Eric,
I agree, those numbers look real good for a 5 ton boat. Congrats.
Would you mind sharing your prop specs?
Jim
--- In electricboats@yahoogroups.com, "acsarfkram" <acsarfkram@...> wrote:
>
> Hi Eric,
>
> Those are excellent numbers! Do you remember what the voltage dropped to at 5170 watts?
>
> Mark
> Santa Cruz
> Not that anyone asked :-)...Lotus Flower survived the tsunami.
>
> --- In electricboats@yahoogroups.com, "Eric" <ewdysar@> wrote:
> >
> > So I finally got a chance to do some controlled performance trials over the weekend. I headed into the main channel of Marina del Rey at about 11:00 AM to measure system data while travelling a 400 yard course in opposite directions. Unfortunately, there appears to have been some residual tsunami surge that skewed some of the runs. From nearly no difference between the 2 runs to 1kt faster speed southbound, 1.4kt faster northbound 10 minutes later and 0.5kt faster southbound 15 minutes after that. So I'll have to repeat the tests sometime in the next few weeks.
> >
> > The boat is a 1964 Bermuda 30 ketch, 8'9" beam, 24' LWL and 10,200# displacement. The conservatively rated 5.5kW electric drive was purchased from Propulsion Marine in Santa Barbara. I assembled my own battery pack from 16 Thundersky 160AH LiFePO4 3.2V lithium cells for a pack rating of 8kWh @ 50V nominal.
> >
> > I measured pack voltage, motor RPM, southbound speed and average amperage, northbound speed and average amperage. Then I averaged the results for the 6 major speed settings. The pack voltage and current was measured with a E-xpert Pro HV battery monitor, and the speed was measured with a Garmin 60CSx GPS.
> >
> > But here's the quick recap of my boat at 6 different speed settings, 4 runs per setting.
> >
> > 500W = 3kts
> > 1000W = 3.8kts
> > 1475W = 4.3kts
> > 2460W = 5kts
> > 3910W = 5.7kts
> > 5170W = 6kts
> >
> > The funny thing is that my old diesel maxed out around 5.5kts at full throttle. While I don't intend to motor places at 5kw, it's nice to know that I've got the extra power if I get into a tight spot.
> >
> > The system worked great and now I get to re-work my range estimates for the better. This system exceeds my expectations, and I want to thank James for guiding me through the conversion. It has been a real partnership, again more than I expected. The only negative that I can see so far is that the new prop has more prop walk in reverse than the old one, so I've got to spend some time practicing backing down so that it becomes second nature again.
> >
> > That's it for now....
> >
> > Fair winds,
> > Eric
> > Marina del Rey, CA
> >
>
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