Bud, could you go into more detrail on this because I'm having a hard time understanding how you used more amps at 48V than 24.
Thanks, eric SV Meander
--- In electricboats@yahoogroups.com, Bud Elkin <bud.elkin@...> wrote:
>
> I'm running 24 volts on my houseboat because it used more amps at 48 volts.
> Although it runs slower, I can run forever as long as the sun is out. Every
> motor, and every boat is unique. Finding the best volts/amp/speed ratio is
> more than less experimenting with your system until you are content.
>
>
> On Thu, May 30, 2013 at 10:22 AM, oak <oak_box@...> wrote:
>
> > **
> >
> >
> > John (other John...),
> >
> > Thanks for your response - it's good to hear that the Torqeedo 2 will work
> > well for that size boat!!
> >
> > Eric or someone had explained in previous a previous thread how a 48V
> > system would be more efficient and better on battery life than a 24V
> > system. But given the doubling of effort on the battery side, I think I'd
> > compromise the power efficiency to be able to afford better batteries and
> > charging.
> >
> > If I can get some data on the Catalina 22 with the Torqeedo 4, it would be
> > really neat to see if we could correlate that to data on you Capri 22 with
> > the Torqeedo 2. (which would also be really neat to compare to trolling
> > motor data, if anyone had one...)
> > Wouldn't it be nice if you could RENT these things for a week and try them
> > out before putting down the $$!!
> >
> > Thanks again for the encouragement.
> > John (in Texas)
> >
> > ------------------------------
> > *From:* John <johnpomer@...>
> > *To:* electricboats@yahoogroups.com
> > *Sent:* Thursday, May 30, 2013 7:35 AM
> > *Subject:* [Electric Boats] Re: Trolling motors ==> electric outboards
> >
> >
> >
> > I have been using a Torqeedo Cruise 2.0 on my Capri 22 for the past two
> > seasons - the last season was on a mooring with only solar recharging. I
> > had tried a Minn Kota Endura 50. With a 4 inch pitch, it was insufficient
> > to maneuver the Capri in wind. (It worked fine for my O'Day 19 which has
> > half the weight.)
> >
> > When looking at the power output, Torqeedo uses "power at propeller"
> > (including all of the drive train losses), not shaft power (which neglects
> > power losses after the engine shaft).
> >
> > The Torqeedo performed as well as the Nissan 5 HP (2-cycle) that came with
> > the boat. Low speed and reverse are much better using the Toqeedo. I can
> > reach hull speed with the Torqeedo.
> >
> > Battery system is 4 GC2 lead acid batteries with a 100 watt solar panel
> > and a Genasun GV Boost MPPT charge controller (takes the nominal 12 vdc
> > from the solar panel and intelligently charges the nominal 24 volt battery
> > bank. Always had a full charge when leaving the mooring twice a week.
> >
> > John
> > (NOT aka "oak_box" <grin>)
> >
> > --- In electricboats@yahoogroups.com, oak <oak_box@> wrote:
> > >
> > > Eric,
> > >
> > > While I can "intellectually" appreciate the wisdom of all that you're
> > saying, my pocketbook doesn't want to hear it...<grin>
> > >
> > > Seriously, I get what you're saying, and it makes a lot of sense.
> > > You make a good point about the sizing of the props on the trolling
> > motors. I can tell you that the prop on my Torqeedo 4R is BIG compared to
> > any trolling motor, and definitely even any kind of outboard up to the same
> > size. If you believe the Torqeedo literature, they specifically designed
> > the prop on that motor for the electric outboard application, and it seems
> > to do a good job (though I'm anxious to get more experience with it).
> > >
> > > This afternoon, I came across the Minn-Kota Riptide that has dual motor
> > units and is rated at 160 pounds thrust - close to what the Torqeedo 4R is,
> > and at 24V (I didn't see anything that listed how many amps it would draw).
> > >
> > > At 1/2 to 1/3 the price - it's very appealing.
> > > But again, your points about prop size, motor speed, etc, are all well
> > taken.
> > >
> > > I happen to already have the Torqeedo 4R that I will experiment with on
> > the C-22. But if I could afford to get down to a 24V system instead of a
> > 48V system, it becomes much more reasonable to get a single 24V lithium
> > pack than to have to buy two. If only money weren't an object.
> > >
> > > The unfortunate reality there is that I can easily spend 3x the price of
> > the boat on the outboard and batteries!
> > > So yes, there are tradeoffs to be made And fortunately - in MY case - I
> > don't have to go terribly far on battery power. It would be really nice to
> > be able to cruise 2-3 hours. Typical case (at least if I was sailing) would
> > probably be 30 min. to less than an hour, and a good amount of that could
> > be at reasonably low power.
> > >
> > > I really wish I had the spare disposible cash to buy one of each of
> > several and try them all out! If the 80 foot pound motor was enough to
> > push the boat around a little bit, it would be fun to have the Torqeedo 2.0
> > as the main engine, and the trolling motor in a locker as a backup. Then
> > it would be fun to have the 24V lithium as the main battery, probably with
> > two cheap FLA batteries as a standby bank that I knew would get me at least
> > 30-60 min at low speed to get me home if I exhausted the primary bank...
> > >
> > > I need to buy more lottery tickets...
> > >
> > > John
> > > (aka "oak_box", but not really - just John.)
> > >
> > >
> > > ________________________________
> > > From: Eric <ewdysar@>
> > > To: electricboats@yahoogroups.com
> > > Sent: Wednesday, May 29, 2013 8:28 PM
> > > Subject: Re: [Electric Boats] Trolling motors ==> electric outboards
> > >
> > >
> > > Â
> > >
> > > Hi Oakbox (?),
> > >
> > > Yes, that amount of power should put you in the ballpark. Unfortunately,
> > trolling motors are made for ummm.... trolling, so they are rarely propped
> > for the speed that you are looking for. Making this work better may be as
> > easy as finding the right propeller, but some have found that even then,
> > the motor isn't built for the particular loading that you would be
> > imposing.
> > >
> > > So a Torqeedo 1003 at 1kW (40A @ 25V) would probably be just a bit
> > underpowered, but propped way better for what you want. I would predict
> > that a Torqeedo 1003 would be at least 1 mph faster than the Minnkota while
> > using 30% less energy. A Torqeedo Cruise 2.0 would have a bit extra power
> > (but probably not enough to push you all the way to hull speed). Though I
> > haven't performed the experiment myself, I would guess that Torqeedo motors
> > use half the energy as the Minnkota that you're looking at to push the same
> > boat the same speed.
> > >
> > > And Minnkota's range estimates are very optimistic. A 24V 100Ah battery
> > has 2400Wh of rated capacity. That's at the 20 hour discharge rate of 5A.
> > But as you raise your discharge rate, the amount of usable energy falls
> > off. Do a quick search on Peukert's Effect to find out how that really
> > works. Once you can accept the losses due to Peukert's Effect exist, I can
> > tell you a bit more about what your proposed battery can do.
> > >
> > > With a 2.4kWh 24V flooded lead acid (FLA) battery, a 56A load will drain
> > it 100% in 58 minutes, assuming a Peukert's exponent of 1.25. We also know
> > that draining a battery completely is not good for it, so most boaters will
> > limit their depth of discharge (DoD) on FLAs to 60%, actually most cruisers
> > will stop at 50%. Using the same 56A, you'll hit 60% DoD in less than 35
> > minutes. You would need 155Ah of rated capacity to run a 24V FLA battery
> > down to 60% DoD at 56A for 60 minutes.
> > >
> > > But AGM batteries are better due to their lower internal resistance. You
> > can run them down to 70% DoD on a regular basis. A typical AGM Peukert's
> > exponent (PE) is 1.1 and now you only need 105Ah of rated capacity to run
> > the motor at 56A for 60 minutes. So in my opinion, AGM are well worth the
> > money for electric drive traction batteries.
> > >
> > > What about lithium? They discharge to 80% and have a PE of 1.03. You
> > only need 77Ah of rated capacity to support a 56A load down to 80% DoD in
> > 60 minutes. They're pricey, but for some, well worth the premium. Let's
> > summarize the results.
> > >
> > > We want 60 minutes of 56A at 24V:
> > > FLA to 60% DoD = 155Ah = 165 pounds
> > > AGM to 70% DoD = 105Ah = 125 pounds
> > > LiFePO4 to 80% DoD = 77Ah = 50 pounds
> > >
> > > That's right, the lithium pack can do the same work with half the rated
> > capacity and less than 1/3 the weight of FLA.
> > >
> > > I said earlier that a Torqeedo can probably push your boat at the same
> > speed using half the energy as the Minnkota. If you could cruise at 28A
> > instead of 56A, this is what it looks like.
> > >
> > > We now want 60 minutes of 28A at 24V:
> > > FLA to 60% DoD = 77Ah = 82 pounds
> > > AGM to 70% DoD = 52Ah = 62 pounds
> > > LiFePO4 to 80% DOD = 38Ah = 25 pounds
> > >
> > > How much effect do you think that 140 pounds of un-needed weight
> > (Minnkota with FLA compared to Torqeedo with LiFePO4) will have on your
> > boat? How much does a Minnkota with two 155Ah FLA batteries cost compared
> > to a Torqeedo with a 20Ah battery built in and an extra 20Ah battery to
> > bring your range up? What is your sailing performance worth? My first boat
> > was a Catalina 22, I would probably step up and buy a Cruise 2.0 and a
> > separate 40A 24V LiFePO4 battery, but that's just me (see my signature).
> > >
> > > We can see that there is more to converting a boat to electric drive
> > than simply wiring batteries to a motor to drive a prop, regardless of what
> > James was thinking in his other thread.
> > >
> > > If you have any additional questions, feel free to ask.
> > >
> > > Fair winds,
> > > Eric
> > > 1964 Bermuda 30 ketch, 5.5kW Propulsion Marine drive, 8kWh Lithium
> > batteries
> > > Marina del Rey, CA
> > >
> > > PS I'm not a professional electric boat guy, just a hobbyist. I've
> > always thought that this is the kind of conversation that this group excels
> > at.
> > >
> > > --- In mailto:electricboats%40yahoogroups.com, oak <oak_box@> wrote:
> > > >
> > > > Ok, so at 50 amps * 24V, I'd be in the ball park for a 2300# Catalina
> > 22.
> > > >
> > > > From a youtube review of the Traxxis MinnKota 80# motor, they report:
> > > >
> > > > slow5A20hr
> > > > med28A3.6hr
> > > > top speed56A1.8hr
> > > >
> > > > The above assumes a 24V, 100AH battery.
> > > >
> > > > If I could get ~5mph out of a $600 motor for an hour, I'd be THRILLED!!
> > > >
> > > >
> > > > ________________________________
> > > > From: Eric <ewdysar@>
> > > > To: mailto:electricboats%40yahoogroups.com
> > > > Sent: Wednesday, May 29, 2013 5:00 PM
> > > > Subject: Re: [Electric Boats] Trolling motors ==> electric outboards
> > > >
> > > >
> > > >
> > > > ÂÂ
> > > > Hmmm. If there was only some way that one could easily estimate how
> > much electric drive would be needed to move their boat at 90-95% of
> > displacement hull speed....
> > > >
> > > > Oh yeah, back when we used to discuss boat conversions, the rule of
> > thumb of 1kW of power for each ton of displacement has proven to be correct
> > for boats ranging from 18 feet past 40 feet.
> > > >
> > > > Of course, one can move the boat with much less power (search this
> > list for "Jack LaLanne" for low power examples), but for safe operations in
> > all but the most extreme cases, this "rule" works surprisingly well.
> > > >
> > > > Fair winds,
> > > > Eric
> > > > Marina del Rey, CA
> > > >
> > >
> >
> >
> >
> >
> >
>
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