Thruster Stopping

I have Sidepower bow and stern thrusters on a full keel Selene 53' trawler. The bow is used most often but the duration that it can run is unnerving. In about 1 1/2 minutes it will cut out from heat generated while using it. My thinking is since it is either fully on, or fully off their is a heavy load placed on the system that will drive up the amps needed to overcome a still prop to one that is turning. The operative word is fully on! Toggle on, toggle off seems to be the issue. Since it is a 24 volt system why not use an inverter to slowly ramp up the prop speed. Reduced lock rotor start is going to draw less amps and thereby create less heat. Problem solved since rarely is the full force generated is needed. HELP!!!

I think if you check the manual for it the duty cycle time is pretty short. Normal. Toggling off and on will definitely heat it up faster and wear out the contacts on the control solenoids. Once it is at full rpms it is the lowest draw it will ever be, inverter or not.

Without being rude, 1.5 minutes is a lot of time to be using a thruster and perhaps your handling technique could use a refresher from an instructor or a commercial operator?

A: if you run the thruster for a minute and a half while docking, either you're docking in a high current / wind area, or you're not using your boat & engine + rudder correctly. Thrusters are for helping you turn the boat, not to be used continuously to shove the boat around. Perhaps a little docking school might help you learn the way to not need the thruster that much.

B: you wouldn't want to run a thruster through an inverter due to the line loss. Every time you change it from one voltage, frequency, there is always line loss.

If you want to not draw as many amps and run it forever, get a hydraulic thruster for bow and stern. Hydraulics don't have the voltage drops found in electric powered hardware, but the oil does heat up when used for significant periods.

Let me clear this up a bit. The use is not continuous for a minute as a half. I toggle it on for 5-10 seconds, but over the 1 1/2 minutes of maneuvering it will overheat the heat sync.

there are no "rules" for proper use of a thruster...

one major use may be in emergencies that would exceed normal docking use as many dock without them at all.

Why does it cut out? Thermally? Could upgraded wiring or placing a power source closer help?

ditto psneeld. while 24 volt is better at longer runs than 12 volt its use can still over tax wiring. Years ago 32 volt was common in bigger boats. Running heavier wire may help or having a 24v battery setup closer to the thruster. Temporally moving 2 batteries close to the thruster and running it at the dock could prove or disprove the wiring theory. Otherwise it's the motor draw and components themselves.
I replaced all the 12 volt motors on most of my boats with Ac once inverters became cheap enough. I don't use a thruster.

Agree with the large size wire. Can you add some ventilation to the compartment that has the thruster? Side Power has a variable speed retro fit that may solve your problem. It will allow much longer run times.

jsbraga said:

I have Sidepower bow and stern thrusters on a full keel Selene 53' trawler. The bow is used most often but the duration that it can run is unnerving. In about 1 1/2 minutes it will cut out from heat generated while using it. My thinking is since it is either fully on, or fully off their is a heavy load placed on the system that will drive up the amps needed to overcome a still prop to one that is turning. The operative word is fully on! Toggle on, toggle off seems to be the issue. Since it is a 24 volt system why not use an inverter to slowly ramp up the prop speed. Reduced lock rotor start is going to draw less amps and thereby create less heat. Problem solved since rarely is the full force generated is needed. HELP!!!

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As I know it, thruster motor is akin to a starter motor on the engine, for all intents, electrically it's almost a short circuit ...... There is no inertia type load so it comes up to full speed instantly if anything, it will load up once it starts moving a volume of water. Most of them have an self re setting internal load / heat cut off. I would think that 15 - 20 sec. would be the most time that it will tolerate ...... my .02 CAD fb

I have a sidepower 12vdc 8hp on our 390 Mainship. I use it only sparingly (3-4 seconds on) and have never overheated; of course we're a much smaller boat. 1-1/2 minutes seems like a lot but i don't know your docking situation: wind, current, etc.
is the boat new to you? If so, maybe a call to the previous owner is in order to see what his duty cycle was. Also a call to Sidepower Tech to see if they have any options for you. Larger boat often use hydraulic thrusters to solve this issue.
good luck
John

Comodave said:

Agree with the large size wire. Can you add some ventilation to the compartment that has the thruster? Side Power has a variable speed retro fit that may solve your problem. It will allow much longer run times.

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Good point with the ventilation ! Re: wire size, I have a different view ie. Unlike a AC motor that tries to maintain it's rated HP,torque etc. regardless of voltage ( simply stated, will draw more amps if voltage is lowered ) , the DC motor will produce it's rated power according to the voltage that it's available. Eg. You can put a rheostat in series with a DC motor circuit, that will vary the voltage and motor speed ( incl. it's rated HP etc. ) therefore if you use a smaller wire size, that will create resistance - that will create a voltage drop - that in turn will reduce the rated power or speed of the DC motor ... and not it's current draw..... I think (?) ......... fb

When I was having issues with my 24v Sidepower bowthruster, it turned out that one of the two 12v batteries was shot. It would power up, but not at full power. Then, it kept blowing fuses. Anyway, after checking the batteries, and correcting the issue (2 new batts), the thing works like gangbusters.

Good luck, Bill

I would test it at the dock to see what’s really going on. I can’t believe it’s cutting out on thermal from 90 seconds of intermittent use. Either premature cutout setpoint or a battery problem.
Did the thruster work properly before and this is new bad behavior or has it always been like this?

Put me in the camp of suspecting an electrical issue. The Vetus thruster on my old Hatteras 56MY was 24 volt. It was powered by a bank of 2 8D commercial batteries which were about 6 feet from the thruster, no more than that. Cabling was 4/0. Spec was no more than 2 minutes running time in a session. That's a really long time using thruster. I had a couple or three dockings that combined wind, current and/or captain ineptness where we might have come close to that over the course of about 20 minutes of intermittent use. The Furuno nav system used the same bank and never went off or gave a low voltage warning.

I'd be curious what the battery bank and attendant cabling set up is.

Here is my analysis, which may be completely wrong, even if my logic makes sense.

Ohm's law applies. V=IR, and in this context, R refers to the resistance of the thruster motor and is very low (close to a dead short, as noted above), so I (current) is very high. It is the I that heats up the motor and does so, I believe in proportion to time and I. So, longer time or higher I heats it up and causes it to time out. If V drops, I must increase, thereby shortening your use interval without doing any more work. Thus, the goal is to make sure you are delivering full voltage to the motor. If its demands are reducing the voltage, you have either bad/inadequate batteries or bad/inadequate wiring from the batteries to the thruster. Either will reduce the voltage seen by the thruster. And for what it is worth, my 24v sidepower runs for way more than 2 min (continuous) before timing out.

Connect a voltmeter up at the motor and get someone to operate the thruster. You probably have a huge volts drop. If so munt 2 new batteries and cables up in the bow. Or run decent size cables$$$$$$

Check for a poor connection. Like MYTraveler pointed out, Ohm's law is at work. If you have a bad connection, it will restrict current flow. Voltage will drop, the thruster is now operating at something less than 24V but it still consumes the same wattage. SO... amperage is higher and the motor will heat faster. Thus it may time out on a thermal limiter.

Check the voltage at the thruster while it's operating. If it reads lots less than 24V, I'd be looking for a bad connection. Check every connection on both (+) and (-) sides of the circuit after the thruster has been run for a bit, look for warm or hot connections using an IR thermometer. That's a sure telltale. It is not enough to visually inspect the connections, a poor connection can look fine from outward appearance, yet be a problem. Could be a bad crimp on a cable. I'd suspect battery connections first.

There's also the possibility of a problem with the thermal limiter, it could be tripping lower than setpoint. But that would be suspect only if everything else is in good shape.

I'd bet dimes to donuts you have a bad connection. Somewhere.

MYTraveler said:

Here is my analysis, which may be completely wrong, even if my logic makes sense.

Ohm's law applies. V=IR, and in this context, R refers to the resistance of the thruster motor and is very low (close to a dead short, as noted above), so I (current) is very high. It is the I that heats up the motor and does so, I believe in proportion to time and I. So, longer time or higher I heats it up and causes it to time out. If V drops, I must increase, thereby shortening your use interval without doing any more work. Thus, the goal is to make sure you are delivering full voltage to the motor. If its demands are reducing the voltage, you have either bad/inadequate batteries or bad/inadequate wiring from the batteries to the thruster. Either will reduce the voltage seen by the thruster. And for what it is worth, my 24v sidepower runs for way more than 2 min (continuous) before timing out.

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That's correct, except it's worse because the heat varies as the square of the current I. So doubling the current quadruples the heat.

twistedtree said:

That's correct, except it's worse because the heat varies as the square of the current I. So doubling the current quadruples the heat.

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Thanks. I knew I was missing something, even if in the basically right.

Hi Jsbraga,

Many have suggested checking the usual culprits that cause electric bow thrusters to stop working during operation (poor connections, insufficient wire gauge from voltage source to thruster, low source voltage, etc.). These are the obvious culprits. Should you evaluate these (ideally with the help of a marine electrician), and not find any obvious faults, you may find that the thruster motor itself requires service.

The motor is a simple DC motor, irregardless of voltage. It has bearings, armature windings, brushes, a commutator, etc. ALL of these items can and will deteriorate should the motor be overheated, if the brushes are neglected, or the source voltage allowed to degrade, the motor allowed to get wet, and many other factors.

To service the motor itself, it should be removed from the boat and evaluated on the test bench of a competent DC motor shop. It isn't necessary to find a marine electrical repair facility, as it's fundamentally the same motor as a car starter motor. Service for DC motors can be found virtually anywhere.

Evidence of overheat on the motor is usually pretty obvious. The motor shop will megger the armature windings, inspect the commutator, inspect and/or replace the brushes, and also the bearings found on the motor shaft. They should also repair any burned or discolored insulation on the armature, and in general, return the thruster good as new.

As I'm sure you've perceived from the responses to date, many of the issues with bow thrusters are operator-related. The buggers are NOT intended for continuous use, and are equipped with thermal overload switches accordingly. And, if your boat's properly fused, you may find the fuses themselves speaking to you by blowing at inopportune moments.

Unless your Selene is a fairly new model, I'm pretty sure your bow thruster is simply bang-bang controlled. That is, 100% on/100% off. No modulation of voltage and/or current (other than that provided by Ohms law) is typically provided by the thruster controller. No issue, assuming the system is properly designed in the 1st place (probably just fine, as Selene typically does a good job on the initial design and install), and no issue if the bow thruster "system" is properly maintained, and no issue if the bow thruster is properly operated. But there probably aren't any simple fixes either.

Regards,

Pete

Archie: Long time Pal. Spotted Dog here! Have sold the Bert and now slow rolling it in Florida. This is a "new to me boat", but the seller did mention this issue before turning over the keys. It's definetly going out on thermal. Give it 5 minutes and she's good to go. The AGM batteries are fairly new (2014) but I have not load tested them. I do know that the generator needs to be running or things slow down fairly quickly. Somebody did mention about servicing the thrusters, but i'm not sold on that from the viewpoint of "what's their to service"?

Pete: I like the way you think! All you mentioned will be researched. I actually was looking at the ez way out that will not really solve the issue. Wires, connections, BRUSHES! YES, BRUSHES! Can't believe I didn't think of that because we sell DC powered machines with up to 250 hp. Looks like i'll be squeezing into tight spots soon.

Sounds like a conversation with the thruster manufacturer is in order.

I have a sidepower thruster that I converted from 12 volrs off the house battery to 24 volts next to the thruster. Here are some things to check:

As already mentioned:
Load test batteries
Check cable connections at batteries and thruster
What size cables and how long are they?
Check voltage drop at thruster. 15% or more will be a problem.

Have you checked the thruster propeller(s)? Fouled props will eat a lot more amps with less push. Is the tunnel clean? A fouled tunnel slows the push, requires longer duration, and requires more operating amps.

Ted

I need to clear up some stated misconceptions. A simple, series wound, brushed DC motor does NOT tend to overheat with reduced DC voltage. It does not act like an AC induction motor in this regard. Lower DC voltage, due to cable loss or battery drop will result in lower amperage draw. It will turn slower and produce less power.
Now, the use of larger copper wiring will tend to sink heat a bit, but I tend to doubt serious help will result.
At long duration 24V operation, the windings are simply running hot. You want either a larger motor, less duration, less voltage, less prop pitch, or better cooling. Is the motor totally enclosed with zero fan cooling??

diver dave said:

I need to clear up some stated misconceptions. A simple, series wound, brushed DC motor does NOT tend to overheat with reduced DC voltage.

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I would like to understand the physics (?) behind that, starting with why ohms law doesn't apply.

diver dave said:

I need to clear up some stated misconceptions. A simple, series wound, brushed DC motor does NOT tend to overheat with reduced DC voltage. It does not act like an AC induction motor in this regard. Lower DC voltage, due to cable loss or battery drop will result in lower amperage draw. It will turn slower and produce less power.

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And I may have been one of the promoters of that incorrect information, my apologies!! I was thinking from the perspective of AC induction motors where lower voltage means higher amp draw and greater potential to overheat. But as you point out, the DC motor we're looking at behaves differently. Thanks for setting the record straight!!

Next boat will have hydraulic thrusters. Contuous duty.

I have never needed more than 5 to 10 seconds on my stern thruster. It is rated for 3 minutes use. Don’t see need for continuous duty and the expense of hydraulic thrusters unless I hit the lottery and buy a Fleming 58 then all bets are off.

Isn't pulling up 150 feet of anchor chain rode just as taxing as using the bow thruster for a longer period of time? Maybe even more?? Do you guys pull up the anchor in short spurts and then rest? Or go for the glory?

When talking to the Mfg ask their opinion of max on time.

Many thrusters are short duration only.