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