Ben,
I'm going to take a few liberties with the data provided and say that your predicted performance might be:
4kts = 35A or 2600W
5kts = 65A or 4800W
6kts = 120A or 9000W
To my eye, the progression isn't quite right, I've seen with 30' 5 ton boats that each knot doubles the electric demand and a little more as you get toward the top end. This probably has to do with the propeller losing efficiency as the speed goes up. But these numbers are probably not too far off and close enough for this exercise.
I crunched some numbers for your 395Ah batteries using the predicted performance numbers listed above. I assume a depth of discharge of 60% and a Peukert's Exponent of 1.25. Here's the results:
4tks = 5.9hrs = 23.5nm
5kts = 2.7hrs = 13.5nm
6tks = 75min = 7.5nm
Honestly, this is not too bad. My target for my boat was 20 nautical miles at 4knots, and my boat exceeded my target by being able to do it at 4.2kts. Your boat looks like it is right there.
You may also want to reach out to a couple of other vendors to see what your drive choices are in the 10kW range. I think that it pays to shop around.
Not a bad start.
Eric
--- In electricboats@yahoogroups.com, Ben Okopnik <ben@...> wrote:
>
> Hi, Eric -
>
> .... Well, the estimate that I've got from EY is here:
>
> http://okopnik.com/misc/ibl360.pdf
>
> I suspect that it's way too optimistic (maybe a third to a quarter over
> realistic figures), but it's a start. Here's a series taken off their 72v
> chart in that PDF:
>
> 25A 3.4kt
> 50A 4.6kt
> 100A 5.8kt
> 150A 6.6kt
> 200A 7.3kt
> 250A 7.8kt
> 300A 8.3kt
> 350A 8.7kt
>
> (One of the things that makes me a bit skeptical of those charts is that
> my boat, fast as it is, surfs at about 7.5kt (36'9"LWL). Unless, of
> course, they're supplying free wings with the motor... :)
>
>
> .... Eric, I really appreciate the overview; as I said, this is exactly the
> kind of info I was looking for, since it allows me to start boxing in
> the possibilities. Thanks again!
>
>
> Ben
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