Electric motors and battery combinations...>>>

I'm looking for information about electric motors and the most efficient
battery combinations in terms of weight of adding a battery vs. the power
that going to 24volt might give me. I live in an area that doesn't allow
gas motors on its reservoirs; only electric motors, so I could only power my
12' jon boat with electric. I'd like to match up the most efficient
combination of motor size, battery, and weight. I would like to know if I
get longer run time and/or more power with a 50lb 12volt motor or a similar
sized 24volt motor? Or, would I get a better weight-power-endurance
combination getting a 36volt, 100+ lb motor??

Also, would I get more run time from 2 batteries (1 to run, and one as a
spare, i.e., "refuel") with a 12volt motor, or 2 batteries running
simultaneously on a 24volt motor?

questions, questions, questions...

--
Marty S.
Baltimore, MD USA

"Marty S." wrote in message ...
I'm looking for information about electric motors and the most efficient
battery combinations in terms of weight of adding a battery vs. the power
that going to 24volt might give me. I live in an area that doesn't allow
gas motors on its reservoirs; only electric motors, so I could only power my
12' jon boat with electric. I'd like to match up the most efficient
combination of motor size, battery, and weight. I would like to know if I
get longer run time and/or more power with a 50lb 12volt motor or a similar
sized 24volt motor? Or, would I get a better weight-power-endurance
combination getting a 36volt, 100+ lb motor??

Also, would I get more run time from 2 batteries (1 to run, and one as a
spare, i.e., "refuel") with a 12volt motor, or 2 batteries running
simultaneously on a 24volt motor?

questions, questions, questions...

I might be wrong, and this is strictly my experience speaking but I used to run a 12 volt system
long ago in a galaxy far, far away. I had a 42 pound thrust motor and I would drain the battery
dead long before I was ready to come in for the day. Then I went to two, 12 volt batteries on the
same motor and found that I could go all day without problems.

Then, I sold that boat and got one with a 24 volt system and a 60 pound thrust motor. I couldn't
believe how long I could go on a single charge! It was far longer than running the 12 volt system
with two batteries. I think that 36 volt would be overkill, but I think that if you were to get a
24 volt, 65 pound thrust system, you would be VERY pleased with the results. I believe that if you
are running a larger than needed motor, you can run it on lower settings, thus saving on batteries.
You'll have to run a lesser thrust motor on higher settings to get the same performance, and use up
the batteries faster in the process.
--
Steve
OutdoorFrontiers
http://www.outdoorfrontiers.com
G & S Guide Service and Custom Rods
http://www.herefishyfishy.com

Perhaps I'm missing something... but wouldn't a 36 volt system require 3
deep cycle battteries... in a 12' boat? That's about 150lbs just in
batteries. I run a 36lbs motor on 1 deep cycle battery. I can run it all day
long... probably 2 days without recharging. But deep cycle batteries are
ment to be recharged after each use. So I question why you would want more
then a few days use from your battery/motor combination.

"Marty S." wrote in message
...
I'm looking for information about electric motors and the most efficient
battery combinations in terms of weight of adding a battery vs. the power
that going to 24volt might give me. I live in an area that doesn't allow
gas motors on its reservoirs; only electric motors, so I could only power
my
12' jon boat with electric. I'd like to match up the most efficient
combination of motor size, battery, and weight. I would like to know if I
get longer run time and/or more power with a 50lb 12volt motor or a
similar
sized 24volt motor? Or, would I get a better weight-power-endurance
combination getting a 36volt, 100+ lb motor??

Also, would I get more run time from 2 batteries (1 to run, and one as a
spare, i.e., "refuel") with a 12volt motor, or 2 batteries running
simultaneously on a 24volt motor?

questions, questions, questions...

On the other hand, I have a 50 pound thrust Minnkota on my little 14-1/2
foot glass boat. I'm hard on the battery, but I can easily fish two long
days without a charge. I do run a group 29 deep cycle battery.



RichZ©
www.richz.com/fishing

On Thu, 18 Dec 2003 21:53:30 -0500, "Marty S."
wrote:
I'm looking for information about electric motors and the most efficient
battery combinations in terms of weight of adding a battery vs. the power
that going to 24volt might give me. I live in an area that doesn't allow
gas motors on its reservoirs; only electric motors, so I could only power my
12' jon boat with electric. I'd like to match up the most efficient
combination of motor size, battery, and weight. I would like to know if I
get longer run time and/or more power with a 50lb 12volt motor or a similar
sized 24volt motor? Or, would I get a better weight-power-endurance
combination getting a 36volt, 100+ lb motor??

Also, would I get more run time from 2 batteries (1 to run, and one as a
spare, i.e., "refuel") with a 12volt motor, or 2 batteries running
simultaneously on a 24volt motor?
==================================================

All other things being equal, a 24 volt system should be more
efficient. The reason is less voltage drop in the cables (assuming
equal size). When it comes to batteries, there is no substitute for
weight. More lead equals more power. Regarding the question of
running from two batteries at the same time, or from one then the
other, I'd vote for both batteries at once. You should get longer
battery life that way since you'd be less likely to discharge below
the 50% level. The advantage of course to first one battery, then the
other, is the ability to get home after you draw down the first.
Drawing down the batteries to zero is a recipe for short life however.

You can use two group 27 batteries wired in parallel. It will pull the boat
around all day long. By putting them in parallel, it doubles the run time.
The AC Delcos are 160 minute reserve capacity batteries. By putting them in
parallel, it gives me 320 minutes of 25amp capacity.
You need to get deep cell batteries with the highest amp available. Check
amp draw on different model motors and get one with a low amp draw at full
power.

What is Amp Draw?

.. Amp draw is the measurement of electrical current drawn from a storage
battery (or battery), while the trolling motor is being operated at maximum
speed.
.. Minn Kota 's published amp draw figures represent actual on the water
conditions (with all of the motor 's wiring, switches and circuitry in the
electrical system as the test measurement is taken).
.. Approximate length of running time when operation a trolling motor at full
power can be determined with a motor 's amp draw and the battery amp hour
rating.
Example: A single 120 amp hour, 12 volt battery and a 12 volt trolling motor
drawing 20 amps at the highest speed setting will run for about 3.4 hours.
.. The formula for the calculation is as follows:
..85 A.H.R. = Hours of running time. (A.H.R.= Battery Amp Hour Rating)
M.A.D. (M.A.D. = Motor Amp Draw)

.. As the speed setting is reduced the motor amp draw is also reduced.
.. A motor drawing 30 amps at high speed may only draw 5 amps at the slowest
speed. The same motor that will theoretically run about 3.4 hours at high
speed will run for over 20 hours at the slowest speed.

Sarge

"Marty S." wrote in message
...
I'm looking for information about electric motors and the most efficient
battery combinations in terms of weight of adding a battery vs. the power
that going to 24volt might give me. I live in an area that doesn't allow
gas motors on its reservoirs; only electric motors, so I could only power
my
12' jon boat with electric. I'd like to match up the most efficient
combination of motor size, battery, and weight. I would like to know if I
get longer run time and/or more power with a 50lb 12volt motor or a
similar
sized 24volt motor? Or, would I get a better weight-power-endurance
combination getting a 36volt, 100+ lb motor??

Also, would I get more run time from 2 batteries (1 to run, and one as a
spare, i.e., "refuel") with a 12volt motor, or 2 batteries running
simultaneously on a 24volt motor?

questions, questions, questions...

--
Marty S.
Baltimore, MD USA

The responses you're getting are on target and informative. I would suggest
you look for a website for electric only "jon boat" tournaments. You may
very well find some detailed info or a person willing to show what their
group does. Some of those guys put a lot of thought into their systems and
many are just amazing.
--
Shelby Foles,

"Marty S." wrote
I'm looking for information about electric motors and the most
efficient battery combinations in terms of weight of adding a
battery vs. the power that going to 24volt might give me.

I don't know anything about electric boats, but I know a thing or two about
electricity. The amount of useful work, ie boat moving, that you can get out
of a motor and battery combination is a function of voltage and current. If
you use more voltage, you need less current to do the same work. Conversely
you need more current to do the same work with lower voltage. A battery has
a limited amount of current in it that you can pump out into your motor to
do work. If you put multiple batteries in parallel, the voltage remains the
same but you have a greater quantity of current available to you. If you put
multiple batteries in series, you increase the voltage, but the current
capacity is the same as a single battery. Theoretically, it's a wash,
assuming that you're using adequate wiring so that you're not losing a lot
of power heating the wires. I suspect that the real differences we see in
run time depend primariliy on the efficiency of the propulsion unit, that is
how much of the energy that the battery squirts into the motor gets
converted to moving the boat and how much of it gets thrown overboard as
waste. I'm guessing that, all else being equal, typical 24 volt boat motors
probably have an efficiency edge over 12 volt ones because their internal
components are moving less current around and it's easier and less expensive
to manufacture an efficient low current device than an efficient high
current one. If you're using something to control the speed of the motor,
the speed controller's efficiency would also come into play and the same
rules apply.

"Marty S." wrote in message
...


I would like to know if I
get longer run time and/or more power with a 50lb 12volt motor or a
similar
sized 24volt motor? Or, would I get a better weight-power-endurance
combination getting a 36volt, 100+ lb motor??

The full answer is not so simple. A partial answer that makes a bunch of
assumptions that will be correct in most cases would be that the higher
voltage system will be a lot more efficient.

If you look just at the motor, the ability to turn electrical power into
torque is a function of the number of amps flowing through the wire and the
number of turns that the wire makes around the motor pole. If you have the
luxury of allowing a large physical size on the motor then you can trade off
number of turns for amps and use just about any voltage you want. When you
want the motor to be compact, it is usually easier to have a low voltage,
low turns, high amperage design.

If the motor was the only consideration in the equation that would be the
end of the disscussion. Unfortunately, you also need to consider the wiring
to the motor, the controls and the batteries that feed the motor. All of
these items favor lower current, higher voltage designs. While the physics
of the motor can trade off voltage for current, the losses incurred in the
wiring and controls will be effected only by the current, and will have no
"trade off". If you double the current, then you need to double the wire
size or you will lose twice as much energy into heating the wire.

The biggest single impact on efficiency will be the rate at which current is
drawn from the battery. Deep cycle batteries are typically rated at a "20
hour" rate or lower. At a higher draw, the battery will supply less. A
typical battery, say a "Trojan" 27 series, is rater at 105 amp-hours at the
20 hour rate (5.25 amps for 20 hours). If you increase the current demand up
to the 5 hour rate you will only get 79 amp-hours (this information is from
the Trojan Battery web site). In general, the higher the current, the less
efficient the battery will be.

For maximum run time you will want the lowest current draw, hence the higher
voltage system.




Also, would I get more run time from 2 batteries (1 to run, and one as a
spare, i.e., "refuel") with a 12volt motor, or 2 batteries running
simultaneously on a 24volt motor?

Again, maximum run time will occur when the current that the battery sees is
at a minimum. You will get a lot more run time if you run two batteries in
parallel than if you ran one until it was dead and then switched to the
other.


Rod McInnis

"Marty S." wrote in message
...
I'm looking for information about electric motors and the most efficient
battery combinations in terms of weight of adding a battery vs. the power
that going to 24volt might give me. I live in an area that doesn't allow
gas motors on its reservoirs; only electric motors, so I could only power
my
12' jon boat with electric. I'd like to match up the most efficient
combination of motor size, battery, and weight. I would like to know if I
get longer run time and/or more power with a 50lb 12volt motor or a
similar
sized 24volt motor? Or, would I get a better weight-power-endurance
combination getting a 36volt, 100+ lb motor??

Also, would I get more run time from 2 batteries (1 to run, and one as a
spare, i.e., "refuel") with a 12volt motor, or 2 batteries running
simultaneously on a 24volt motor?

questions, questions, questions...

--
Marty S.
Baltimore, MD USA



One of the local guides I know uses a 36 volt system, Running full power
against the current all day he has battery to spare for another day if he
can't get it recharged. On top of that, guess what.. He only has three
batteries in his boat. Yup the battery for the big motor is wired in series
with the other two for his 36 volts.


--
Bob La Londe
Yuma, Az
http://www.YumaBassMan.com
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