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Old 08-05-2008, 09:42   #1
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24v bowthruster on a 12V system

I have a new 24V Side Power bow thruster…10” dia….I think its 340+- pounds of thrust that I would like to install.

My electrical system is 12V

My engine already has one dedicated alternator for the start batteries, and I plan on putting a second high amp (200) one on for the house bank.
Seems a bit odd to add a third 24V. Also I REALY want to keep the systems KISS.

Having said that, I do plan on having dedicated batteries at the thruster.

Has anyone had any experience rewinding (having rewired) a thruster motor?

Or any other reasonable ways of using it.

Any great Ideas.
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Old 08-05-2008, 10:42   #2
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Hi James,
For the same power, a 12 volt DC motor is going to be physically larger and weigh more than a 24 volt DC motor. I really think the best option is going to be to put two 12 volt batteries in series so you have 24 volts. It really does not make things that much more complex or any less reliable.

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Old 08-05-2008, 10:59   #3
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But how am I charging them?
I will have an inverter/12v charger.
I know I could take an AC 24v charger off the inverter but it seems like a lot of loss.
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Old 08-05-2008, 11:39   #4
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"But how am I charging them?"
Install a master switch, knife switch, or relay that will automatically or manually connect the two batteries in parallel for charging, in series for operation. That will also force the thruster to "local battery power only" when it is being used, and take it totally offline when those batteries are being recharged.
Considering the size of the cables you'll be switching, manually switching will be way less expensive.
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Old 08-05-2008, 12:10   #5
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See the Vetus #BPSPE Series / Parallel switch:
Products | Bow and Stern Thrusters | Vetus Products | UK
and:
http://www.vetusweb.com/manuals/file...01%2010-07.pdf
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Old 08-05-2008, 12:14   #6
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Quote:
Originally Posted by hellosailor View Post
"But how am I charging them?"
Install a master switch, knife switch, or relay that will automatically or manually connect the two batteries in parallel for charging, in series for operation. That will also force the thruster to "local battery power only" when it is being used, and take it totally offline when those batteries are being recharged.
Considering the size of the cables you'll be switching, manually switching will be way less expensive.
that is the set up I have for a 24v anchor windlass......works well....have a breaker to switch on and the windlass is energized....

Bill
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Old 08-05-2008, 12:14   #7
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I hadn’t thought of a manual “change-over “ type switch to switch the batteries from sequence to parallel….interesting.
If the switch is to be conveniently located (not in the bow), then there is no more advantage to having the batteries in the bow.
It’ll be a bunch of cable, but may be the solution I’m looking for.

I need to find a pencil and do some schematics.

Thanks hellosailor
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Old 08-05-2008, 13:21   #8
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Thanks for the links Gordmay

I’ll have to see how these switches operate.

Any one out there ever use them?

I must say I’m a bit partial to a manual switch, but don’t see how to avoid a lot of wire.
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Old 08-05-2008, 13:23   #9
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save weight

Save the excess weight of batteries in the bow. Put them where good for the boat and run the requisite cables to the thruster. Save the price of the excess wiring and switches to put into a 12V to 24V switch-mode converter like the following to charge the batteries:
*12V-24V Converter, 5A - Samlex Switch Mode- Step Up Converters
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Old 08-05-2008, 13:44   #10
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Thanks Rick
$409 is'nt cheap but it's cheap enough to be worth looking into.
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Old 08-05-2008, 13:53   #11
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You may want to rethink that 200A alternator in addition to your existing. That kind of side load on your engine bearings will reduce engine life on typical sailboat diesels. This can be handled with a more complicated pillow block installation but don't just slap an alternator of that size on without accounting for the side loads.
I would be more inclined to keep the batteries up front as 2-300lbs of weight in the V berth of your sixr boat will not be an issue and you can use smaller, shorter cables. While you need high current for thrusters...you typically will not use a lot of amp hours in total and a small 24V charger working off your AC system would seem to me to be an easy solution. (Though the manual system suggesed above will work fine too. )
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Old 08-05-2008, 13:55   #12
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I’ve never used the Vetus 12-24V switcher; but have manufactured my own; which. I’d guess cost me something on the order of $600 in parts, plus 4-5 hours labour.
Rick’s converter seems a more elegant solution, and cheaper to boot.
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Old 08-05-2008, 14:46   #13
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Just tap 2 12's to make 24. Don't add batteries to the bow, you will only run the bt when docking and the engine is running. We have 12 and 24 v systems and do not run the bt enough to run the 24 v bank down even a little.

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Old 08-05-2008, 15:09   #14
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What engine do you have?
Depending upon your setup you may be able to replace a front motor mount with a custom welded design that enables you to place the large frame alternator's mass over the mount which does not cantilever off of the engine attachment bolts when installed.

Regardless, I have done it both ways with no problems on the front bearings. With a large frame alternator at close to 200A output you wind up pulling about 7.5 Hp (depending upon the brand) from the engine using dual belts. A serpentine belt is even better if you can make the installation. Wonderful for charging those house batteries fast.
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Old 08-05-2008, 16:16   #15
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If you decide to go the 12v-24v transformer route (which should work fine and certainly meets your KISS requirement), consider Victron Energy's Orion units. Specifically the "12/27" unit that puts out 27 volts instead of 24 to adequately charge your thruster battery. I paid just over $100 for a different model Orion last year (although that was when the US dollar was still a major currency). If you haven't used Victron equipment before, you'll be impressed by the quality.

http://www.victronenergy.com/upload/...5000-D-cEN.pdf

Carl
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