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posted to rec.boats.cruising
Thomas Wentworth
 
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Default Electrical, battery, question

I get so confused when it comes to electric power, especially battery
output. How many AMPs can a battery put out before the battery is dead?
Say, a 12 volt battery. Could you put this as .. "if you have on a light
for xxx hours the battery is gone".

I know AMPs are the flow of power and volts is the possible amount ..
measure of flow and time . and light bulb.

Why am I asking? I was looking at this boat on a web site and the owner had
added a bank of small batteries. About half the size of the marine ones I'm
use to. The batteries were tied together so they became on big battery in
power possibility.

Now,, if he had 6 batteries and each one is an 8 volt .. does this mean he
has 8x6 = 48 volts of possible power? And how does this work out to amps. ?

batteries are heavy. how many do you carry. wouldn't a bunch be bad for
the boat??

also.. solar power.. how much power does one of those things give you?

thanks,


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posted to rec.boats.cruising
Dennis Pogson
 
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Default Electrical, battery, question

Thomas Wentworth wrote:
I get so confused when it comes to electric power, especially battery
output. How many AMPs can a battery put out before the battery is
dead? Say, a 12 volt battery. Could you put this as .. "if you have
on a light for xxx hours the battery is gone".

I know AMPs are the flow of power and volts is the possible amount ..
measure of flow and time . and light bulb.

Why am I asking? I was looking at this boat on a web site and the
owner had added a bank of small batteries. About half the size of
the marine ones I'm use to. The batteries were tied together so they
became on big battery in power possibility.

Now,, if he had 6 batteries and each one is an 8 volt .. does this
mean he has 8x6 = 48 volts of possible power? And how does this work
out to amps. ?

batteries are heavy. how many do you carry. wouldn't a bunch be bad
for the boat??

also.. solar power.. how much power does one of those things give
you?

thanks,


The voltage has absolutely nothing to do with it. A 12-volt battery has a
stated capacity in amp/hours, and will last until exhausted when a 12-volt
load is applied. How big a load? You tell us!

If a battery's stated capacity is say, 100A/H, then a 5-amp bulb would in
theory burn for 100/5=20 hours, but in practice this is simply a guide,
since the bulb would go dim once the battery's voltage dropped below the
12-volts output, and in fact the bulb might still be showing some faint
light after 30 hours or more.

For the six batteries you mention to give 48 volts they would have to be
wired in series, i.e. each one positive to negative, whereas in parallel
(positive to positive and negative to negative) they would give you 12
volts, but the capacity would be the sum of the six batterys' capacities.

Space and layout permitting, It is better to have as big a battery as the
boat will permit for house use, and a starter battery appropriate to the
size of the engine installed, banks of batteries are fine until one packs
in, then you have to find the culprit and remove it from the bank. Auto
batteries are often used as the starter battery, whereas a slow discharge
battery is better for the house requirements. The 2 batteries can be wired
for charging purposes by a splitting diode or similar arrangement which
allows them both to be charged together, but discharged separately.

Amps = volume and volts = pressure, think of a hosepipe.


  #3   Report Post  
posted to rec.boats.cruising
Peter Bennett
 
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Default Electrical, battery, question

On Sun, 29 Jan 2006 19:34:10 GMT, "Dennis Pogson"
wrote:

Thomas Wentworth wrote:


Now,, if he had 6 batteries and each one is an 8 volt .. does this
mean he has 8x6 = 48 volts of possible power? And how does this work
out to amps. ?


For the six batteries you mention to give 48 volts they would have to be
wired in series, i.e. each one positive to negative, whereas in parallel
(positive to positive and negative to negative) they would give you 12
volts, but the capacity would be the sum of the six batterys' capacities.


The OP's suggested 8 volt batteries - if he connects them in parallel,
they'll still give him 8 volts.


--
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
  #4   Report Post  
posted to rec.boats.cruising
chuck
 
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Default Electrical, battery, question

Well, if the six batteries are wired in series to get 48 volts, the
capacity of the six is essentially the capacity of the smallest-capacity
battery of the lot. As the smallest-capacity battery discharges, its
internal resistance increases, which prevents the discharge through it
of the batteries with greater capacity. If the six are identical,
however, then the capacity in amp-hours of the six in series is the same
as the capacity of any one of them alone. Only the voltage changes.

Or is that more confusing?

Chuck



Peter Bennett wrote:
On Sun, 29 Jan 2006 19:34:10 GMT, "Dennis Pogson"
wrote:


Thomas Wentworth wrote:



Now,, if he had 6 batteries and each one is an 8 volt .. does this
mean he has 8x6 = 48 volts of possible power? And how does this work
out to amps. ?



For the six batteries you mention to give 48 volts they would have to be
wired in series, i.e. each one positive to negative, whereas in parallel
(positive to positive and negative to negative) they would give you 12
volts, but the capacity would be the sum of the six batterys' capacities.



The OP's suggested 8 volt batteries - if he connects them in parallel,
they'll still give him 8 volts.


  #5   Report Post  
posted to rec.boats.cruising
Wayne.B
 
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Default Electrical, battery, question

On Mon, 30 Jan 2006 00:56:53 GMT, chuck wrote:

Well, if the six batteries are wired in series to get 48 volts,


8 volt batteries are not that common except on boats with 32 volt
electrical system like the older Hatteras motor yachts.

Much more common on sailboats are banks of 6 volt batteries wired in
series-parallel to yield high capacity 12 volt battery banks.

Four 6 volt golf cart batteries in series parallel will give you about
440 amp-hours of capacity but in actual practice it is a bad idea to
discharge below the 50% level since that will greatly shorten batter
life. You can get a rough idea of discharge level by looking at a
digital voltmeter when the batteries are under load. 12.6 volts is
fully charged, 11.6 volts is about 50%, and 10.5 is fully discharged.



  #6   Report Post  
posted to rec.boats.cruising
chuck
 
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Default Electrical, battery, question

Yeah. Should've mentioned that. I was trying to respond to the original
question as posed. He seemed to be asking about the capacity of
series-connected batteries.

Chuck

Wayne.B wrote:
On Mon, 30 Jan 2006 00:56:53 GMT, chuck wrote:


Well, if the six batteries are wired in series to get 48 volts,



8 volt batteries are not that common except on boats with 32 volt
electrical system like the older Hatteras motor yachts.

  #7   Report Post  
posted to rec.boats.cruising
Dennis Pogson
 
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Default Electrical, battery, question

chuck wrote:
Yeah. Should've mentioned that. I was trying to respond to the
original question as posed. He seemed to be asking about the capacity
of series-connected batteries.

Chuck

He would be better reading a copy of "The 12-volt Doctor's Practical
Handbook", a must for all who find boat electrical technology difficult.
Sadly, any .pdf copies seem to have disappeared from the Web, and you have
to pay around $30 for a hard copy.


Dennis.


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posted to rec.boats.cruising
News f2s
 
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Default Electrical, battery, question


"Thomas Wentworth" wrote in message
news:dz7Df.1473$UY3.1361@trndny05...
I get so confused when it comes to electric power, especially
battery output. How many AMPs can a battery put out before the
battery is dead? Say, a 12 volt battery. Could you put this as
.. "if you have on a light for xxx hours the battery is gone".

I know AMPs are the flow of power and volts is the possible
amount .. measure of flow and time . and light bulb.

Why am I asking? I was looking at this boat on a web site and
the owner had added a bank of small batteries. About half the
size of the marine ones I'm use to. The batteries were tied
together so they became on big battery in power possibility.

Now,, if he had 6 batteries and each one is an 8 volt .. does
this mean he has 8x6 = 48 volts of possible power? And how does
this work out to amps. ?


1. Volts = pressure. Add batteries nose to tail (+ to -, or in
series) and you add up their voltage. The most common sipboard
voltage for yachts 20ft to 40ft is 12v (actually, 10.5v to 12.7v,
depending on their charge state).

2. Battery capacity is shown in ampere x hours (AH). Very
approximately, divide the AH by the number of amps you're using,
and that's how many hours you'll get out of the battery if it's
fully charged.

3. If you join similar voltage batteries nose to nose, and tail
to tail (in parallel), the voltage will stay the same, but the
capacity will multiply by the number of batteries.

4. If you re-charge your discharged 12v battery using a 48watt
(power: watts = volts x amps) solar panel, you should get 4 amps
out of it (48/12), and if it keeps up its 4a (which it won't)
you'll get 4 x (the number of hours) of AH back into the battery.

Those are the basic rules. They get screwed up by efficiency (or
lack of it), but they're a good start.

Have fun doing the sums.

JimB
http://www.jimbaerselman.f2s.com/sw_peloponese.htm



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posted to rec.boats.cruising
krj
 
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Default Electrical, battery, question

News f2s wrote:
"Thomas Wentworth" wrote in message
news:dz7Df.1473$UY3.1361@trndny05...

I get so confused when it comes to electric power, especially
battery output. How many AMPs can a battery put out before the
battery is dead? Say, a 12 volt battery. Could you put this as
.. "if you have on a light for xxx hours the battery is gone".

I know AMPs are the flow of power and volts is the possible
amount .. measure of flow and time . and light bulb.

Why am I asking? I was looking at this boat on a web site and
the owner had added a bank of small batteries. About half the
size of the marine ones I'm use to. The batteries were tied
together so they became on big battery in power possibility.

Now,, if he had 6 batteries and each one is an 8 volt .. does
this mean he has 8x6 = 48 volts of possible power? And how does
this work out to amps. ?



1. Volts = pressure. Add batteries nose to tail (+ to -, or in
series) and you add up their voltage. The most common sipboard
voltage for yachts 20ft to 40ft is 12v (actually, 10.5v to 12.7v,
depending on their charge state).

2. Battery capacity is shown in ampere x hours (AH). Very
approximately, divide the AH by the number of amps you're using,
and that's how many hours you'll get out of the battery if it's
fully charged.

3. If you join similar voltage batteries nose to nose, and tail
to tail (in parallel), the voltage will stay the same, but the
capacity will multiply by the number of batteries.

4. If you re-charge your discharged 12v battery using a 48watt
(power: watts = volts x amps) solar panel, you should get 4 amps
out of it (48/12), and if it keeps up its 4a (which it won't)
you'll get 4 x (the number of hours) of AH back into the battery.


A 100 amp hour battery. 100/5amps = 20 hours. Yes. 100/50 = 2 hours.
NO! Maybe 20 minutes.

Those are the basic rules. They get screwed up by efficiency (or
lack of it), but they're a good start.

Have fun doing the sums.

JimB
http://www.jimbaerselman.f2s.com/sw_peloponese.htm



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posted to rec.boats.cruising
Evan Gatehouse
 
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Default Electrical, battery, question

Peter Bennett wrote:
On Sun, 29 Jan 2006 19:34:10 GMT, "Dennis Pogson"
wrote:


Thomas Wentworth wrote:



Now,, if he had 6 batteries and each one is an 8 volt .. does this
mean he has 8x6 = 48 volts of possible power? And how does this work
out to amps. ?



For the six batteries you mention to give 48 volts they would have to be
wired in series, i.e. each one positive to negative, whereas in parallel
(positive to positive and negative to negative) they would give you 12
volts, but the capacity would be the sum of the six batterys' capacities.



The OP's suggested 8 volt batteries - if he connects them in parallel,
they'll still give him 8 volts.


Perhaps 3 x 8V = 24V?

Evan Gatehouse
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