Brad, Fluke have an accessory called a current probe which will allow you to measure AC or DC current up to 400amps. It is battery powered, each jaw of the probe contains half of a magnetic core. The jaws clamp around a conductor allowing current measurements without breaking the circuit. A Hall sensor mounted in the gap in the core senses the magnetic field produced by the current being measured. An amplifier circuit generates an output signal of 1mv per amp. The probe is connected to the multimeter and the mv reading equals the current in amps. I am in the process of converting my motor to PWM. control to try and improve the range that my batteries will take me. I will post the results of my trial when they are completed. I am putting a photo of the probe and the PWM controller in the photos section if you are interested. Regards, Arthur. -
-- In electricboats@
<bradley.a.bates@
>
> Hi Arthur,
>
> Thanks for this. Could you tell me how you attach the Fluke 87 to the circuits to do those measurements. I am not well educated in electronics.
>
> Thanks!
>
> --- In electricboats@
> >
> > Hello Brad, my name is Arthur Wade and I am in South Australia. I have a Minn Kota 40lb Rip Tide and recently did some current draw and speed tests with this motor on my 15ft sailing dinghy. At slack water with the wind behind speeds were :- 2.7, 3.0, 3.9, 4.3, 7.0 km/hr. Current draw :- 8.9, 10.8, 14.5, 18, 32, amps. Into the wind which was blowing at approx. 20knts. Speed :- 1.3, 1.8, 2.5, 3.7, 5.3km/hr. Current draw :- 9.6, 11.5, 15.4, 19.0, 34.5, amps. Current was measured with a Fluke 87 multimeter and speed with a Garmin v GPS my battery bank consists of three 12v, 55ah. Exide deep cycle. I hope this is of some use to you. Regards, Arthur. -
> >
> >
> > -- In electricboats@
> > >
> > > 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)
> > >
> >
>
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