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post #1 of 19 Old 11-18-2013 Thread Starter
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Bow thruster - dedicated battery bank cabe

I am about to install a forward battery bank to run a windlass (120 Amp max) and eventually a bow-thruster (300 Amp max). The forward bank will be 160 AH.

I will have the forward bank connected to the house bank (800 AH). The cable run is 15ft (30ft round trip). The house bank is charged directly from the engine alternator (120 Amps). The engine will be running when I am using the bow-thruster.

Logically I should expect 300 amps to run between the house bank and forward bank when the bow-thruster is running. Is this correct, or have I missed something?

Thanks

Gerry



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post #2 of 19 Old 11-20-2013
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Re: Bow thruster - dedicated battery bank cabe

I'm a fan of having a dedicated battery(s) for the foredeck equip. Not sure why you would want to interconnect them to the house batts? Seems to defeat the purpose.
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post #3 of 19 Old 11-20-2013
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Re: Bow thruster - dedicated battery bank cabe

I wouldn't install a forward battery for either the windlass or thruster. It means an extra battery to maintain as well as weight where it is not wanted. The wiring for charging at 3% voltage drop will be as large either way. I would run wires from the house bank forward for both items, assuming the alternator feeds the house bank. Less expensive, less maintenance.

I agree with the above though - if you do this it should be a separate bank.

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post #4 of 19 Old 11-20-2013
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Re: Bow thruster - dedicated battery bank cabe

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I wouldn't install a forward battery for either the windlass or thruster. It means an extra battery to maintain as well as weight where it is not wanted. The wiring for charging at 3% voltage drop will be as large either way. I would run wires from the house bank forward for both items, assuming the alternator feeds the house bank. Less expensive, less maintenance.

I agree with the above though - if you do this it should be a separate bank.
This type of heavy load typically requires a 1% line loss! which would require 0gage or bigger for a 30' run (there and back). If you go much further than 30' you have to go up to 000 gague wire. Frankly to not have a dedicated battery bank to run a bow thruster is a little nuts, at least until you start running 24v systems. The line loss is just to high, and you wind up having to use massive cables to carry the load.

Btw 3/0 runs about $6/foot on a 50' reel, so minimizing run distance can also save a lot of money.

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post #5 of 19 Old 11-20-2013
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Re: Bow thruster - dedicated battery bank cabe

as an option, I installed a dedicated deep cycle battery for the windlass. Then connected an echo charger to the house batteries to keep the windlass battery charged.

If you do the math, the actual amp-hour rqmts of the windlass battery aren't that huge. The amperage draw is, but not the time requirement. Our Maxwell 1500 can draw up to 125 amps. But it only takes about 10 mins max running (overly generous) to raise the anchor. So worst case, it's only consuming about 20 amp hours.

The echo charger pulls up to 15 amps off the house whenever it sees over 13 volts. So worst case, the windlass battery is topped off in just over an hour of engine run time.

With only a 15 amp load, the wiring can be much smaller (and easier to run, and cheaper). Yes it does add a battery to the PM list. And it adds some extra weight. But for us it was a reasonable trade-off.

It also gave me an easy spot to tap for power for the salt water wash down pump.

Don't have a bow-thruster so can't comment on those loads or how that might change the calcs

YMMV
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post #6 of 19 Old 11-20-2013
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Re: Bow thruster - dedicated battery bank cabe

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This type of heavy load typically requires a 1% line loss! which would require 0gage or bigger for a 30' run (there and back). If you go much further than 30' you have to go up to 000 gague wire. Frankly to not have a dedicated battery bank to run a bow thruster is a little nuts, at least until you start running 24v systems. The line loss is just to high, and you wind up having to use massive cables to carry the load.

Btw 3/0 runs about $6/foot on a 50' reel, so minimizing run distance can also save a lot of money.
Yes, I agree the wire should be large - I would use 3/0 or 4/0. But remember the wires connecting the house bank to the forward battery would have to be large as well otherwise the forward battery will seldom if ever be fully charged. Even with a 3% voltage drop 14.4 in bulk charge becomes less than 14 volts. So to do it properly the wire costs would be about the same. I have not used wire smaller than 2/0 on a windlass by itself.



I have installed several windlasses or thrusters, both in some cases, and it works well. The engine is usually running when either is in use, which does give you a higher voltage to start with.

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post #7 of 19 Old 11-20-2013
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Re: Bow thruster - dedicated battery bank cabe

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as an option, I installed a dedicated deep cycle battery for the windlass. Then connected an echo charger to the house batteries to keep the windlass battery charged.

If you do the math, the actual amp-hour rqmts of the windlass battery aren't that huge. The amperage draw is, but not the time requirement. Our Maxwell 1500 can draw up to 125 amps. But it only takes about 10 mins max running (overly generous) to raise the anchor. So worst case, it's only consuming about 20 amp hours.

The echo charger pulls up to 15 amps off the house whenever it sees over 13 volts. So worst case, the windlass battery is topped off in just over an hour of engine run time.

With only a 15 amp load, the wiring can be much smaller (and easier to run, and cheaper). Yes it does add a battery to the PM list. And it adds some extra weight. But for us it was a reasonable trade-off.

It also gave me an easy spot to tap for power for the salt water wash down pump.

Don't have a bow-thruster so can't comment on those loads or how that might change the calcs

YMMV
That works - until you have to re-anchor 3 times to get the anchor to set. With the engine running and large cabling to the windlass there would be no problem. The Echo with its 15 amp max output would not have a hope of keeping up.

A thruster would work better with an Echo Charge as you describe. Even with it's high current draw, it is only used for a few seconds at a time. With a windlass I would use an ACR and heavy (2/0) cabling as its use may in certain conditions be required for a much longer period of time.

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post #8 of 19 Old 11-20-2013
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Re: Bow thruster - dedicated battery bank cabe

Mitiempo, help me understand a little more.

Even a low end deep cycle battery is rated for over 100 amp hours. Assuming only drawing it down to 50% yields 50 available amp-hrs. Even with only minimal charging during the anchoring evolution and with the max possible draw on the windlass (not sure what you'd to be lifting to get that draw) it should be possible to get through at least 3 evolutions and still not tap into the reserve capacity of the battery.

Or am I missing something on the math here?

And, of course, we don't want to open up the dreaded anchor topic with what anchor to choose to get a set on the first attempt.
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post #9 of 19 Old 11-20-2013
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Re: Bow thruster - dedicated battery bank cabe

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Originally Posted by paperbird View Post
Mitiempo, help me understand a little more.

Even a low end deep cycle battery is rated for over 100 amp hours. Assuming only drawing it down to 50% yields 50 available amp-hrs. Even with only minimal charging during the anchoring evolution and with the max possible draw on the windlass (not sure what you'd to be lifting to get that draw) it should be possible to get through at least 3 evolutions and still not tap into the reserve capacity of the battery.

Or am I missing something on the math here?

And, of course, we don't want to open up the dreaded anchor topic with what anchor to choose to get a set on the first attempt.
A 100Ah battery is rated at a 5A load..... If you apply a 5A load for 20 hours by the time the bank hits 10.5 V you will have 100 Ah's.....

Run 125A loads and your 100Ah battery becomes a 38Ah bank when corrected for Peukert.... Course your windlass will not always draw 125A, and at each start up can spike to 250+ amps, but the bank still is not being used at any sort of loads that would lead to it producing anywhere near 100Ah's...


When I have time later I will post some thoughts for consideration regarding bow banks etc...
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Last edited by Maine Sail; 11-20-2013 at 05:46 PM.
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post #10 of 19 Old 11-20-2013
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Re: Bow thruster - dedicated battery bank cabe

Hmm - maybe this weekend I'll pull out the clamp-on ammeter and see what the windlass actually draws when hoisting the chain/anchor. It would be interesting to see the actual curve of how much the thing draws under various conditions.
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