Thoughts on Bow Thrusters

grahamdouglass · Nov 21, 2021

I'm thinking of running my windless from my bow thruster batteries. What follows is a brief description of my bow thruster, windless, and DC panel wiring. Followed by questions on charging considerations.

A couple of years ago I had a Lewmar bow thruster added to my boat. It is powered by two 12 V batteries, wired to provide 12 volts. The charge is maintained by a #8 wire, protected by a 30 amp fuse that goes from the batteries to a positive distribution post in my electrical closet. This distribution post it fed from my main distribution (house battery xantrex charging) located in my engine room.

At present my Tigress windless is fed by a 40 year old #1/0 cable, of unknown Taiwanese quality that goes from my main distribution in my engine room through a 100 amp fuse and a 30 foot run to the windless.

My proposal is to run my Tigress windless from my bow thruster batteries with some 2/0 welding cable that I have on hand. No run would be more than 4 feet.

I also just completed a new DC panel install (Blueseas 8380), on the other side of my electrical closet, that has a multiple bank voltage metering capability so I will be able to see what the voltage is on my bow thruster/windless batteries. The sensing wire for voltage measurement is independent from the panel.
The panel is fed by a 2/0 distribution wire from engine room that steps down to an 18" long 2 awg wire after the shunt to accommodate the panel swinging out on a piano hinge.

Question
Do I leave my #8 wire to my positive bus bar in my electrical closet as my charging wire as is or do I employ a Xantrex echo charger from my main distribution bar in the engine room. Could I run the echo charger from my 2/0 main feed in the electrical closet before the shunt? Do I need an echo charger at all?

I also have an isolator in the engine room for my house bank and start battery fed by my alternator (150amp). Considering the size and expense to run a cable from my isolator to my thruster batteries (30ft), is there any sense to do that? I could use my old 1/0 wire that is all ready in place.

I hope I explained myself coherently.

rgano · Nov 21, 2021

Use of welding cable in boats instead of properly sized electrical cable with the concomitantly larger strands is often frowned upon, but otherwise I certainly agree with powering the windlass from a local battery. I believe I would muster up a dedicated 120 volt charger and post it well forward. Rather than rip out the old but apparently functional 1/0 cable, why not use it to connect the bow batteries to an echo charger or ACR located at the engine room battery bank to get underway charging from the alternator when the genny is not running?

Bacchus · Nov 21, 2021

Agree with Rich re using proper size tinned marine cable vs welding cable. Why cut corners to save $ when an important system aboard?
Use best practices and quality supplies and sleep soundly.

O C Diver · Nov 21, 2021

Couple of points to consider:

While thruster requires more amperage to run, your windlass can draw far more amp hours out of the batteries depending on water depth. Make sure the bow thruster batteries are deep cycle and up to the draw down.

If you're dramatically increasing the draw down of your batteries, I would recommend recharging with a 20 amp battery charger. My preference would be a 120 VAC running off an inverter, generator, or shore power.

Ted

sean9c · Nov 21, 2021

Shouldn't the thruster battery be a start battery due to the high amp draw?

O C Diver said:
Couple of points to consider:

While thruster requires more amperage to run, your windlass can draw far more amp hours out of the batteries depending on water depth. Make sure the bow thruster batteries are deep cycle and up to the draw down.

If you're dramatically increasing the draw down of your batteries, I would recommend recharging with a 20 amp battery charger. My preference would be a 120 VAC running off an inverter, generator, or shore power.

Ted

Bacchus · Nov 21, 2021

O C Diver said:
Couple of points to consider:

While thruster requires more amperage to run, your windlass can draw far more amp hours out of the batteries depending on water depth. Make sure the bow thruster batteries are deep cycle and up to the draw down.

If you're dramatically increasing the draw down of your batteries, I would recommend recharging with a 20 amp battery charger. My preference would be a 120 VAC running off an inverter, generator, or shore power.

Ted

sean9c said:
Shouldn't the thruster battery be a start battery due to the high amp draw?

If you use AGM they do both deep cycle and hi amp (start) fairly well and why many spec both AH and CCA. They are also well suited for placement close to hi amp draws where FLA are impossible or difficult.

O C Diver · Nov 21, 2021

sean9c said:
Shouldn't the thruster battery be a start battery due to the high amp draw?

That's what mine are. Depending on amperage draw of the bow thruster and the type of deep cycle battery, you could use deep cycles. I wouldn't have any heartache using a pair of Fireflys in this application. I don't think most sealed lead acid batteries will live a long life in this application.

This is one of those areas where 24 volts makes a big difference.

Ted

GingerMd · Nov 21, 2021

Something to consider is that (at least for me) you are always running your engines when operations the windlass or bow thruster. That helps with current supply. I have no batteries in the bow. I do have maybe 2 AWG (I’d have to check if its 0) running from my house bank. I have had no issues. I have measured voltage at the windlass and thruster during operating with only a few tenths of voltage drop. I’d vote for simplicity with heave gauge wire.

Bacchus · Nov 22, 2021

O C Diver said:
I don't think most sealed lead acid batteries will live a long life in this application.

Ted

I have an 8D AGM serving my B & S thrusters. It is still doing very well after 8 seasons. This year I moved my single engine start over to it to make my house bank a pure house vs combo w start. Side benefit was run to starter was about half of previous.
I dont see why this isn't a good application for AGM...

jleonard · Nov 22, 2021

[Something to consider is that (at least for me) you are always running your engines when operations the windlass or bow thruster. /QUOTE]

Not me. I would run my windlass to take up most of the scope 20 or so feet at a time before I fired up the engine. This would give the chain time to clean off.

O C Diver · Nov 22, 2021

Bacchus said:
I have an 8D AGM serving my B & S thrusters. It is still doing very well after 8 seasons. This year I moved my single engine start over to it to make my house bank a pure house vs combo w start. Side benefit was run to starter was about half of previous.
I dont see why this isn't a good application for AGM...

8Ds aren't batteries, they're ballast. A single battery that weighs more than I do, isn't a battery. An 8D is a back injury waiting to be inflicted.

Ted

sean9c · Nov 22, 2021

When the logic side of my brain takes over I think, my engine is running so my alternator is making current, my ACR's have connected all my batteries together and when I'm done using my thruster/windlass my alternator will make up any amps that I use, why do I need a big windlass/thruster battery?

Bacchus · Nov 22, 2021

O C Diver said:
8Ds aren't batteries, they're ballast. A single battery that weighs more than I do, isn't a battery. An 8D is a back injury waiting to be inflicted.

Ted

No argument there. Another 8D will not be brought aboard. My plan is a pair of GP31 AGMs as a replacement. I don't see why an AGM isn't well suited for the application?

O C Diver · Nov 22, 2021

sean9c said:
When the logic side of my brain takes over I think, my engine is running so my alternator is making current, my ACR's have connected all my batteries together and when I'm done using my thruster/windlass my alternator will make up any amps that I use, why do I need a big windlass/thruster battery?

2 reasons:

If using the thruster to dock, the battery won't be recharged before shutting the engine off. Like wise, when anchoring, depending on your technique, the windlass may be used (maybe more than once), and then not recharged before shutting down. Then it's used before recharging to recover the anchor.

Second reason is that most batteries lose charge over time while sitting. A charger maintains the batteries connected to shore power.

Ted

backinblue · Nov 22, 2021

jleonard said:
[Something to consider is that (at least for me) you are always running your engines when operations the windlass or bow thruster. /QUOTE]

Not me. I would run my windlass to take up most of the scope 20 or so feet at a time before I fired up the engine. This would give the chain time to clean off.

Click to expand...

So you are using your windlass to move the boat? I thought that was a no-no. I always start the engine before attempting to raise the anchor. Firstly, I want to be sure I have a running engine before I begin to un-set the anchor, and secondly, small bursts of fwd with the engine, moves the boat forward so the windlass is only lifting the slack rode and anchor but not pulling the boat forward. Normally my wife is at the helm and I am at the bow and simple hand signals work fine.

BDidier · Nov 22, 2021

I just installed a two battery, 6V series AGM bank under the vee berth to run my windlass. It's about a 12 foot run, round trip, of 2/0 cable to power windlass with 500A solenoid switching the big cable. We use a Sterling battery to battery 12V, 30 Amp charger to charge from the Firefly house bank. The Sterling programmable charger allows custom charge profile for the AGM. The charging circuit is about 30 feet of #4 AWG for 1% drop. The windlass bank is being charged/held at float whenever the house bank is being charged by 110VAC shore or generator or 12VDC alternator. Not a lot use yet but all is working as designed. Rod Collins helped me with schematic reviews from the beginning my 12V system design.

Jeff F · Nov 22, 2021

I have the same windlass and it is wired to my thruster bank with its own 100 amp breaker/disconnect. I think that's what you are describing as your future state. No issues or concern, although recent discussion here on shutting things down at the main panel and runaway windlasses got me thinking a bit. My windlass is always powered up.

To keep my thruster bank charged I use a 30 amp dc-dc charger that is powered from my house bank. It sounds like you have wiring in place now that would support that. In my case I used a Victron unit, and configured it to charge based on house bank voltage triggers, so if my house bank is being charged by any source the charger for the thruster bank is on.

jleonard · Nov 23, 2021

backinblue said:
jleonard said:

So you are using your windlass to move the boat? I thought that was a no-no. I always start the engine before attempting to raise the anchor. Firstly, I want to be sure I have a running engine before I begin to un-set the anchor, and secondly, small bursts of fwd with the engine, moves the boat forward so the windlass is only lifting the slack rode and anchor but not pulling the boat forward. Normally my wife is at the helm and I am at the bow and simple hand signals work fine.

Click to expand...

Only when the water is quiet, which it usually is in the morning when we would raise the anchor.

I would take in some slack, then the boat would inch forward by the weight of the chain. Then after a few minutes I would repeat that cycle. It never put much strain on the windlass.

When we got to the last 30 or 40 feet then it was time to fire up the smokey Joe and finish pulling it up.

I never worried about a running engine, it always started quickly.

O C Diver · Nov 23, 2021

Bacchus said:
No argument there. Another 8D will not be brought aboard. My plan is a pair of GP31 AGMs as a replacement. I don't see why an AGM isn't well suited for the application?

An AGM is good. For a thruster battery, I view it's use as identical to an engine battery. Generally short duration pulses of very high amperage. Some AGM batteries are listed for starting, some for deep cycle, and some as dual purpose (great at neither). So an AGM for a thruster battery should be listed as an engine battery, not deep cycle, and a compromise as dual purpose, IMO.

Ted

ofer · Nov 23, 2021

backinblue said:
jleonard said:

So you are using your windlass to move the boat? I thought that was a no-no. I always start the engine before attempting to raise the anchor. Firstly, I want to be sure I have a running engine before I begin to un-set the anchor, and secondly, small bursts of fwd with the engine, moves the boat forward so the windlass is only lifting the slack rode and anchor but not pulling the boat forward. Normally my wife is at the helm and I am at the bow and simple hand signals work fine.

Click to expand...

Agreed!

AlanT · Nov 23, 2021

backinblue said:
jleonard said:

So you are using your windlass to move the boat? I thought that was a no-no. I always start the engine before attempting to raise the anchor. Firstly, I want to be sure I have a running engine before I begin to un-set the anchor, and secondly, small bursts of fwd with the engine, moves the boat forward so the windlass is only lifting the slack rode and anchor but not pulling the boat forward. Normally my wife is at the helm and I am at the bow and simple hand signals work fine.

Click to expand...

+1
Windlass is used to pull up the anchor/chain, not to pull the boat to the anchor. Once the boat (under power) is directly above the anchor a nudge forward with the engine will usually break the anchor free so the only 'work' the windlass has to do is raise the dead weight of anchor/chain.
~A

cardude01 · Nov 25, 2021

Don’t want to hijack the thread but have a (hopefully) pertinent question.

My house bank (4 Lifeline group 31 125AH) also runs my bow thruster, and after 7 years my house bank is getting so weak that when I use my thruster it shuts my electronics off due to low voltage. On a recent trip I started to use the house bank “parallel” switch that connects the house bank to the start battery,which is brand new and in good shape. I’m obviously using this switch in reverse of it’s intended use and just wondered if it was harmful?

Bacchus · Nov 25, 2021

cardude01 said:
Don’t want to hijack the thread but have a (hopefully) pertinent question.

My house bank (4 Lifeline group 31 125AH) also runs my bow thruster, and after 7 years my house bank is getting so weak that when I use my thruster it shuts my electronics off due to low voltage. On a recent trip I started to use the house bank “parallel” switch that connects the house bank to the start battery,which is brand new and in good shape. I’m obviously using this switch in reverse of it’s intended use and just wondered if it was harmful?

I don’t see why that should cause any problems under normal use.
The only problem will be if/ when you forget to separate the banks at anchor and run both house & start low. My eng start was combined with my house bank and what you outlined was one of the main reasons I moved eng start to my thruster bank to leave a pure house bank.

OldDan1943 · Nov 25, 2021

My thoughts: Alway over size your thrusters HP. Some designer use bare minimum and that's not good enough on windy days.
Next if at all possible, go with hydraulic thruster. Run all day pretty much without damage.
If you go with electric, have healthy batteries.

O C Diver · Nov 25, 2021

cardude01 said:
Don’t want to hijack the thread but have a (hopefully) pertinent question.

My house bank (4 Lifeline group 31 125AH) also runs my bow thruster, and after 7 years my house bank is getting so weak that when I use my thruster it shuts my electronics off due to low voltage. On a recent trip I started to use the house bank “parallel” switch that connects the house bank to the start battery,which is brand new and in good shape. I’m obviously using this switch in reverse of it’s intended use and just wondered if it was harmful?

If practical, it might be worth running the bow thruster off the engine battery. Unless you use the thruster with the engine off, you're probably putting a load similar to starting the engine, on the battery. Also, the alternator is offsetting some of the draw. I still prefer the thruster on its own battery located at the thruster.

Ted

cardude01 · Nov 25, 2021

Bacchus said:
I don’t see why that should cause any problems under normal use.
The only problem will be if/ when you forget to separate the banks at anchor and run both house & start low. My eng start was combined with my house bank and what you outlined was one of the main reasons I moved eng start to my thruster bank to leave a pure house bank.

Sorry I wasn’t clear. While using the thruster I pressed the combiner or parallel switch on the engine start panel to give the thruster a little boost.

backinblue · Nov 25, 2021

Just my humble opinion, I think thrusters are better powered from the start bank than the house. That's how mine was wired from the factory. Makes sense to me because:
1) Engine is already running prior to using thrusters
2) Start batteries are fully charged when leaving or returning to dock
3) Thruster loads are short period, high current loads, better suited to a starting battery
4) No risk of voltage drops affecting electronics or anything else on the house bank
5) Engine starting is never a concern. Starts with a click of the key, never even hear it turn over. Load on the start bank for the engine is minimal.

OldDan1943 · Nov 25, 2021

My thruster were on the single 4D start battery. While docking the Cummins kept shutting down on low voltage about 10.6vts. Was a bad battery. I had the bow thrust rewired to the 3X4D house batteries. Now I have both thrusters on the house batteries. Soooo, if I still need more, I can bring the start battery in parallel. Of course the main engine, generator and battery charger are all on line too.

cardude01 · Nov 25, 2021

OldDan1943 said:
My thruster were on the single 4D start battery. While docking the Cummins kept shutting down on low voltage about 10.6vts. Was a bad battery. I had the bow thrust rewired to the 3X4D house batteries. Now I have both thrusters on the house batteries. Soooo, if I still need more, I can bring the start battery in parallel. Of course the main engine, generator and battery charger are all on line too.

That’s exactly what I am doing. Interesting.

Unclematt · Nov 25, 2021

I had a stern thruster (no bow thruster) installed in the spring. He installed two series 32 AGM's with there own charger. I now have a 800 ah AGM house bank, AGM start bank, set of AGM for the stern thruster and separate lead acid series 32 for the generator start.

Thoughts on Bow Thrusters

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