[PSUBS-MAILIST] amp gauge

Sun Jun 19 05:46:13 EDT 2016

Hank,Yes & No.If you have a constant load & you reduce the voltage, the amps willincrease. So increasing the voltage will reduce the amps on a constant load.It gets complicated because you are pushing your submarine, & there is drag to overcome.I have heard that you quadruple your energy consumption to double your speed underwater; so that would imply that if you were doing a certain speed at 12V & 10 Ampsthen you would have to be at 24V & 20 Amps or something like that, to double your speed.  If it were my motor & I couldn't find out what voltage or maximum amps it should be working off, I would be looking at other similar sized motors for a similar application with similar resistance in the windings, & using that as a starting point for tests. I would surmise that other motorsthat are enclosed in cans, like the minn kota, would have heavy windings & be de-rated because of the possible excessive heat build up in their worst case scenario. In your cold lakes you couldrun a motor at higher amps than if you were running it in a shallow lake in Florida.It would be good to have a heat sensor in them. Some thrusters come standard with heat sensors.So having estimated what you think the motor rating is, if your motor is not drawing enough ampsat full voltage, then you could try changing the prop.Another thing you could look at that might give you a clue, is the no load maximum rpm you aregetting at the varying voltages, & compare that with other motors.I am not an expert on these things (yet) but know it can be complex, & the best results are from testing& seeing where you get the best efficiency for the speed you want.Cliff may possibly like to weigh in with his findings from his Minn kota & variable pitch prop tests.Cheers Alan

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Sunday, June 19, 2016 12:12 PM
 Subject: Re: [PSUBS-MAILIST] amp gauge

Alan,If I increase the voltage, I will increase the rpm that should in turn increase the load.No? Yes?Hank 

    On Saturday, June 18, 2016 5:53 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Hank,the amps are proportional to the load. If the low amp draw iscorrect then a higher pitched or bigger prop would be the solution.Cliff has amp draw specs on the 101. If your motor is of a similarsize maybe you could aim at his amp draw rate! Alan

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Sunday, June 19, 2016 10:48 AM
 Subject: Re: [PSUBS-MAILIST] amp gauge

Alan,There is some mystery with the motors, we think they are 36v but the amp draw is to low.   I think I will bump it to 48 volts on my next dive.  They could use a bit more power i think. I tested them at 48v in the lake here at home and they seemed happy and very powerful to hold onto by hand.Hank 

    On Saturday, June 18, 2016 4:12 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Hank,no the voltage won't matter. The meter reads the voltage drop across the shunt.So at 7 amps per motor that's 250W each. What is the motor rating in watts?Are they the original propellers? Am thinking that if that is the correct amp reading& the motors are rated a lot more than 250W, then you could go with a bigger orhigher pitched propeller to put a higher load on. Alan

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Sunday, June 19, 2016 9:36 AM
 Subject: Re: [PSUBS-MAILIST] amp gauge

Alan,The amp rating is 100a  I am drawing 14a with both motors running.  They are not gear head motors.  Does the voltage matter?  Hank 

    On Saturday, June 18, 2016 3:23 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Hank,I have a couple of those external shunts & there is only a maximum amp rating printed on them.The voltage can vary depending on the state of charge anyway.What are you drawing at full power? Are the motors geared?Alan

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Sunday, June 19, 2016 2:15 AM
 Subject: [PSUBS-MAILIST] amp gauge

I am wondering if the amp gauge in Gamma is reading correctly.  Gamma was a 24v system and I have 36 v going through the amp bar and reading the amps from the original gauge.  Does the increased voltage impact the amp reading?Hank
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