The other day I saw what I took for a generator system that looked
like a trolling motor. I see that Ampair makes a couple of boat towed
water turbine units but they don't look like the unit I saw. I'm
curious as to what my trolling motor would generate if towed and
whether it could be used in a charge-pump circuit to do battery charge
duty. Anyone have any experience with towed generators?

We have a tow generator on our boat. When we went from VA to Portugal,
It generated 6-7 Amp per hour/ About 167 amp/day. It was a Ferris tow
generator.


Hanz


DaveC wrote:
The other day I saw what I took for a generator system that looked
like a trolling motor. I see that Ampair makes a couple of boat towed
water turbine units but they don't look like the unit I saw. I'm
curious as to what my trolling motor would generate if towed and
whether it could be used in a charge-pump circuit to do battery charge
duty. Anyone have any experience with towed generators?

Amps per day is not an interesting unit.

It doesn't include any indication of the voltage.
It doesn't include any indication of how long the power
was provided.
It's a rate of change, not "how much".

Watts is more interesting.

"Hanz" wrote in message ...
We have a tow generator on our boat. When we went from VA to Portugal, It generated 6-7 Amp per hour/ About 167 amp/day. It was a
Ferris tow generator.


Hanz


DaveC wrote:
The other day I saw what I took for a generator system that looked
like a trolling motor. I see that Ampair makes a couple of boat towed
water turbine units but they don't look like the unit I saw. I'm
curious as to what my trolling motor would generate if towed and
whether it could be used in a charge-pump circuit to do battery charge
duty. Anyone have any experience with towed generators?

Since the boat is moving 24 hours per day, then .....

Amps per day IS AN INTERESTING UNIT. HOW MUCH power does you boat using
in a 24 per period????

Hanz


Chuck Tribolet wrote:
Amps per day is not an interesting unit.

It doesn't include any indication of the voltage.
It doesn't include any indication of how long the power
was provided.
It's a rate of change, not "how much".

Watts is more interesting.

"Hanz" wrote in message ...

We have a tow generator on our boat. When we went from VA to Portugal, It generated 6-7 Amp per hour/ About 167 amp/day. It was a
Ferris tow generator.


Hanz


DaveC wrote:

The other day I saw what I took for a generator system that looked
like a trolling motor. I see that Ampair makes a couple of boat towed
water turbine units but they don't look like the unit I saw. I'm
curious as to what my trolling motor would generate if towed and
whether it could be used in a charge-pump circuit to do battery charge
duty. Anyone have any experience with towed generators?

Amps per day is a nonsense and meanigless unit and indicates a
complete misunderstanding of the principles involved.

Amps may be helpful when looking at an instantaneous situation. A
constant 5 amps into 13.8 volts would be enought to run the nav
instruments , radio and some of the load required for a fridge or
autopilot. A seemingly 'free' source of energy but to get the 69 watts
( 5 * 13.8 ) the system ie propellor, gearing , alternator, charger is
unlikely to be anything more than 20% efficient so around 350 watts
are exerted as drag on the boat, about 3/4hp. A worthwhile sacrifice I
would say.

To make sense you need to convert to amp/hours or watt hours.

"nimbusgb" wrote in message
oups.com...
Amps per day is a nonsense and meanigless unit and indicates a
complete misunderstanding of the principles involved.

Indeed.

To make sense you need to convert to amp/hours or watt hours.

Now you're making the same mistake: amps per day or amp/hours.... It is amps
* hours.

Meindert

A technical subject requires technically correct language. One amp for
one hour is one amp-hour. 167 amp days is a convertible unit, but not
a conventional one. To correctly express amp-hours implies watt-hours,
but amp days implies a basic misunderstanding or mis-expression of a
conventional arithmetic term, since techs use amp-hours. 167 amps at
nominal 12 volts for a day is 48,096 watt-hours, a big wack of power,
unrealistic given the circumstances. 6 amps all day is 24 hours times
6 amps is 144 amp-hours. At 12 volts, that's 1728 watt-hours, or about
as much as a fully employed electric kettle needs, all hour, every
hour.

So, you could charge the battery all day, if it's big enough, and then
boil kettles full of water to boiling and discard the boiled water,
not counting invertor losses, for about half an hour, maybe 6 kettles
full. Overall, you only get back about half of what you put into a
battery.

Terry K

Terry K wrote:
A technical subject requires technically correct language. One amp for
one hour is one amp-hour. 167 amp days is a convertible unit, but not
a conventional one. To correctly express amp-hours implies watt-hours,
but amp days implies a basic misunderstanding or mis-expression of a
conventional arithmetic term, since techs use amp-hours. 167 amps at
nominal 12 volts for a day is 48,096 watt-hours, a big wack of power,
unrealistic given the circumstances. 6 amps all day is 24 hours times
6 amps is 144 amp-hours. At 12 volts, that's 1728 watt-hours, or about
as much as a fully employed electric kettle needs, all hour, every
hour.

So, you could charge the battery all day, if it's big enough, and then
boil kettles full of water to boiling and discard the boiled water,
not counting invertor losses, for about half an hour, maybe 6 kettles
full. Overall, you only get back about half of what you put into a
battery.
Most of the power doesn't go into the batteries. It used to run the
freezer/frig, auto pilot and nav equipment. The left over power goes
into the batteries.


I can measure output of tow generator and also input/output of the
batteries.

The tow generator output 6 amp each hour for 28 days (from usa to europe).

We loss about 1/4 knots.

Hanz




Terry K

nimbusgb wrote in news:1181027399.917094.159070
@m36g2000hse.googlegroups.com:

Amps may be helpful when looking at an instantaneous situation. A
constant 5 amps into 13.8 volts would be enought to run the nav
instruments , radio and some of the load required for a fridge or
autopilot.

"Lionheart", an Amel Sharki 41 ketch, has a "shaft alternator" on her
freewheeling shaft. You must have a hydraulic transmission designed to
be free wheeled to use one, not just "leave it in neutral". The Perkins
transmission on the 4-108 is larger than most of them.

Her shaft turns, at 6 knots through the water, about 70-80 RPM. This
turns a big pulley made for a flat cogged belt. The pulley is about 12"
in diameter up near the back of the transmission. The belt drives a
special, slow-turning alternator, who, I'm guessing, is turning about 300
RPM at this speed. It's driving a 2KW Raymarine radar/color chart
plotter, Garmin 185 GPS/sonar, a string of B&G Network instruments,
including B&G Network Pilot electro-hydraulic autopilot, a Yeoman chart
table, a Dell Latitude w/HP Printer, a 12V fridge, bilge pump, water
pump, all the lights. Loaded down, the shaft speed drops, of course, but
she'll put out 15-18A at 14.2-14.4V to charge the 660AH golf cart beasts,
too.

As the Amel is already slower than dirt, a sturdy but leisurely cruiser,
I don't see any difference between on and off positions on the control
panel for the shaft alternator. Just pulling the 200 gallon water
tank....er, ah....6' fat keel...that's better...is draggin' her down to
make her comfortable. Noone is in a hurry on a Sharki...(c;

Larry
--
If electricity comes from electrons, does morality come from morons?

Hanz wrote:


Terry K wrote:
A technical subject requires technically correct language. One amp for
one hour is one amp-hour. 167 amp days is a convertible unit, but not
a conventional one. To correctly express amp-hours implies watt-hours,
but amp days implies a basic misunderstanding or mis-expression of a
conventional arithmetic term, since techs use amp-hours. 167 amps at
nominal 12 volts for a day is 48,096 watt-hours, a big wack of power,
unrealistic given the circumstances. 6 amps all day is 24 hours times
6 amps is 144 amp-hours. At 12 volts, that's 1728 watt-hours, or about
as much as a fully employed electric kettle needs, all hour, every
hour.

So, you could charge the battery all day, if it's big enough, and then
boil kettles full of water to boiling and discard the boiled water,
not counting invertor losses, for about half an hour, maybe 6 kettles
full. Overall, you only get back about half of what you put into a
battery.


Most of the power doesn't go into the batteries. It used to run the
freezer/frig, auto pilot and nav equipment. The left over power goes
into the batteries.


I can measure output of tow generator and also input/output of the
batteries.

The tow generator output 6 amp each hour for 28 days (from usa to europe).

We loss about 1/4 knots.

Hanz



That's pretty good!

Does your Ferris generator look like an electric outboard trolling
motor? What does it weigh?

Would a trolling motor put out that much? I don't know, and I'm not
gonna cut the wires to install a switch to try it out. If I did, I'd
consider a different prop for generator duty. A charge pumper would
help.

28 days*24 hrs*6 amps = 4043 amp-hr @ 13.5v = 54,432 watt hours.
Guestimate at just trickle charging a strong battery. Your nav gear
uses a little, your freezer/fridge sucks big time off and on.
Insulation and duty cycle determines charge discharge profile of
battery, estimate 10% on 90% off, using battery storage and suffering
it's inefficiencies. Did your battery require other input to keep up?

Consider cost benefit analysis of increasing insulation vs. increasing
generator power.

See http://www.otherpower.com/ for ideas about building serious output
generators from scrap, driven by a prop dragged by a steel cable
instead of a windmill. A person could probably get plenty of wind,
sail and water power if you don't mind slowing down some.

Terry K