At 10:58 AM 23/03/2010, MarkH wrote:
>Hello to all. I bought a Catalina 30 3 years ago, <snip>
>2) BUT, my concern is how this will work when I cruise up the
>canal from Elizabeth City North Carolina to Portsmouth Virginia, a
>50 mile, 8 to 10 hour journey - can I do this with electric
>propulsion?
>conserve amps; one must keep up 5 knots or so, to make the lock
>schedule, and to keep out of others way coming up behind you in the
>relatively narrow canal.
>
>In other words, can one feed charging juice to the batteries with
>either solar, wind, and/or generator while still moving at 5 knots,
>without stopping to recharge, making it possible to make a 50 mile
>trip at full speed non-stop?
G'day Mark
The way that range extending works is this: You may have (for
example) a 48 volt, 440 amp-hour battery pack (16 x 220Ah 6V in
series/parallel) which will let you have approximately 50 amps for
six hours (the slower you pull the amps out of a lead-acid battery,
the more available energy there is) giving you 50A x 48V = 2.4kW
which would probably give you 3 knots or more (guessing here) for six
hours - 18NM (your specific situation will vary). Your system would
probably be designed to give 15 kW or more, peak, (probably a 400A
controller, 19.2kW, which would give about 175 amps, 8.4kW, continous
which would be more effective power than you have now.
You may find that 5 knots needs 100 amps, or 4.8 kW, so you'll need
to find not only an extra 50 amps, but after 6 hours you'll need 100
amps. Only if you can find 75 amps from a genset, straight from the
get-go, you'll only be pulling 25 amps from the batteries which would
probably give you over 15 hours from the batteries. (Solar and wind a
great for recharging a battery but expensive to use for power as you go).
This is called "series hybrid" operation, where you are taking
mechanical power, turning it into electrical power, then back to
mechanical power again. If you can find a (say) 8hp diesel that you
can connect to the propshaft as well as the electric, you can run
both when you are needing to travel long distances, but just the
electric when you are needing short distances or manoevering. You
would not even need to reverse the diesel, so potentially a belt
drive reduction and mechanical dog clutch - when you are going to
travel long distances, after you've finished manoevering, stop,
engage the clutch, rev up the electric to start the diesel, throttle
up the diesel and back on the electric and off you go. That would be
a "parallel hybrid".
Series hybrid is what you'd do if it were a once-a year thing,
especially if you have use for a 5kW+ generator in between whiles.
It'd use about twice the fuel as a parallel hybrid, but may be less
hassle. If you're looking to do this kind of trip several times per
year, then parallel hybrid will be the way to go.
As much as anything, it'll depend on what your skills are, or have
readily available. Electric drive is really easy to do, with a bit of
mechanical/ machining skills, and basic electrical knowlege and
common sense. You may be able to find a big 'ol forklift 48V charger
cheap that'll give you your power conversion, hire a 10kW genset for
your occasional trips.
You're showing common sense in asking before you get into it and find
it doesn't suit your needs, so kick options around and see what comes
into shape.
Regards
[Technik] James
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