I was talking to an engineer with a local school bus manufacturer yesterday
about Rutu's progress. I mentioned that I was leaning towards a high
capacity Group 31 battery to use for the starter bank. More than the 4JH4
needs but would give me a lot of reserve. He replied that was a bad idea
on a sailboat. Seems that they no longer equip their school busses with 925
CCA Group 31's because they have a very high self discharge rate. They are
great for regular highway use but school busses like sailboats spend a lot
of time with the engine off. The 620 to 700 CCA batteries hold their charge
much better and will last a lot longer in that type service.

Just another tidbit to store away for future use.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Glenn Ashmore wrote:
I was talking to an engineer with a local school bus manufacturer yesterday
about Rutu's progress. I mentioned that I was leaning towards a high
capacity Group 31 battery to use for the starter bank. More than the 4JH4
needs but would give me a lot of reserve. He replied that was a bad idea
on a sailboat. Seems that they no longer equip their school busses with 925
CCA Group 31's because they have a very high self discharge rate. They are
great for regular highway use but school busses like sailboats spend a lot
of time with the engine off. The 620 to 700 CCA batteries hold their charge
much better and will last a lot longer in that type service.

Just another tidbit to store away for future use.

I've used AGM's for my starting batteries. The self discharge is very
low, and the cost isn't that high.

Glenn Ashmore wrote:
I was talking to an engineer with a local school bus manufacturer
yesterday about Rutu's progress. I mentioned that I was leaning
towards a high capacity Group 31 battery to use for the starter bank.
More than the 4JH4 needs but would give me a lot of reserve. He
replied that was a bad idea on a sailboat. Seems that they no longer
equip their school busses with 925 CCA Group 31's because they have a
very high self discharge rate. They are great for regular highway use
but school busses like sailboats spend a lot of time with the engine
off. The 620 to 700 CCA batteries hold their charge much better and
will last a lot longer in that type service.

Just another tidbit to store away for future use.

Glenn, thanks for the info. I targeted Gr-31s as my battery
because they are cheap & readily available... the last bunch
I bought were no-maintenance types from the 'Batteries Plus'
outlet, re-labelled Exides.


Jeff wrote:
I've used AGM's for my starting batteries. The self discharge is very
low, and the cost isn't that high.


I haven't found AGMs for less than about twice the price of
'dual-purpose' Gr-31s, which are about $60 at the
farm-n-truck supply.

OTOH I'm surprised Glenn isn't buying Surrette batteries for
his boat.

Fresh Breezes- Doug King

Someone help me out here. I always thought that the Group number just
specified the size/shape of the battery. Why would thhe size or capcity
affect its ability to hold a charge? Are you talking about a specific
manufacturer's battery? I can see how one manufactures group 31 my not, but
Group 31's in general?


"Glenn Ashmore" wrote in message
news:eC4Ef.15932$Dh.8853@dukeread04...
I was talking to an engineer with a local school bus manufacturer yesterday
about Rutu's progress. I mentioned that I was leaning towards a high
capacity Group 31 battery to use for the starter bank. More than the 4JH4
needs but would give me a lot of reserve. He replied that was a bad idea
on a sailboat. Seems that they no longer equip their school busses with
925 CCA Group 31's because they have a very high self discharge rate. They
are great for regular highway use but school busses like sailboats spend a
lot of time with the engine off. The 620 to 700 CCA batteries hold their
charge much better and will last a lot longer in that type service.

Just another tidbit to store away for future use.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

On Wed, 01 Feb 2006 13:03:26 -0500, DSK wrote:

OTOH I'm surprised Glenn isn't buying Surrette batteries for
his boat.

Surrette and Rolls both make great batteries, no question about that.

I'm certainly curious as to why Group 31s would have a higher self
discharge rate than others. I've never heard that before and wonder
if it could possibly have been related to a specific manufacturer or a
bad batch. Any boat left unattended should have some means of keeping
the batteries topped off in my opinion.

On my old boat I used golf cart batts for everything, never had a
problem, even starting up cold 454s. My new boat is set up for 8D
starting batts and I've left it that way but added 8 golf carts in two
separate house banks.

It is not all Group 31 batteries. Just the high capacity 925 CCA type.

Here is the service bulletin they got from their chassis supplier:
http://www.internationaldelivers.com...pdf/dyk128.pdf

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"johnhh" wrote in message
...
Someone help me out here. I always thought that the Group number just
specified the size/shape of the battery. Why would thhe size or capcity
affect its ability to hold a charge? Are you talking about a specific
manufacturer's battery? I can see how one manufactures group 31 my not,
but Group 31's in general?


"Glenn Ashmore" wrote in message
news:eC4Ef.15932$Dh.8853@dukeread04...
I was talking to an engineer with a local school bus manufacturer
yesterday about Rutu's progress. I mentioned that I was leaning towards a
high capacity Group 31 battery to use for the starter bank. More than the
4JH4 needs but would give me a lot of reserve. He replied that was a bad
idea on a sailboat. Seems that they no longer equip their school busses
with 925 CCA Group 31's because they have a very high self discharge rate.
They are great for regular highway use but school busses like sailboats
spend a lot of time with the engine off. The 620 to 700 CCA batteries
hold their charge much better and will last a lot longer in that type
service.

Just another tidbit to store away for future use.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

OTOH I'm surprised Glenn isn't buying Surrette batteries for his boat.

You just gotta draw the line somewhere. Besides the Trojan distributor here
in town rents his warehouse from me. :-)

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

DSK wrote:
....


Jeff wrote:

I've used AGM's for my starting batteries. The self discharge is very
low, and the cost isn't that high.


I haven't found AGMs for less than about twice the price of
'dual-purpose' Gr-31s, which are about $60 at the farm-n-truck supply.

I found Optima's at an auto shop (PEP? Autozone?) for about $100.
We'll find out in about 3 years if they do better than the el cheapo's
they replaced.


OTOH I'm surprised Glenn isn't buying Surrette batteries for his boat.

I was in my marina office asking if they could match they price I had
for 4 Trojan 105 6 Volts ($280 from a golf cart company). They could
come close using AC Delco, but not Trojan. Just then, the Surrette
distributor walked in and started explaining to me that while Trojan's
were very good, they weren't the same as Surrette's. Since the
Surrette's cost about $800 for the set, I figured that paying a third
for a bank that's almost as good was a deal. The previous Trojans had
lasted 6 hard seasons, so I didn't think Surrettes would be much
better. OTOH, the Surrettes that came with my previous boat lasted 12
years, so it might be a tossup.

Hello Glenn,

I am also skeptical. Couldn't find out what the CT-400 is or who wrote
it or why, but the idea that someone would make a high-capacity Group 31
battery and then recommend it only for frequent charging use sounds
almost counter-intuitive.

After a very quick check of Exide's battery application guide, it
appears that their only Group 31, 925 cca battery carries a 24-month
warranty! Talk about disposable.

They have other Group 31's with lower cca ratings carrying the same
warranty, and they also have Group 31's with lower cca ratings carrying
six and seven year warranties.

But it is probably a true statement that all of the Exide Group 31's
rated at 925 cca will not last long, for whatever reason.

A similar statement could not be made about ALL of the Exide Group 31's
with lower 925 cca ratings.

Make sense? Sounds like it might be coincidence.

Chuck

Glenn Ashmore wrote:
It is not all Group 31 batteries. Just the high capacity 925 CCA type.

Here is the service bulletin they got from their chassis supplier:
http://www.internationaldelivers.com...pdf/dyk128.pdf

I think what the bus company is saying about the batteries makes
perfect sense. You get CCA, the ability to put out a lot of power in a
short period, by having more plate surface area. The only way to get
more surface area in the same box size is to have more plates. More
plates will be thinner and less rugged. Reducing the space between
the plates also makes the changes in shape that is inevitable with
deep charging cycles more likely to cause plates to touch.

Self discharge should be primarily a function of surface area as that
is where the reactions take place. More surface area for more fast
output capacity has got to be a trade off for self discharge rate.
The only way to avoid these trade offs is to increase the size of the
box which is effectively what they are recommending when they suggest
increasing the number of batteries.

--

Roger Long



"chuck" wrote in message
link.net...
Hello Glenn,

I am also skeptical. Couldn't find out what the CT-400 is or who
wrote it or why, but the idea that someone would make a
high-capacity Group 31 battery and then recommend it only for
frequent charging use sounds almost counter-intuitive.

After a very quick check of Exide's battery application guide, it
appears that their only Group 31, 925 cca battery carries a 24-month
warranty! Talk about disposable.

They have other Group 31's with lower cca ratings carrying the same
warranty, and they also have Group 31's with lower cca ratings
carrying six and seven year warranties.

But it is probably a true statement that all of the Exide Group 31's
rated at 925 cca will not last long, for whatever reason.

A similar statement could not be made about ALL of the Exide Group
31's with lower 925 cca ratings.

Make sense? Sounds like it might be coincidence.

Chuck

Glenn Ashmore wrote:
It is not all Group 31 batteries. Just the high capacity 925 CCA
type.

Here is the service bulletin they got from their chassis supplier:
http://www.internationaldelivers.com...pdf/dyk128.pdf