"Doug Dotson" dougdotson@NOSPAMcablespeedNOSPAMcom wrote in
:

One big house bank and a separate starting battery is best for a number
o reasons.



Any idea why?

--
Larry

On Sat, 20 Aug 2005 08:38:41 -0400, Larry wrote:

"Doug Dotson" dougdotson@NOSPAMcablespeedNOSPAMcom wrote in
:

One big house bank and a separate starting battery is best for a number
o reasons.



Any idea why?

http://www.vonwentzel.net/Battery/03.Banks/index.html

"Some things to keep in mind:

The only caveat to large banks of batteries is proper internal fusing.
If a cell shorts out in a battery, the battery voltage will drop
approximately 2 Volts. All batteries in the bank will start
discharging into the shorted battery, unless fuses take the bad
battery out of the circuit. Thus, battery banks need to be fused
internally as well as externally."

--
Larry

"Mic" wrote in message
...
On Sat, 20 Aug 2005 08:38:41 -0400, Larry wrote:

"Doug Dotson" dougdotson@NOSPAMcablespeedNOSPAMcom wrote in
:

One big house bank and a separate starting battery is best for a number
o reasons.



Any idea why?

http://www.vonwentzel.net/Battery/03.Banks/index.html

"Some things to keep in mind:

The only caveat to large banks of batteries is proper internal fusing.
If a cell shorts out in a battery, the battery voltage will drop
approximately 2 Volts. All batteries in the bank will start
discharging into the shorted battery, unless fuses take the bad
battery out of the circuit. Thus, battery banks need to be fused
internally as well as externally."

--
Larry

Good point, but a fuse will not neccessarirly mitigate a failure of this
sort.

(Mic) wrote in :

The only caveat to large banks of batteries is proper internal fusing.
If a cell shorts out in a battery, the battery voltage will drop
approximately 2 Volts. All batteries in the bank will start
discharging into the shorted battery, unless fuses take the bad
battery out of the circuit. Thus, battery banks need to be fused
internally as well as externally."


If a cell shorts out in a battery, the cell explodes boiling its
electrolyte into steam, damn near instantly, unless it's already dead. The
other cells in SERIES with the dead cell have no current through it. The
other batteries may explode if not properly fused, even if the other good
cells in the blown battery oppose them, overcharging like mad in the
process. All batteries MUST BE FUSED! I like about 150% of the starter
current and the wiring must be able to handle that current level to blow
the fuse....not the crap house wiring I see on house batteries all the
time.

There's no way I know of to keep the shorted cell from exploding,
distributing its acid over everthing in every drawer in the boat....what a
mess.



--
Larry

Larry wrote:
....

There's no way I know of to keep the shorted cell from exploding,
distributing its acid over everthing in every drawer in the boat....what a
mess.

My batteries are on the bridge deck in the cockpit, with a heavy
fiberglass cover. Reaching the cabin or bilge would require going
through a major bulkhead.

Of course, I wouldn't want to be sitting on the cover at the time ...

On Sat, 20 Aug 2005 16:12:46 -0400, Larry wrote:

(Mic) wrote in :

The only caveat to large banks of batteries is proper internal fusing.
If a cell shorts out in a battery, the battery voltage will drop
approximately 2 Volts. All batteries in the bank will start
discharging into the shorted battery, unless fuses take the bad
battery out of the circuit. Thus, battery banks need to be fused
internally as well as externally."


If a cell shorts out in a battery, the cell explodes boiling its
electrolyte into steam, damn near instantly, unless it's already dead. The
other cells in SERIES with the dead cell have no current through it. The
other batteries may explode if not properly fused, even if the other good
cells in the blown battery oppose them, overcharging like mad in the
process. All batteries MUST BE FUSED! I like about 150% of the starter
current and the wiring must be able to handle that current level to blow
the fuse....not the crap house wiring I see on house batteries all the
time.

There's no way I know of to keep the shorted cell from exploding,
distributing its acid over everthing in every drawer in the boat....what a
mess.

I had a cell in one of two parallelled 4D batteries develop a short,
without exploding, or any other serious consequences.

I noticed while cruising that I was unable to get my batteries above
13 volts or so, despite using a 40 amp charger for 24 hours - but I
was still able to start the engine and run all accessories.

After the cruise, I was checking battery water, and found that one
battery required lots of water in all but one cell, while the other
didn't need any. Switching to the thirsty battery only, I was unable
to start the engine, and the voltage on that battery was only 10 volts
or so, while the other was over 12.

I expect that the "shorted" cell was really a low resistance, rather
than a zero-ohm short.

I've since replaced the 4Ds with 4 Golf Carts as a house bank, and a
Group 27 for starting. I don't have fuses on the two series pairs of
GCs, but do have a 1-both-2 switch so I can easily test each series
pair independently.

A problem I see with fusing sections of a battery bank is selecting a
fuse rating high enough that it won't blow when starting, or running
the bow thruster, but low enough that it will blow on a fault.



--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

"Larry" wrote in message
...
(Mic) wrote in :

The only caveat to large banks of batteries is proper internal fusing.
If a cell shorts out in a battery, the battery voltage will drop
approximately 2 Volts. All batteries in the bank will start
discharging into the shorted battery, unless fuses take the bad
battery out of the circuit. Thus, battery banks need to be fused
internally as well as externally."


If a cell shorts out in a battery, the cell explodes boiling its
electrolyte into steam, damn near instantly, unless it's already dead.
The
other cells in SERIES with the dead cell have no current through it. The
other batteries may explode if not properly fused, even if the other good
cells in the blown battery oppose them, overcharging like mad in the
process. All batteries MUST BE FUSED!

Nobody sugggested that fusing isn;t necessary. Just that is does not
necessarily protect against a shorted cell. I had a cell short once and
all it did was lower the voltage of the battery and discharge the parallel
battery. No dramatic event, just dead batteries.

I like about 150% of the starter
current and the wiring must be able to handle that current level to blow
the fuse....not the crap house wiring I see on house batteries all the
time.

There's no way I know of to keep the shorted cell from exploding,
distributing its acid over everthing in every drawer in the boat....what a
mess.



--
Larry

(Mic) wrote in :


" The Preferred System

The Preferred System consists of a single house bank, and a dedicated
starter battery for all engines. A separate generator battery is
sometimes present. "

I disagree....

"......a two house bank system is no longer necessary. In fact, the
more battery banks in use, the less reliable the system will be, while
also increasing cost and management problems."

Ol' Nigel, the expert just because he has a publisher, must have a pretty
large boat. If he does, then he can have one huge house battery. But,
real boaters don't have that luxury. The batteries go where they can. One
house bank means a 130AH deepcycle or two 230AH golf cart batteries in
series because there's just no place to put them. This isn't enough power
if you have radio/radar/autopilot/refridgerator/pumps/computer and lights
running 24/7 at sea. Then, what happens if a cell shorts or opens or just
decays? Is ol Nigel gonna run it off the starting battery? I think NOT.
He's gonna sit in the dark while we go on with our redundant system of TWO
house battery banks, only concerned with a little conservation.

NASA has at least two, if not 4 to 8, of everything aboard any spacecraft.
A ship is a spacecraft...stranded in its environment with no hope of
repairs...it still needs redundancy. Even two sets of 130AH deep cycles,
which now require no maintenance, is better than one set of golf cart
batteries, which do. Nobody in a boat has too much power...especially sail

"Instead of a 1-2-both switch, a simple parallel switch can be used to
start the engine from the house bank if needed. "

Unless, of course, your NOT at the dock out there in the 8' waves where you
can't work to disconnect the shorted starting battery being beaten to death
by the sea. I use a simple paralleling switch in my stepvan because if I
have to I can stop, get out, and fix whatever's wrong. A 33' sloop in 8'
seas doesn't have that luxury, what with everyone hanging on for dear life
rockin' and rollin' just trying to keep her pointed home. A simple switch
paralleling the two banks on a shorted starting battery will simply short
the whole house. It isn't going to start.


"But, if you make the house bank from parallel batteries a cell
failure in one only knocks out that battery."

See? He answers my problem in the paragraph above. This is why Lionheart
has TWO 1-2-Both battery switches. One switch selects which house battery
powers the house. The other battery switch selects whether the house or
the starting battery starts the Perkins. If you put both switches in BOTH,
they all crank the Perkins and power the house. REDUNDANCY...always
REDUNDANCY.

I like redundant charging, too. The Perkins has TWO alternators, 80A for
the starting battery on the original engine mount and 120A on the house
batteries connected to a diode separator that charges both banks. If one
alternator fails, simply put both switches in BOTH and either one of the
alternators charges all the batteries at once. Power is our FRIEND.


"There are other positive benefits of a single house bank versus two."
"...a gain in effective capacity results because the rate of discharge
relative to battery capacity is reduced."

Nope...doesn't wash.....

The ampere-hour rating of any battery, even his, depends on the LOAD
current on that battery. The lighter the load, the higher the actual amp-
hour capacity of the battery. Put a 1A light bulb across a 130AH deepcycle
and time how long it takes it to die.....MUCH longer than 130 hours. 130AH
is the 20 amp load rating. Draw 50A off it and it's dead in minutes, not
hours, because the chemical reaction of acid and lead can only happen so
fast.

When one has two battery banks, the load current is halved on them. The
real amp-hour rating at this load goes up significantly as the results.
Nigel has it backwards!


FYI
http://www.amplepower.com/wire/dual_alt/index.html

Dual Alternator Controller

REDUNDANCY....always REDUNDANCY. This controller fails you gots NO
CHARGING! Two SIMPLE regulators reduces your total failure probablility to
near zero.

I like integrated regulators....GASP!...WHAT?!!....Integrated regulators?!
How can this be?!

The integrated, internal regulators in all your cars works just fine. When
was the last time you lost a REGULATOR when your car's alternator went out?
You didn't. You lost a brush or a more probably a rectifier diode. The
internal regulator reduces the wiring maze in the engine room, another
point of failure. The internal regulator is made for THAT alternator, not
a whole series of alternators like these gee-whiz expensive beasts with
their LED lights, plugs that corrode, etc. What is this fascination with
ever-increasing the complexity of such a simple device? Regulators are
VERY accurately controlled by Zener diodes in 2005. They've been that way
for decades. You don't need to be screwing around with "settings" on
regulators. Put 14-14.5V to the house battery and he's one happy camper!

The other thing I don't like, but Lionheart has already, is these BIG
alternators. Ever look at a battery charger? Do you charge it at 120
amps? No? Why? Battery charging chemistry is S-L-O-W! Time is your
charging battery's friend. The longer you take to charge it, the more
charge it absorbs and the safer it is for it....especially DEEP CYCLE house
batteries. Starting batteries, like your car battery, made of lots more
plates with huge surface areas to create huge currents for seconds can
charge at much higher rates than a deep cycle with its low count, thick
plates with much lower surface area. The charging current per square inch
of plate surface is the same, it's just that the deep cycle has lots LESS
surface area on thicker plates. This charging them for an hour at 100A is
absurd! The chemistry just can't absorb the current you're shoving in
there fast enough, so it rids itself of excess by getting HOT. Heat
generated at high charging rates DOESN'T charge it. You end up with a gas
station surface charge, which doesn't last. Golf cart 230AH batteries LOVE
about 25-30A of charge. They hardly get warm and the specific gravity goes
all the way up to 1.260 without percolating them. So, why do we need an
alternator bigger than 30A + the house load current while we're charging?
We don't.


Ample power......two banks of L-16s at 1.260 gravity....ahh...ample power.

--
Larry

In article ,
(Mic) wrote:

Do you consider it better to have one or 2 sets of house batteries?

snip

http://www.amplepower.com/primer/prefer/index.html

" The Preferred System

The Preferred System consists of a single house bank, and a dedicated
starter battery for all engines. A separate generator battery is
sometimes present. "

We have two banks for much the same reasons as Rosalie, but for our
moderate needs that are now mostly handled by solar, I'm tending towards
a smallish battery directly connected to the alternator with a
paralleling switch if I need to charge the house.

That would make it impossible to fry the alternator by switching the
wrong way by accident. In addition, I could shorten the primary battery
cables considerably, making it more likely that we'll start under all
conditions. The only downside is if the starting battery dies, but since
it won't usually have any but starting loads, it'll last a longer; I've
had original-equipment car batteries last a dozen years.


--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/