two.


--
Scott Vernon
Plowville Pa _/)__/)_/)_


"Roger Long" wrote in message
...
Is there any reason to consider using dual purpose or a one
starting,
one deep cycle set up with a 20 hp Yanmar diesel? I would think
the
starting loads on the small engine are low enough that two deep
cycle
batteries would do fine.

--

Roger Long

Roger Long wrote:
I understand that but, is the load on a 20 hp diesel that you can
start by hand high enough to significantly reduce the life of the
battery?


What's the voltage drop when starting? Starting batteries can see surges
bring them down to as low as 8 volts and bounce back just fine. DC
batteries don't like this.

I'm not sure where the cut-off is, but if the starting load drops your
voltage down below 10, or maybe 10.5 (assuming that you've got a good
current path to starter & ground), then you might consider staying with
a start battery.

Fresh Breezes- Doug King