GL: electric propulsion

[Bill Donovan]

Am I missing something here?

Some rough calculations...

If you assume the system is 24vdc (doesn't really matter whether it's 
12, 24, 32 or what), a 25,000# boat will need some about 55 hp to 
drive it at hull speed.  Let's say, for the benefit of the 
salespeople that you drive the boat at only 4 knots, and that only takes 25 hp.

Now, 25 hp is 18,650 watts, or 18.65 kw.  A 2000 watt Honda 
generator  would have to run a full 9 hours at full load to supply 
enough power to the batteries to provide power to run the boat at 4 
knots for ONE hour.  And, can you imagine a battery bank big enough 
to provide power for an afternoon's jaunt?  That's 777 amps for four 
hours at 24 volts.  As I recall, one 8D is good for about 450 amps 
for an hour or so?

I AM missing something!

Bill


At 03:30 PM 10/11/2007, you wrote:
>I just got a call from a friend attending a trade show.  He said he was at a
>booth where they are selling electric motors capable of pushing a 25,000# boat
>at speeds up to 8kts.  The boat has a large battery bank and two 50amp
>multibank chargers.  The chargers are run using a Honda generator which
>consumers about 1 gallon of gas every 8 hours.  Anybody have any thoughts
>about such a system?
>Tommy
>_______________________________________________
>http://lists.samurai.com/mailman/listinfo/great-loop
>
>To modify your Great-Loop subscription options (change email address,
>unsubscribe, etc.) go to: http://lists.samurai.com/mailman/options/great-loop