Hi Richard.
The power recommendation of 1kW/ton would indicate a 750W drive for your boat with 1500lb of displacement. That should provide speed up to 90-95% of hull speed based on your waterline length. You didn't mention the length of your proposed project, but if we picked 16' LWL, it gives a theoretical hull speed around 5.3kts or an electric speed a little less than 5kts. We also often observe that halving your power drops your speed about 1kt, so now your proposed full throttle of 350W should deliver about 3.5kts maybe a smidge more.
You proposed battery pack is 5.2kW (110Ah * 48V) and if flooded batteries, should have a usable capacity of 3.1kW to a 60% depth of discharge. That 3.1kW should last 8.4 hours with a 350W load (allowing for the Peukert's effect) giving you a range at 3.5kts of 29nm.
You can see in my analysis that I had to guess on the size of your boat and from that guess, estimate the watts to knots. I would bet that your performance, if properly propped should be pretty close, maybe even a little better. If the power-speed estimate is close, the range estimate for your battery capacity should be very accurate.
In any case, if you can accept the 3.5kt limit to your top speed, then your plan as stated seems very doable.
I hope that this helps,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, RICHARD JAMES <dick.james@...> wrote:
>
> .... Anyway my project is probably an order of magnitude smaller than what you people are doing (apart from the guy with the canoe) but here goes. I'm planning a day boat for some genteel cruising on the upper reaches of the Thames (ie non-tidal). About six hours cruising a day at three to four knots. The hull form is pretty close to that of an inflatable, flat bottomed, rounded sides. All-up weight of boat, four people, batteries, motor etc approx 1500lbs. 350W 48v motor powered by four 110Ahr batteries in series. The question I have is this - does this all sound reasonable or is it way out. I would very much appreciate some advice.
>
> Richard James
> London, UK
>
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