Keith,
I'm pretty sure that the range values that he quoted were from his display. He didn't actually run the boat at 69A for 0.9 hours. He didn't indicate anywhere how far or how long he went at any given speed. AGM batteries are typically rated to allow a 1C load, in this case 100A would be considered acceptable. Alternatively, due to their higher internal resistance, flooded cells should be limited to discharge rates of less than C/3.
There are a few weird things about the data. When he changed directions going from a headwind to a tailwind, his amp loads went up for given speeds. That doesn't look right for any electric boat I've operated, including my dinghy with a Torqeedo.
As far as the unusually high draw for the given speeds, I would guess either the system is over-propped/under-geared, or the Sillette drive has a lot of parasitic drag in the driveline, or possibly a combination of both. Declaring a 14" prop is only half of that story, the pitch is important info to evaluate the system. We also don't know the overall reduction between the motor and the prop, from the Sillette drive and/or the coupling to the drive leg, another important piece of info. Sillette saildrive legs come in 2:1, 1.6:1 and 1:1 internal gear ratios.
I believe that the EY 100ibl is based on the Mars ME0907. The observed RPM seems pretty high for the speeds quoted, suggesting an overly high gear ratio, but that should reduce the amp load on the motor for a given boat speed.
Finally, we may be looking at incorrect data from the display, perhaps the amp loads quoted were not what we think that they are, sending us all on a wild goose chase. I know that the motor amps (AC) on my Sevcon Clearview display do not correlate directly with the load on the battery bank. We don't know if the speed data came from a knotmeter or a GPS, that can make a big difference if there is any current. The overall data comes nowhere near the typical "double your power to speed up 1 kt". The quoted data is very inconsistant so far.
As you can see, there are a number of possibilities to explain the reported performance, however, some additional information would be needed to zero in on what is actually happening.
Perhaps we'll get another report that includes more of the relevent data sometime soon.
Fair winds,
Eric
Marina de Rey, CA
--- In electricboats@yahoogroups.com, "aweekdaysailor" <aweekdaysailor@...> wrote:
>
> If the ammeter is correcting for Peukert they may be about right - you shouldn't pull more than about 25amps off a 100AH bank...
>
> But something else isn't right or the batteries would be completely drained after the first 69AH run...
>
> -K
>
> --- In electricboats@yahoogroups.com, "Capt. Mike" <biankablog@> wrote:
> >
> > Eric
> >
> > Sure sounds like something is not right with those amp numbers. I'm sure those numbers will greatly improve once you find where the problem is.
> >
> > Capt. Mike
> > Sent from on board BIANKA
> > http://biankablog.blogspot.com
> >
> > -----Original Message-----
> > From: erichmadison <no_reply@yahoogroups.com>
> > Sender: electricboats@yahoogroups.com
> > Date: Fri, 15 Jul 2011 21:49:32
> > To: <electricboats@yahoogroups.com>
> > Reply-to: electricboats@: [Electric Boats] first outing - commissioning
> >
> > I had the opportunity to take out and commission Coincidence, a Victoria 26 with an Electric Yacht 100ibl system paired with a Sillette saildrive and 100Ah AGM battery bank. I'm using a 14" prop.
> >
> > I wasn't overly thrilled--but mostly due to the nailbiting experience of trying to make it through a shallow channel to get to open water. It takes me a few times to get to know where the channel is each year, since the marker buoys aren't paced with any real accuracy.
> >
> > There was a 5-8mph headwind heading out. Here are some readings I took:
> >
> > KNOTS / RANGE / AMPS / VOLTS / RPM
> > w/ 5-8 MPH headwind
> >
> > 3.75 knots / .9hrs / 69A / 47V / 1770 RPM
> > 3.5 knots / 1.2hrs / 54A / 47V / 1750 RPM
> > 2.5 knots / 1.7hrs / 40A / 48V / 1530 RPM
> > 2 knots / 6.4hrs / 12A / 49V / 1000 RPM
> >
> > with tailwind
> > 3.75 knots / .9hrs / 69A / 47V / 1750 RPM
> > 2.5 knots / 1.6hrs / 43A / 48V / 1500 RPM
> > 2 knots / 5.7hrs / 13A / 49V / 960 RPM
> >
> > I made a slight adjustment then took these readings (still with tailwind)
> > 2.5 knots / 2hrs / 35A / 48V / 1330 RPM
> >
> > Overall, the motor ran smooth but seemed to be a little erratic at lower speeds (motor would rev up and down). Seems overly sensitive at certain spans.
> >
> > I haven't been able to bounce these off Scott yet. I'll share these with him next week to get his opinion. This one of the first few EY installations with the Sillette saildrive.
> >
> > The OEM engine was a 15hp, with effective hp probably closer to 10. I seem to be in that range with the new motor.
> >
> > See project blog at http://v26coincidence.blogspot.com/ --but I haven't posted the readings yet.
> >
>
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