Bow thruster not producing much thrust

[O C Diver]

Took me a bit to come around to the current draw issue, but see that now. Vetus' page for this model includes an asterisk that notes "this model is design to be a compatible replacement for older Vetus BOW75 4.7kW units." Mine might draw more than 500 amps. No way that should be on 110 feet of 2/0 cable.

4.7 KW (4,700 watts) ÷ 12 volts = 392 amps. From recollection, a DC motor running at below rated voltage shouldn't require more amps, it should slow down.

Even more keen to know how much of a voltage drop you're getting.

I would consider taking your start battery up the the bow thruster and wiring it with some 2' cables as an experiment. See if it gives you the push that you want and how much of a voltage drop. Then all you have to do is decide how many boat units you want to invest.

Ted

 

[Jeff F]

If you have space for new batteries forward it's not a particularly expensive proposition. A couple of small starting batteries, a small dc-dc charger and a few short cables are all that's required.

My boat was wired like the OP's when I got it. This was one of my first upgrades.

 

[more]

I burned my bow truster from a factory installed on ex. boat. bow truster to battery bank be 5-meter cable 90 mm2. voltage on truster on work 9-10V factory. for you install 1 starter battery 100-180Ah around 1000+ cca 1 meter from truster and see a huge difference.

 

[Comodave]

4.7 KW (4,700 watts) ÷ 12 volts = 392 amps. From recollection, a DC motor running at below rated voltage shouldn't require more amps, it should slow down.

Even more keen to know how much of a voltage drop you're getting.

I would consider taking your start battery up the the bow thruster and wiring it with some 2' cables as an experiment. See if it gives you the push that you want and how much of a voltage drop. Then all you have to do is decide how many boat units you want to invest.

Ted

I suggested doing a temporary start battery for a test in post #12, I guess that great minds think alike…

 

[HeadedToTexas]

I will be doing the voltage testing this weekend, but I'm going to have to psych myself up to moving the main engine battery. That and eat some spinach. All in due time, of course.

In the meantime, the bottom diagram of these three is what I believe we are talking about. Both the thruster and windlass are currently powered from the house bank through the main busbar. The main engine and generator start batteries are only connected when the Auto Charging Relays meet their voltage requirements.

That bottom diagram shows the installation of new positive and negative busbars that connect the thruster and windlass to the main engine start battery. Both of those motors are behind switches and breakers or fuses, though my diagram only shows the switches. Is that an electrically sound and responsible way to accomplish the rewiring?

 

[O C Diver]

It looks ok to me, but I'm unclear where the alternator senses voltage to make sure both the house and start battery are full.

Ted

 

[DennisB1]

Important in this discussion is voltage drop at the wire to swaged terminal connection and from the terminal to motor post connection.
I wire brush to bright metal before crimping the exposed wire and the inside of the terminal the coat the wire with silicon dielectric grease before swaging. The grease provides a seal and provides a long term low resistant connect.
The connection at the motor post also needs similar treatment. That include the terminal surfaces, the post threads and the nut surfaces and threads. Again seal these with the dielectric grease.
Also the wire sizing and short runs are important.
My thruster is 24v with two group 31 agm batteries and about 6 ft total run with 2/0 cable works great.
The anchor winch is Lofrans 1500w 12 volt off the house bank. The alternator outputs over 100amps at 1100 rpm which makes a very noticable difference in winch operation versus battery only from a 1000amp hour bank.
Message keep all connection clean for best operation