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Old 10-04-2019, 00:37   #16
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Boat: 50ft Custom Fast Catamaran
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Re: How is wiring for bow thrusters normally done?

That's good advice on the power windlass usage. I had been powering it down as well. Thanks again. I'll do it your way. Makes a lot of sense.

I have 2 boats. Deciding which one to keep currently. This one is a 50ft mono. The other a similar LOA Catamaran. This mono has 200' 3/8 BBB chain and 60lbs Manson Supreme as main anchor. The cat has an 80lbs Rocna. Never actually noticed a difference regarding the weight of ground tackle on a manual windlass. All about the same effort no matter what size anchor (chain is always about the same). I truly enjoy the simplicity.

I have this electric windlass on the 50' mono which is the one with all the issues:

It's the same brand and looks very close to this, but has a different topmost surface. It has a smooth top with 2 holes the size of a q-tip. I found these holes control a friction plate/clutch to release the capstan from the drive motor, allowing the gypsy to free fall the chain. It also has forward and reverse.

But absolutely no manual function. Not a fan.

When I found the batteries weren't holding a charge, i had to tie a line to the anchor chain and use a sheet winch to pull the chain up a small section at a time. Not fun.
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Old 10-04-2019, 01:34   #17
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Re: How is wiring for bow thrusters normally done?

Originally Posted by Pelagic View Post
This discussion comes up often with 2 schools of opinion.
1.... Centralise your House and Start Banks and charging systems, isolate with On Off and Emergency Parallel switch then run heavy cable to large loads of Thruster and Windlass with appropriate fuses/relays and Switches.

2.. Put seperate battery at bow and stern to be charged separately.

I favor #1 so that I have:
Better battery management, Centralized weight
More reserve and charge buffering if needed in a grounding emergency.

I think Cost of properly sized large cable is a one time cost, whereas individual batteries compromised by bow installation is an unnecessary and repeated cost of replacements as the OP is finding out.

Just my opinion though

With a 12 volt thruster you could be drawing up to 600 amps. The voltage drop from a centralized battery bank with a run of 30' or more would be significant and may result in damage to the thruster. It makes way more sense to install dedicated batteries at the point of use especially when they can be charged with a light wire providing 10 amps.

Our boats thruster was originally powered from the house bank. Those deep cycle batteries are not intended for high amperage draws and it is best to use cranking batteries for this purpose. After installing dry spiral cranking batteries for the thruster at the point of use we noticed a significant improvement in the thruster's performance.

Most modern chargers have a secondary charging circuit that can be used for charging a second battery bank or simply parallel them into the starter battery for charging which also gives you a back up starter bank. Obviously this would require a large cable run between the batteries but this is relatively cheap for the piece of mind.
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Old 10-04-2019, 07:55   #18
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Re: How is wiring for bow thrusters normally done?

If you want to trace your wiring lay out a cheapo extension cord along the cabin sole, from where the source/panel/control is, to the thruster location. An alligator clip lead onto thruster terminals (one at a time) lets you make a circuit via the extension cord and check for continuity with an ohmeter/multimeter working at the source end.
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Old 10-04-2019, 09:46   #19
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Re: How is wiring for bow thrusters normally done?

Originally Posted by sailah View Post
I'm in the process of rewiring my charging system. I spent a fair amount of time letting Maine Sails excellent schematic sink in. Down at the bottom he posted the schematic attached, I have studied it and plan to execute almost verbatim.

I swapped out my main battery switch to a Blue Sea that allows both start and house to be switched on, and if needed, to be paralleled in an emergency. But now all loads, except for the starter, are connected to house.

All my charging goes to my house bank. From this house bank, I run a Blue Seas ACR. When it senses 12.75V (or something like that) the relay closes and it parallels the banks for charging only. This way my engine start battery is isolated from all other loads and is charged when engine is running (or shore power or generator/solar which I don't have). The ACR will charge up to 120A I think.

I think if you study his diagram it will make sense and some appropriate ACRs to charge up your thruster batteries would make sense to me at least. If you want to get fancier with parallel switches etc might make sense to ask him about a paid consult to modify the diagram to your needs.
Excellent diagram... Bilge pump is wired incorrectly though. Bilge pump(s) and VHF should be wired so that an accidental incorrectly flipped switch cannot disable them. just move the feed for the pump to the battery side of that switch.
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Old 10-04-2019, 21:28   #20
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Re: How is wiring for bow thrusters normally done?

there is no normal way... there are many ways. you'll have to look and follow every wire and see how yours is wired. and determine if it is ok or not.

I've seen thurster banks directly connected to a house battery. (so one large bank with a 30' long jumper wire. and of course this wire never gets fused at all let alone on both ends. so it's super unsafe. and likely can't be fused big enough for the wire to not blow.

you can do it with acrs. but you'll going to see huge current. you'll still see 50% + of the thruster current through the acr wire. so you still need 2/0 or 4/0 wire with the acr. and fuse both sides high enought that it won't blow. at which point you may as well just scrap the thruster battery. the only way this works well is if you are able to shut the acr off while the thruster is engaged. to stop the high acr current while thrusting, but engauge it after for charging. you can use the acr SI port and figure out how to tap off the thruster controls to engage it. (both left and right, so you'll need diodes etc)

I've seen thruster banks with only an AC charger so it will only charge from a gen or shore power, never from an engine. this is not ideal. unless you are running the gen a lot.

the easier way is with a echocharger as the max current is always known and you can run small wire and fuses. the battery will drain while using thruster, and take a little while to charge back up. but it's not an issue unless you are using the thruster non stop.
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