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

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

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

"Roger Long" wrote in news:wRbEf.1929$5Q3.852
@twister.nyroc.rr.com:

deep charging cycles more likely to cause plates to touch.



I can tell this is gonna be a LONG thread....(c;

Sounds like I got something wrong. Please explain.

As I understand it, metal physically moves from the plates into
solution as the batteries discharge and back as they charge. Since it
doesn't redeposit perfectly, the plates become lumpy. The greater the
discharge, the greater this effect. Lower clearance between the
plates make the battery less tolerant.

Batteries are far from the center of my expertise so I'm not
embarrassed to be wrong. What am I missing here?

--

Roger Long



"Larry" wrote in message
...
"Roger Long" wrote in news:wRbEf.1929$5Q3.852
@twister.nyroc.rr.com:

deep charging cycles more likely to cause plates to touch.



I can tell this is gonna be a LONG thread....(c;

"Roger Long" wrote in news:ZTlEf.6124$bU6.389
@twister.nyroc.rr.com:

As I understand it, metal physically moves from the plates into
solution as the batteries discharge and back as they charge. Since it
doesn't redeposit perfectly, the plates become lumpy. The greater the
discharge, the greater this effect. Lower clearance between the
plates make the battery less tolerant.

The plates never move...er, ah...we hope! They certainly don't want to
touch each other or the battery EXPLODES, almost instantly. Lead acid
batteries are very dangerous beasts. Boiling acid from the immense
current passing through the acid, turns to steam very quickly and just
blows the case apart, spreading acid steam throughout the boat and
corroding even the spoons inside the drawers in the galley. Seen that.

The chemistry isn't rocket science. The soft lead is eaten away and
converted into lead sulphate, in solution we hope in the electrolyte.
These ions are fairly stable in the electrolyte so we can recover them
later during charging. The conversion releases an amazing amount of
electrons at a little over 2V potential very quickly, making it a great
starting battery where we need lots of current for a short time. By
applying an external potential force, the charger, we can reverse this
chemical reaction, electrically, and recover most, but not all, of the
ions. Some ions attached themselves to each other forming a crystal of
lead sulphate which is VERY stable and, now a solid, falls out of the
electrolyte into a special cavity under the plates, out of the way. In
AGM batteries, this isn't possible, so I suppose tiny areas of the huge
surface area of the wrapped up plates simply become inert.

The plates are held apart, because lead is so soft, by insulating
separators that are a grid of several materials acid doesn't attack.
This holds the plates firmly for moving vehicles. AGM batteries are held
in place by the guaze, which performs the same exact function...allow the
acid soaked up in the gauze to attack the plates, while holding the
plates apart to prevent shorting. AGM isn't as magic as its marketing
hype. It's still a 50-year-old lead-acid battery manufactured in a
different way to reduce maintenance and volume and production costs.

Batteries are far from the center of my expertise so I'm not
embarrassed to be wrong. What am I missing here?


Don't be embarrassed at all, Roger. The combined knowledge of hulls of
everyone else on this forum is probably less than 5% of your knowledge of
the subject. We all have our specialties in modern society. You make
the hulls more efficient and faster and let us argue over the
batteries...(c;

This argument over ancient battery technology will soon be moot. Toshiba
has used nanotube technology to invent a new Lithium-Ion battery that
charges from dead to 80% of its capacity in SIXTY SECONDS and a full 100%
charge in less than 3 minutes....while amazingly losing less than 1% of
its original capacity (AH rating) in 1000 charge-discharge cycles. This
technology may make hybrid and electric cars a reality in our lifetimes.
We've never been able to charge any battery fast enough. This battery
has solved the problem. You press on the dynamic braking pedal and the
big traction motors driving the wheels charge the hell out of the new
batteries in the trunk, recovering most of the energy wasted in brake
pads on your car so we can use it again and again to drive the car.
Electric cars will plug into huge conductors at charging stations to
charge at hundreds of amperes while you're inside buying a drink and
paying the attendant for the power....in less than 3 minutes.

Instead of running the diesel for hours to recharge the house batteries
from 1% of its wasted power just waiting for lead and acid to replate the
lead plates, the new battery will charge at the full output hp the diesel
can produce, the new battery now waiting for the engine, not the other
way around. Diesel-electric propulsion will also use the prop's traction
motors as generators to recharge the batteries with every available hp
under sail....

http://www.physorg.com/news3539.html

http://freeenergynews.com/Directory/Battery/index.html

MIT is working on a nanotube supercapacitor to store energy instantly.
They think possibilities of 100kW/kg is possible, three times what the
batteries can store in the same load! Here's the link:
http://lees.mit.edu/lees/projects/cn...ap_project.htm
Its life will be over 300,000 cycles....never needing replacement??
A better pdf is from the website:
http://lees.mit.edu/lees/posters/RU13_signorelli.pdf
This nanotube capacitor isn't chemical AT ALL...No chemical reaction
takes place....purely electrical in nature, storing the charging
electrons over a massive nanotube surface area in a very tiny space.

Fuji and Mitsubishi are already in full research:
http://www.worldchanging.com/archives/003339.html
You plug it in for 5 minutes, it runs 75 miles at 50. They're working to
expand this to 124 miles, soon. All in 5 minutes charging....at great
power.

"johnhh" wrote in
:

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?


They use special "Group 31 lead" that wasn't minted at the Franklin Mint
like Surette battery lead all is. They also use "ordinary acid", not that
special blend of highly purified, laboratory-grade, .99976% fine the $400
battery makers all use made in tiny batches by the same chemists that
invented Amsoil oils and insecticides. Obviously, the combination of
"Group 31 Lead" and ordinary acid in the cheap ordinary plastic case is
inferior to the $400 batteries only sold at fine marine chandleries like
Waste Marine, Boater's World and Doug's Marina and Tire....

Besides....Group 31 batteries all come in ugly black plastic, not those
pretty maroon or red cases that increase CCA and AH by over 40% when placed
in a fine yacht like a Bayliner or Sea Ray....

Larry wrote:
snip when placed in a fine yacht like a Bayliner or Sea Ray....

fine yachts indeed!
Recently I found out that there are actually 3 types of yachts cruising
the Great Lakes. Sitting in the cockpit of our sailboat soaking up some
sun and suds the following enlightening exhange was overheard on ch. 68
in the Killarney Channel.

"Sportsman's, Sportsman's, Sportsman's, this is the Lotsa Lettuce, Lotsa
Lettuce, Lotsa Lettuce over..."

"Lotsa Lettuce...this is Sportsman's good day sir"

"Ah yeah we've got a reservation and blah blah blah"

"Roger that sir, please say your length and type."

and in the stentorial tones summoned only by the likes of proprietors of
only the finest of fine yachts and perhaps Ted Baxter we heard in response

"Roger that, ahem, we're a 53 foot -insert dramatic pause here- Searay"

Well you can imagine what a revelation this was for us. As I was in the
middle of a rather largish gulp of the golden brew, my sinuses were
treated to an involuntary high-pressure beer rinse as the import of this
pronouncement washed over me. 3 types??!? Sail, power....and Searay?
My God! who knew???

prodigal1 wrote in :

"Roger that, ahem, we're a 53 foot -insert dramatic pause here- Searay"



Hmm...maybe he was trying to warn the dockhands that he was driving a big
boat made of putty so they'd be very careful not to bump it into the dock,
which may destroy it, unlike real fiberglass boats.

http://yachtsurvey.com/Fiberglass_Boats.htm

I can understand his wanting to warn them he was driving a Sea Bayliner....
(c;