DC-182 solenoid problems

[RonR]

We have a lewmar 24v bow truster in the boat.
When we bought the boat the bow truster did not work. After replacing the block box and the DC-182 dual reversing solenoid it worked again! Fast forward one year and the DC-182 welded itself together again. I blame this failure on myself. Bad situation, over use of the bow truster.
I replaced the DC-182. It worked once again… used it about 10 times total. Min use, never for long, just a bump bump to place the bow on the dock. And now it’s failed again (5 months)
This time I was lounging on the boat. The truster came on by itself while the boat was off and tied up in the slip, nothing else was on or running., unit was not powered up with the controller, but did have the batteries in the on position. I went to the control head, powered the unit up. Still stuck on, so I went down and cut the power via switch. Pulled the DC-182 out and it’s welded together on one side again.

Lesson learned, never leave the boat with the power supply on. I have read this has happened before to a few others.

But why did this happen?
How can I prevent it from happening again?
And why does it weld itself together?
Unit is in a dry location, batteries are 18” away and test well.
No corrosion on the contacts.

 

[Comodave]

Maybe the solenoid is marginally big enough for the application. I would ask Lemar if there is any known issues and maybe they have a heavier duty solenoid. Agree on not leaving thruster batteries on. I had one come on when no one was on the boat too.

 

[Lepke]

Buy a higher rated solenoid or run 2 in parallel.


Is the thruster getting 24v while running? Watts stay the same, so if less than 24v, amps go up.

 

[ABfish]

Is it possible that you have a bad ground or undersized cables? That could increase current draw and create an overcurrent situation at the solenoid.

You should check the voltage at the thruster with the thruster activated. You should have at least 21 volts.

 

[RonR]

I contacted Lewmar… no return.
I contacted EV drives, and it looks like the unit I bought as a replacement is not the correct unit. So … my fault again.


“ Hi Ron,

The unit you bought from us was not designed for a bow thruster but for use on a golf cart. The bow thruster coils are rated to run only for a few minutes so that they will slam the contacts harder and also has oversize contacts.

Here is a unit that was designed by Albright and made by Albright for bow thrusters.
https://evdrives.com/original-albright-dc182-875l-reversing-contactor-24-volt-dc182-491-equivalent/

Things that could cause the contacts to weld are:

Weak batteries that are not holding up under load.
Bad switch that is lowering the voltage running to the coil of the contactor.
Motor brush that is failing so it is pulling to much current.
The blades not being clean and causing more load.
A motor that is failing which can cause too much load.
Small battery or motor cables that cause voltage drops.

Regards
Carl

 

[Comodave]

That is what I suspected. Glad you found something that should work.

 

[TowLou]

Put a master on off switch for the thrusters powered off the ignition circut with a relay so its only kicking on when the ignition is on.

 

[C lectric]

*****QUOTE*****
Here is a unit that was designed by Albright and made by Albright for bow thrusters.
https://evdrives.com/original-albrig...91-equivalent/

Things that could cause the contacts to weld are:

Weak batteries that are not holding up under load.
Bad switch that is lowering the voltage running to the coil of the contactor.
Motor brush that is failing so it is pulling to much current.
The blades not being clean and causing more load.
A motor that is failing which can cause too much load.
Small battery or motor cables that cause voltage drops.
******END QUOTE****

I looked at the reference and noticed they offer suppression diodes . THose would be a good item to order and install. DC motors will create a very high voltage and powerfull REVERSE voltage backflash when de-energized
or shut off.

THere is a lot of magnetic energy stored in the motor coils when operating and when shut down that energy has to go somewhere. Without the diodes that energy will jump and burn the contacts.
THe diodes allow the reverse voltage to run back through the motor windings to be dissipated as heat. THat backflash is of very short duration but if not dealt with will do damage to the control relay and can severely shorten the relay life.as you have seen.

Just a last note is that backflash can also damage electronic equipment if it gets into your general system. Long cables and Batteries will act to dissipate that energy also but better to dissipate it at the source.

When installing just be sure the installed polarity is correct. It must be installed in reverse polarity so the normal operating voltage is blocked.
There should be instructions with them for installation.