Eric,
I for one want to thank you for publishing your trials, the data is very useful for comparison, one of these days I hope to be able to contribute with my tests.
Dave K
From: Eric <ewdysar@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Mon, March 28, 2011 9:04:35 PM
Subject: [Electric Boats] Re: Measured performance - more data
Hi everybody,
I did another set of performance trials yesterday. I started at 12:00 noon, after the last rain shower passed. The process took about 90 minutes and I covered 6.35nm during the tests. I ran the same process as before, 1 pass in either direction at a particular throttle setting, progressively climbing through 6 settings and then repeat the process descending through the same settings until done. There was some wind by the end of the trials, but that should be offset through the pass in each direction. The results were more consistant than the last trials which had apparent tsunami surge that skewed some of the numbers.
Here's this weeks results:
495W = 3.0kts
1000W = 3.9kts
1500W = 4.5kts
2450W = 5.0kts
3905W = 5.7kts
5165W = 5.9kts
Slightly better at the low end and a little worse at the top end, but fairly close (+/- 0.2kts) to the previous tests.
Because we had a conversation in the interim about motor temperatures, I recorded winding temps during the second half of the trials to see how quickly the motor would recover during the lower power settings. With a max observed winding temp of 74C at the end of the fourth pass at full throttle, the motor dropped to 52C by the end of the last 500W pass.
Right after the trials, I set the throttle to about 2500W and headed out of the marina, around the detached breakwater in open seas and then back in. 45 minutes later, at a constant power setting, the motor was stable at 60C and I had covered an additional 3.85nm. Apparently, the speed boost downwind is greater than the penalty going upwind resulting in an average speed of just over 5.1kts.
After messing about for 30 minutes or so at slower speeds, I brought her back to the slip. The entire day was 10.9nm with a 4.0kt average. The battery meter showed 107.7Ah consumed. After 15 minutes rest, the battery bank was resting at 52.35V. 4 hours on the charger, and she was fully recharged.
In a couple of weeks, I'm going to try a range run on the open ocean at about 1400-1500W to see how the batteries match up against their specs. I'm predicting about 18nm at 4.3kts out of 6.4kWh of usable capacity, that should take a little more than 4 hours.
I know that all this info is more interesting to me, so thank you for your time...
Fair winds,
Eric
Marina del Rey, CA
--- 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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