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,

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.

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

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.

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.

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.

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.

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

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

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

Electrical, battery, question
 

snip

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.

I thought 12.2v was 50% charged (12v lead acid battery). No idea were I got
that idea from, but it would explain why I struggle to keep my batteries
above it. I have 4 x 12v 135amp batteries connected as two pairs of 12v
batteries wired in series then wired together in parallel, to give 24v.
Something I have often wonder about is if I should connect them to the
electrical system with both positive and negative coming off one pair, or
the positive off one pair and the negative off the other.

Electrical, battery, question
 

"krj" wrote in message
...
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.

Meltdown!

Well, he was talking in the context of solar panel re-charging.

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

Electrical, battery, question
 

the math is easy enough to figure out, a lot of people gave you some
good information on this thread. for my own deep cycle systems i've
noticed it never works out like the math says it should though, never,
not in actual practice. you kind of imagine all these perfect numbers,
12 volts and 100 amp hours and that means you can do this task for
such-and-such a time and it'll take your solar cell such-and-such time
to recharge and all this. and there are even charts that give you an
idea of the danger areas for depth of discharge, that is, discharging
the batteries too much and too often, and how many times you can go to
certain levels before you have to get new batteries, etc. my
experience has been that in the end the math is ok for like a really
general idea, but that's about it. the math quickly turns into
non-sense in the face of harsh reality. in actual practice your
battery bank is always in some weird state of charge that's hard to
measure because it varies so much with temperature, battery age, what
angle the batteries are sitting at, how much water you put in it last
time you serviced them, etc. and who knows what your solar panels are
doing depending on time of day, cloud cover, etc, and the same for your
wind generator, and even your alternator, none of it has very much to
do with what it's rated at, or what the specifications claim it's going
to do. then your loads are so variable too, which lights will you have
on at which times ? how often is the compressor going to flip on in
your refrigerator ? how many amps is your starter going to draw ?
does humidity affect any of it ? etc. in reality it's a crap shoot,
and nobody really has any idea what their system is doing most of the
time, and it's even hard to measure the voltage on the batteries
because power is going into them from the solar panels and things most
of the time, even on shady days. and even if you could measure the
battery banks voltage it doesn't give a real measure of the state of
charge. so you design it the best you can, fit in as many batteries as
you have space for, try to minimize how much power you are wasting, try
to keep everything maintained (especially your batteries), try to put
in as much power generation (solar and wind) as you can, then cross
your fingers and hope for the best. i mean, really, does anyone really
have any idea how many amp hours are in their battery bank right now ?
lol. yes, yes, i know, your battery power meter tells the whole truth
G. my personal experience has been that it's a bunch of voodoo. :)

Electrical, battery, question
 

In article dz7Df.1473$UY3.1361@trndny05,
"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.

Voltage is the pressure, amps is the volume per time-period. Amp-hours
(AH) = the total volume.

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. ?

I suspect they're small 12v, possibly 6, unlikely to be 8. Others
covered the series-parallel stuff.

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?

These last depend on your usage, though I almost guarantee that one
large battery will do better than a "bunch" of little ones.

We have simple needs, so are comfortable with a group 31 (120 AH) as our
primary, with another kept in reserve. Our 12w solar panel keeps up with
our needs most of the time and can bring the battery up enough to start
the engine by mid-morning. When we're away for a few days, the panel
brings the battery to full power, which is a couple of days' normal
usage.

When we next upgrade, I'm going to move the better 31 to right next to
the engine and "hardwire" it to the starter with short cables; No
switch, though it'll be fused of course. The house bank --probably two
6v-- will primarily be solar charged, though we will be able to parallel
it to the starting battery for a fast recharge or extra starting power.

--
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/