I have a 12v Minn Kota 55 lb sitting unused. Dennis Wolfe is right about
the discrete speeds. The resisters are termed "Speed coils". I switched to
a Riptide 80 24v system using two batteries and a pwm controller on my Elver
and now have 3 times the range and much more endurance at low speeds. The
cost was about $600 vs $220 for the motor.
Will
On Sat, Sep 26, 2009 at 8:58 AM, cal29brad <bradley.a.bates@
>
>
> Hi Dennis,
>
> First, thank you to all who have replied to my post to date. I hope that
> more members will reply, especially to the specific questions regarding my
> calculations and the correction factors involved.
> ------------
>
> --- In electricboats@
> "dennis wolfe" <dwolfe@...> wrote:
> >
> > I bet your motorguide 54 is really a 34. There aren't 12v trolling motors
> that produce 54# thrust.
>
> This URL:
>
>
> http://sites.
>
> shows current 12V 54# models. Mine is slightly earlier model.
>
> Also, if you "Google" "12 volt 54 pound trolling motor" you will get many
> results. It seems that the manufacturers continue to push the envelope for
> thrust, which I like.
>
> >
> > If these have discrete speeds, like position 1 to 5 (max) forward and 3
> for reverse like my MK endura 36, you waste a lot of power running at
> anything less than full throttle. They cut speed by diverting part of the
> power to heat a resistor instead of turning the prop. You will pay 2-3x for
> a trolling motor with an efficient PWM speed control.
> >
>
> MotorGuide claims to have that type of control at the URL above.
>
> > I'm doing a lot of tests on an Endura 36 and can tell you mine draws 38
> amps with the boat tied to the dock and 32 amps moving at 4.5 mph pushing a
> canoe.
>
> This is something I do not understand. How do you and others measure these
> things? I am not an electronics engineer and am not schooled in how to do
> these things. Do you have any photographs, drawings or references that would
> explain the equipment needed to do this and how to correctly use it?
> >
> > The published amp hour ratings are for a slow draw that discharges the
> battery in 20 hours [ C20 ]. You will be discharging much faster than that
> so must derate the battery. Without getting into peukert exponent
> calculations, all you need to do is use the Reserve Capacity figure - that
> is how many minutes it will give up 25 amps. Figure on at most using 75% of
> this time as you are pulling more than 25 amps and the voltage drops off
> toward the end so you will slow down.
>
> Okay, that makes sense. Thank you.
>
> >
> > Denny Wolfe
> > www.wolfEboats.
> >
> >
> >
> > ----- Original Message -----
> > From: cal29brad
> > To: electricboats@
> > Sent: Friday, September 25, 2009 5:12 PM
> > Subject: [Electric Boats] Power Consumption for Minn Kota Riptide 50 &
> MotorGuide 54
> >
> >
> > Hello to All,
> >
> > I have a MotorGuide 54 that has these specifications:
> >
> > 12 Volts 0.34 Kwatts
> >
> > I also have a Minn Kota Riptide 30 with these recommendations &
> specification:
> >
> > 12 Volts
> > 105 Ampere/Hour Battery
> > "... your 12 volt motor with draw 1.0 ampere/hour ... for each pound of
> thrust produced when the motor is running on high."
> >
> > By my calculations these work out to:
> >
> > MotorGuide 54: (0.34 * 1000) / 12 = 28.33 ampere / hour
> >
> > Minn Kota 50: 1.0 * 50 = 50.0 ampere / hour
> >
> > Do those numbers look correct to all of you? The units and the pounds of
> thrust they produce are pretty similar, which makes me suspect the somewhat
> significant difference in the ampere/hour ratings.
> >
> > All enlightening efforts are greatly appreciated. I plan to use these two
> units to move a Cal29 sailboat about six to ten miles across (or down) Boca
> Ciega Bay to downtown St. Petersburg Florida early next week, and need to
> calculate what size batteries I should get. The boat is not refitted yet, so
> I need to jury-rig all of this, including battery locations, cabling,
> breakers, and so on.
> >
> > I have found a local firm that has what appear to be 85 amp/hr (they
> "rate" them thus: 205 minutes at 25 Amps each) 12 Volt deep cycle marine
> batteries currently on sale for about $60.00 each. Again, according to my
> calculations, three of those should give me either 2.5 hours (using the Minn
> Kota) to 4.5 hours (with the MotorGuide) of full speed motor use with about
> 50% battery consumption. Does that look correct?
> >
> > Thanks much in advance,
> >
> > Brad Bates
> > Play Mate
> > St. Petersburg, FL
> > (I am dangerous with a calculator)
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>
>
[Non-text portions of this message have been removed]
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