Reading amps draw on a trolling motor

[Beck]

Hi All,<br /><br />My son-in-law's trolling motor tripped his 50 amp circuit breaker last time we went out. I removed the circuit breaker from the circuit and it ran fine (we stayed on low speed and used it sparingly). I'm thinking the circuit breaker is bad. I am familar with ac voltages and amperages but dc is another animal. I have a dc ampmeter and voltmeter that I got at work out of an battery charger which circuit board went south. Ampmeter has 2 large terimals on the back. <br />Do I just wire the guage in series with the motor?I'm not sure what the guage goes up to but will check. And son-in-law has no idea how many amps it drew before. I did see a post but it included a shunt resistor? and was a kit. Well any input will be appreciated.<br /><br />Beck<br />

 

[rickdb1boat]

Re: Reading amps draw on a trolling motor

Wire the ammeter in series as you said or buy a clamp on amp meter. Either will work, even if it's for AC voltage..

 

[Sparkadelic]

Re: Reading amps draw on a trolling motor

Clamp on DC? Put it in series. Sounds like you know what you are doin beck.

 

[Beck]

Re: Reading amps draw on a trolling motor

Thanks Guys,<br /><br />Spark...Clamp on DC, sounds like that was news to you?<br /><br />Rick...I have the clamp around Amprobe oldie but a goodie, I never would have thought that I could read DC amps with that. <br /><br />I will try it and that way we will see if it's the breaker or the motor pulling excessive amps.<br /><br />Thanks again,<br />Beck

 

[wilkin250r]

Re: Reading amps draw on a trolling motor

As an electrical engineer, I cannot fathom how a clamp-on can read DC current, but then again, I didn't design it so I suppose it is possible

 

[cp]

Re: Reading amps draw on a trolling motor

wilkin250r - The DC clamp-on meters use Hall Effect sensors to measure the magnetic field generated by the current flowing in the conductor. As you know the magnetic field is proportional to the magnitude of the current, hence the Hall sensor output varies with the current also. Several companies make DC or AC/DC clamp-ons, Amprobe for one.

 

[Beck]

Re: Reading amps draw on a trolling motor

Hi to all,<br /><br />Ok, let me get this straight. To read amp draw on a dc line with a clamp on amp meter it must be a special one used for dc right? Not the oldie-but-goodie that I have. I have the one with the rotary scale that includes a voltage scale with plug in leads. I still have to get in touch with son-in-law to see if he has fixed the problem or had someone look into it for him.<br />Thanks for the input guys.<br /><br />Sincerly,<br />Beck

 

[cp]

Re: Reading amps draw on a trolling motor

Beck - Don't know which analog rotary scale Amprobe clamp-on you have but it most likely won't be capable of reading DC amps. As far as using the ammeter from the old charger, be sure you know what you've got. Some ammeters are actually millivoltmeters that require a shunt, while the internal resistance of in-line ammeters may affect the accuracy of the reading you get, and others may depend on a Hall sensor as mentioned above. The shunt or Hall sensor may still be in the charger.<br /><br />I don't know much about trolling motors, but looking at the Minn Kota specs, seems like many draw 40-something amps. In view of that, it's possible there is nothing wrong - maybe the motor momentarily snagged some weeds or something and a current surge tripped the breaker. Since you operated normally and no wires overheated/melted, the motor seems OK. My 2¢ is to try the old breaker again; if it still trips, install a new one. A replacement breaker would be cheaper than buying a DC clamp-on. If the new one trips, the motor or wiring may be bad, and then you'd have a spare breaker . Good luck.

 

[Beck]

Re: Reading amps draw on a trolling motor

Pchonda,<br /><br />Sounds like a plan, I'm going over to s.i.l. house in a little while to give him a hand with his camper. I'll talk to him about the trolling motor then. Thanks for the info.<br /><br />Later,<br />Beck

 

[Beck]

Re: Reading amps draw on a trolling motor

Update,<br /><br />I had a fluke multimeter and got the amp pluging adpt. can read dc amps and ac amps. My 40# Minn-Kota All terrain draws about 6, 9, 12, 16, 33, on the 5 forward speeds. The motor recommends a 50 amp circuit breaker, should it be a 40 or 45 amp c/b instead? To be closer to the actual amps?<br />Thanks for any input.<br /><br />Beck<br /><br />Ps: 5 th speed really cruises!! on my little flat.

 

[BassMan31]

Re: Reading amps draw on a trolling motor

My marine guy tells me that 40# and up should have a 50 amp breaker. I just replaced my 40amp with a 50 amp. My 40 was opening up but not tripping on #4 and #5 speeds. Just my opinion.

 

[Beck]

Re: Reading amps draw on a trolling motor

Bassman,<br /><br />Works for me I will be looking for a 50 amp c/b.<br />Son in law said his cost about $20 I saw them at here a little cheaper but then theres shipping.<br />There are several marine supplier here in town. Also a trolling motor shop.<br /><br />Thanks for the info.<br />Beck

 

[cp]

Re: Reading amps draw on a trolling motor

I agree with BassMan31 on using the 50A breaker. You don't want to size the breaker too close to the normal operating current because you might get "nuisance" tripping from momentary surges, like I surmised might be the case with your son-in-law's trolling motor (how did that end up?). Also, be sure to use the proper size wire; too small wire can cause a loss of voltage and poor performance. Judging by your ability with the multimeter and amprobe, I think you already know that but just in case, the Ancor website ( http://www.ancorproducts.com ) has a table of ampacities and also features a wire size calculator in their 'technical information' tab that you can use. Good luck.

 

[Beck]

Re: Reading amps draw on a trolling motor

Update on s.i.l. problem.<br /><br />When I checked his a/c out on his camper I asked about the trolling motor. He really didn't do anything but put the circut breaker back in line and start it while on the boat, not in the water. I told him I don't think you should run it out of the water they will overheat and you really don't get a true amp reading as there is no load. He's young and still learning. Since I now have the capability to measure dc amps, measured my new t/m yesterday, the next time we go out we will check his on all speeds.<br />My 40# tm draws 33 amps on high speed, I would think his 50# is getting close to 40 or so amps.<br />Any we actually hadn't gotten back in the water with his boat. Will let you know what we find.<br /><br />Beck