Electric motors and battery combinations...>>>

"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'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
Promote Your Fishing, Boating, or Guide Site for Free
Simply add it to our index page.
No reciprocal link required. (Requested, but not required)

If you know, I would like his assessment of risk using his "big motor"
battery for trolling. That is, does he accept his risk that he will be
caught without starting power, does he monitor his voltage or battery
condition on a regular basis for reserve starting power or any other method?
It sounds like a good idea. I am due to replace my 24V TM in the near
future and would like some thoughts on the 36V system with 3 batteries
maximum in the boat. What would be involved with the standard charging
system, 12V, that is in use on the "big motor" now.
Al Crumrine

"Bob La Londe" wrote in message
...
Snipped
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.

Electrically the battery on the big motor will charge normally when the big
motor is on.

As to risk. He told me has has been doing it that way for about four years
now with no problems.



"Acee" wrote in message
news:HvOEb.403945$Dw6.1257180@attbi_s02...
If you know, I would like his assessment of risk using his "big motor"
battery for trolling. That is, does he accept his risk that he will be
caught without starting power, does he monitor his voltage or battery
condition on a regular basis for reserve starting power or any other
method?
It sounds like a good idea. I am due to replace my 24V TM in the near
future and would like some thoughts on the 36V system with 3 batteries
maximum in the boat. What would be involved with the standard charging
system, 12V, that is in use on the "big motor" now.
Al Crumrine

"Bob La Londe" wrote in message
...
Snipped
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.

Sounds promising. Thanks.
Al Crumrine

"Bob La Londe" wrote in message
...
Electrically the battery on the big motor will charge normally when the
big
motor is on.
As to risk. He told me has has been doing it that way for about four
years
now with no problems.

"Acee" wrote in message
news:HvOEb.403945$Dw6.1257180@attbi_s02...
If you know, I would like his assessment of risk using his "big motor"
battery for trolling. That is, does he accept his risk that he will be
caught without starting power, does he monitor his voltage or battery
condition on a regular basis for reserve starting power or any other
method?
snipped

That is the only way I have ever seen anyone run a 36V.

"Bob La Londe" wrote in message
...
"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
Promote Your Fishing, Boating, or Guide Site for Free
Simply add it to our index page.
No reciprocal link required. (Requested, but not required)

Really? I have seen lots of guys run four batteries aorund here.

Three plus one.




"Steve Erwin" wrote in message
...
That is the only way I have ever seen anyone run a 36V.

"Bob La Londe" wrote in message
...
"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
Promote Your Fishing, Boating, or Guide Site for Free
Simply add it to our index page.
No reciprocal link required. (Requested, but not required)

"Steve Erwin" wrote in message ...
That is the only way I have ever seen anyone run a 36V.

My Cobra Coosa 216 came with a 36 volt system. It has 3 deep cycle batteries and a starting
battery.
--
Steve
OutdoorFrontiers
http://www.outdoorfrontiers.com
G & S Guide Service and Custom Rods
http://www.herefishyfishy.com

"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

Perhaps you could use a "Honda" EX1000 generator to recharge the
batteries on the fly. The unit is lightweight, whisper quiet and puts
out 7 amps ac and 8 amps dc. Add in a decent battery charger and it
would be like having an alternator. I keep larger (EX2000) unit on my
boat (26' Formula PC) just to maintain the house batteries when
anchored. The gene sips fuel with an eyedropper, and I can carry on a
normal conversation with the wife standing next to it.

Just a thought,

CF

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?

questions, questions, questions...

--
Marty S.
Baltimore, MD USA