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Old 06-16-2015, 07:51 PM   #21
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Originally Posted by SCOTTEDAVIS View Post
Just a note, check if the cable used for the BT is the size required by the manufacture of the BT.

The length of run is the total round trip not just one way and often I see builders think this as a good place to save a few bucks as wire of the required size is not cheap.

With any amount of run you will want AWG 2 as the smallest wire for a small (4 or 5 hp) BT (mine came with awg 4) most larger units and you are into heavy cable 1/O or 2/O perhaps even larger.

When I put in awg 2 from the 4 it was like a new thruster. I was also cheaper then adding a battery and charging system, and no maintenance.
This....My wiring is as big as my thumb... No shut down or thermal issues whatsoever..
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Old 06-16-2015, 07:58 PM   #22
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I don't think it is a wiring problem with your thruster. If anything, inadequate wiring will reduce the current flow. Your electronics are shutting down because the voltage at the battery is getting too low because there is too much current demand, not too little. I am back to my original suggestion -- your batteries are weak, either under charged (verify that they are reaching full charge and that you have this problem when fully charged) or worn out (ie, significantly impaired capacity). You can confirm battery capacity with a load test. If they are proven bad, and if you have the facility, try equalizing them. Otherwise, I bet everything will be back to normal as soon as you replace the batteries. For what it is worth, lots of boats don't have a separate bow bank for the thruster and work just fine.
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Old 06-16-2015, 08:49 PM   #23
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The best batteries for DC thrusters are thin plate AGM batteries, such as Odyssey's or Die Hard Platinums (the same battery with a different label). They are capable of supplying tremendous amounts of current for short periods, which is just what a thruster needs. I have two of these (Group 31) in series to run a 24 volt thruster. The batteries are right next to the thruster, so there is no voltage drop through the short 0000 cables. The whole thing is charged with a Sterling DC->DC charger and it works like a charm.
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Old 06-16-2015, 10:24 PM   #24
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I have 3 of the Diehard Platinum group 31 in my start/thruster bank. Works very well with bow and stern thrusters going at the same time.
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Old 06-17-2015, 12:22 AM   #25
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Capttug, is your boat a Mainship 430 aft cabin trawler?
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Old 06-17-2015, 06:21 AM   #26
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I had the same issue a couple of years ago. It was addressed at TF here: Power for electronics during engine start

And here: DC-DC Converter

Basically you might want to consider a DC to DC converter for your electronics or a dedicated battery for your electronics. A dedicated battery for your electronics has the advantage of allowing you use of all the batteries on your house bank for the thruster which should make the thruster more realiable. A dedicated electronics battery would be a lot easier to wire just requiring a charging wire from your house or engine start bank with a diode.

I choose to just turn off the electronics before starting the engines, it's now habit so no problem.
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Old 06-17-2015, 08:58 AM   #27
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I don't think it is a wiring problem with your thruster. If anything, inadequate wiring will reduce the current flow. Your electronics are shutting down because the voltage at the battery is getting too low because there is too much current demand, not too little. I am back to my original suggestion -- your batteries are weak, either under charged (verify that they are reaching full charge and that you have this problem when fully charged) or worn out (ie, significantly impaired capacity). You can confirm battery capacity with a load test. If they are proven bad, and if you have the facility, try equalizing them. Otherwise, I bet everything will be back to normal as soon as you replace the batteries. For what it is worth, lots of boats don't have a separate bow bank for the thruster and work just fine.
Inadequate wiring will increase the current draw as the wattage of the load is not changed and you will increase the draw by heating up the wiring while reducing the voltage to the motor (still requiring the same wattage draw) thus drawing more from the battery's.

It has been stated correctly that BT's should be wired to the starting battery's not the house as they are like a starter, demanding a high current draw for a short time, not what deep cycle battery's like to do.

Too small of a bank of brand new deep cycle battery's may not be able to provide the short term current requirements as the surface area of the plates is to low to provide the burst needed even fully charged and new.

The real difference between starting and deep cycle batteries is starting has more thinner plates giving a greater surface area for more current (more conversion area) in the short term. DC have thicker (denser) plates but less of them (given same size as starting) for longer low current production as their deeper lead plates provide more (slower but longer) chemical reaction between the water/acid conversion.

The BT and windless is mostly used when the engine is running so the higher voltage provided by the alt. actually reduces the in-use wire size amount by 15% so is a bit of a bonus (14.8v is 15% greater then 12.6v).

BT should be on starting battery's as well as the windless or a separate starting battery not on house or deep cycle.

BT must be wired with the proper cables or larger and all connections must be perfect and clean.
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Old 06-17-2015, 09:02 AM   #28
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Originally Posted by timjet View Post
I had the same issue a couple of years ago. It was addressed at TF here: Power for electronics during engine start

And here: DC-DC Converter

Basically you might want to consider a DC to DC converter for your electronics or a dedicated battery for your electronics. A dedicated battery for your electronics has the advantage of allowing you use of all the batteries on your house bank for the thruster which should make the thruster more realiable. A dedicated electronics battery would be a lot easier to wire just requiring a charging wire from your house or engine start bank with a diode.

I choose to just turn off the electronics before starting the engines, it's now habit so no problem.

Tim, did you ever get that unit to work for you?
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Old 06-17-2015, 10:21 AM   #29
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Tim, did you ever get that unit to work for you?
No I did not. I did not properly troubleshoot it sufficiently to determine the problem as I had a laundry list of other issues to deal with. I will eventually get back to it.
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