(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 ...

We do have a large number of batteries - each bank is eight 6 volt
batteries. I think it would be hard to find enough space for that
many batteries in one place without putting them into the living
space.


My gosh!

That is a bunch of batteries.

it would be helpful to know what you are useing them all for.

For what i used on my ancient ChisCraft 28 ft'r. was a normal 800CCA
battery for the one engine, and an 8-D "Cat" battery for the cabin. i
used a battery isolator which splits the two systems. so your cabin
battery never runs down your start battery. but when engine is running
both sets are charged. pretty simple and effective.

however it's probably obvious that my demands are far different from
yours.


Tim

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

"Rosalie B." wrote in message
...
"Doug Dotson" dougdotson@NOSPAMcablespeedNOSPAMcom wrote:
"Rosalie B." wrote in message
. ..
"Doug Dotson" dougdotson@NOSPAMcablespeedNOSPAMcom wrote:

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

We have two house banks, and no starting battery. I think there are
advantages each way.

Not really.

Well you have said what you prefer,

What else would I have contributed.

and I have said what Bob prefers.

What do you prefer?

Are you saying that Bob has no logical reason for using two house
banks?

Yes.

If so, that is very annoying and rude of you. If not, then
you need to work on being more tactful.

No I don't You need to get into the 21st century..

With two house banks, we can be sure that we won't use up all the
battery capacity overnight, and will have plenty of power to start the
engine up in the morning.

Same with 1 hourse and one starting battery.

Not really.

Since most of our battery use is NOT for
starting the engine, it doesn't make any sense to have the type of
battery which is basically only good for that type of use.

Yes it is since a house bank is deep cycle which is different than a
starting battery.
Using a deep cycle battery to start an engine is hard on the battery and
if
for
some reason the engine is being hard to start, it may not provide enough
current
and will further damagage the bank.

It is
unused most of the time, and is basically wasted power.

Not wasted. Is your EPIRB wasted money? It is guaranteed to be
there when it is needed no matter how forgetful the operator is. The
battery
is small and cheap. Mine is 1300 CCA and cost about $70.

This is irrelevant. You might just as well say that the battery
operated searchlight is wasted money because we might never need it.
Or indeed any battery operated item. Doesn't have a thing to do with
starting batteries or house batteries.

And won't the
charging system have to be different for just the one battery, than
for the house bank?

Different, but not complex. A parallelling solenoid is the simplest
solution
and
something like The Eliminator or Echo Charge is the optimal solution.


We do have a large number of batteries - each bank is eight 6 volt
batteries. I think it would be hard to find enough space for that
many batteries in one place without putting them into the living
space.

Lost you here. Another point is one large unified house bank will have a
longer
total lifetime that two separate banks. I have a set of 2 8D gels that are
over
12 years old and still doing fine in almost everyday use. The boat has two
8D
AGM that have onlt barely started to loose capacity and are 6 years old.

We have had 8D wet cell batteries which came with the boat in 1998 as
the original house bank, and we replaced them with golf cart batteries
last year. When we bought her, the boat didn't have a second bank
or a starting battery IIRC.

Bob considered the cost and life span of the various types of
batteries, and decided that the life span of the new techie batteries
was not long enough to make up for the extra expense and trickier
charging problems. He figured he could replace the pack of wet cell
or golf cart 3 or 4 times for the cost of one battery pack of the more
'advanced' batteries, which would at best last twice as long. He
doesn't mind watering the batteries and checking on them occasionally.

Bob is wrong. The "techie" batteries are only about double the cost of
wet batteries and last more than twice the lifetime. Nothing "tricky" about
the charging, just set the charger to the right settings.

Bob converted a car to run on electricity and ran it to work for 5
years - in the car he had 16 or 18 six volt batteries plus a 12 volt
battery for the lights and radio.

That's only because the lights and radio needed 12V and the driver motors
run at a higher voltage. Different situation.

Yes I know. But he researched the batteries for the car, and he used
golf cart batteries for that too. The whole car conversion cost less
than $5,000.00, including buying the car to convert.

Golfcart batteries are very good. Higher energy density for the cost. But
none
of this has much to do with 1 house bank vs 2.

Doug
s/v Callista


"Mic" wrote in message
...
Do you consider it better to have one or 2 sets of house batteries?

From the material I have read and some practical experience one seems
to be a better answer with a separate battery for the starter or as
the dock side house battery.

I think Nigel Calder goes with the one set of batteries for the house?

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. "

"......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."

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

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

"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."


grandma Rosalie

"Tim" wrote in message
oups.com...
We do have a large number of batteries - each bank is eight 6 volt
batteries. I think it would be hard to find enough space for that
many batteries in one place without putting them into the living
space.


My gosh!

That is a bunch of batteries.

it would be helpful to know what you are useing them all for.

For what i used on my ancient ChisCraft 28 ft'r. was a normal 800CCA
battery for the one engine, and an 8-D "Cat" battery for the cabin. i
used a battery isolator which splits the two systems. so your cabin
battery never runs down your start battery. but when engine is running
both sets are charged. pretty simple and effective.

however it's probably obvious that my demands are far different from
yours.

I think we are talking about cruising sailboats here.


Tim

"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

"Tim" wrote:

We do have a large number of batteries - each bank is eight 6 volt
batteries. I think it would be hard to find enough space for that
many batteries in one place without putting them into the living
space.

My gosh!

That is a bunch of batteries.

it would be helpful to know what you are useing them all for.

We have a CSY 44. The refrigeration is either engine driven or shore
power, and is not on the 12V system. We have 4 solar panels and a
wind generator to charge the batteries, although if we are on the hook
or a mooring, we run the engine twice a day for 35-40 minutes for the
refrigeration.

Otherwise, everything is on the 12v system.

We really don't have a lot of things that other people have that
require power. We don't have a power windlass. We don't have A/C.
We don't have a microwave. We have a propane stove, and no heater,
except that if it gets cold (below 45 deg F) we will go into a marina
and plug into shore power to run a little electric space heater.

We do have 2 Lectrasan toilets, a DirecTV dish with a Follow Me
antenna, and two TVs and two DirecTV receivers. We have a LCD radar,
an autopilot, and I run the computers most of the time. We have 12V
reading lights. Bob has a whole bunch of tools, and some of them are
12V power tools and some he runs off an inverter (like the sewing
machine).

I sometimes plug the phones in to charge them. We have a SSB and two
VHF radios (one of which is on most of the time we are on the boat),
plus a couple of AM/FM radio/CD players and one or two little fans.
We have a pressure water system. And of course running lights etc.

For what i used on my ancient ChisCraft 28 ft'r. was a normal 800CCA
battery for the one engine, and an 8-D "Cat" battery for the cabin. i
used a battery isolator which splits the two systems. so your cabin
battery never runs down your start battery. but when engine is running
both sets are charged. pretty simple and effective.

however it's probably obvious that my demands are far different from
yours.


Tim

grandma Rosalie

Jeff wrote in :

Reaching the cabin or bilge would require going
through a major bulkhead.

If it's not GAS TIGHT where all the holes in its bulkheads go through with
the wires, it'll get in the cabin. Seal up all the cables to prevent it.
Proper stuffing tubes would be nice, instead of a little dab of RTV.

--
Larry

Peter Bennett wrote in
news.com:

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


It wasn't a shorted cell. It was a "dead cell". That cell had converted
lead and acid into lead sulphate crystals, so had a low gravity situation,
causing the ongoing charging problem because its voltage wouldn't come up.
These cells have quite low resistance, that's true. Lead sulphate is a
good conductor dissolved in water. What's missing is the acid. The other
cells simply forced current through the bad cell, attempting to charge it
backwards in the process, as you used it. It won't explode.

A normal battery cell that develops a short, where the plates actually
touch, is different from a dead cell. A thousand amps boils the
electrolyte as the acid-lead chemical reaction goes crazy. Acid steam
results and blows the cell, and the case, apart. Other cells may become
shorted from the impending distortion of the shorted cell pressing them
from the middle of the battery case. It isn't pretty....but it's quick!

--
Larry