Charging a battery in the bow? Lots of questions. Any thoughts?

I had a similar problem a couple of years ago when I fitted a bow thruster with its own batteries in the bow.
An additional problem I faced was that the bow thruster was 24v but the boat system was 12v.
Following much head scratching, the option I went for was an Adverc Oscar battery to battery charger.
The one I needed was a 12 to 24v unit but they do a 12 to 12v.
The benefit of this unit was simplicity of fitting with no heavy cables to route (it was also cheaper than the cost of heavy cable) and the fact that the bow thruster batteries are being charged whenever the donor battery is (either by the alternator or by a shore power charger).
2 yrs on and no problems or lack of charge.
 
Our anchor battery is in the bows, your only issue is the different battery types. You need:

- a smart regulator that handles three battery banks and different battery types (you tell it which battery bank is which type)
- slightly oversized cable from the smart regulator to the anchor battery for charging.

Stick with the 60 amp alternator for the moment i.e. until you see whether it will cope. Ours is 55 amp charging three bigger batteries.
 
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- a smart regulator that handles three battery banks and different battery types (you tell it which battery bank is which type)

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what make and model of smart regulator are you using that handles 3 battery banks?
 
no one seems concerned abt weight in the bow. say 50 metres of chain, an anchor or two, windlass, 330CCA battery... you sure about thst?
 
The echo charge unit is the way to go. I have one for my windlass battery and one for my generator battery. Both AGM type batteries. No maintenace, and self regulating. Dont need to switch it on or off.

Its cheaper than running large sized cables all over the place.

Colin
 
If you are thinking of connecting your bow battery to your rear "house" battery you need to look at the wiring from the bow battery to the thruster / windlass separately from the wiring between the two batteries.

The reason you need heavy wires is to minimize the power loss so that the thruster etc work effectively.

I don't believe you need to provide for the full current flowing from the house battery. The current will be limited by the combination of two effects - the difference in voltage between the two batteries and the resistance of the intervening cable. It is unlikely that the voltage at the bow battery will fall anywhere near zero and, as long as you don't expect the house battery to drive the thruster, you should only care about the resistance in the cable if it is likely to raise the temperature of the cable to a dangerous level (again very unlikely). As someone else said you definitely should have circuit breakers at both ends of the battery - to - battery cable, and they will be sized to prevent the cable going on fire.

I suggest that you size the battery - to - battery cable so that you get the full benefit of the bow battery for your house loads (i.e. for current flowing from bow to stern) , and for convenience of charging the bow battery without unacceptable power loss. But the charging current is unlikely to exceed, say, 30 to 40 amps.
 
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no one seems concerned abt weight in the bow. say 50 metres of chain, an anchor or two, windlass, 330CCA battery... you sure about thst?

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Not concerned at all. God help us if 2 x 14 stone lumps were to nip up to the forecabin for a kip?

When I sailed a dinghy, I recall having to get our weight forward when beating to keep the bow down in the water. I cant remember why, but it seemed to work.
 
I reckon you would be better off with heavy cable rather than another battery. You should be able to share the cable ie one power and one negative to both thruster and winch. Assuming you wouldn't use both at once.

If you have the engine running and you draw huge asmounts of current from the engine battery the alternator will contribute. You do niot need a circuit breaker or fuse in the alternator supply. The alternator will simply reduce in output voltage as the rated amps are drawn so that the alternator will simply supply whgat it can and the restt will come from the battery. The total vltage hence current will reduce accordingly.

Which brings us to the next point that if you had an additional battery then you could not use a VSR because under load the alternator charge voltage would fall so disconnecting the VSR.

The option is to have hard wired bow battery in parallel with the engine battery. This would mean that the engine would use the bow battery to some extent as a start battery so you would need a switch to disconnect bow battery at least occasionally to ensure engine battery is still good.

I I reckon that while various other methods of charging are OK they would never give that useful boost from the alternator while actually in use. good luck olewill
 
Kellyseye is as close to good as you need.

We ran charter boats where the anchor was up and down all day.
The cables to the Anchor windlass -bow thruster need not be bigger than your main battery bank/ alternator cables as that is the biggest current they will receive, the battery should receive full charge during motoring manoevering (60 ft cat had in line 100amp switch breaker to the windlass).
It is unlikely that you you ever have to raise or lower the anchor without the engine running, therefor charging your forward battery.
But bare in mind the 1st law of sailing "If it can go wrong it will" so having a windlass that has manual override of some sort is a life saving feature(a clutch or adjustible break) so that you can raise or lower without power from the batterys.
 
Thanks everyone for the answers. Trouble is there are so many options and opinions I am no nearer a final answer. At least I can dismiss option 2 and 3 which I kinda guessed were not viable.

So a dedicated bow battery charged from the start or domestic batteries, with some wires going forward of undecided thickness, maybe protected at one or both ends possibly using some kind of dc to dc charger. Or.....just run some thick wires forward and upgrade current battery. /forums/images/graemlins/confused.gif

Thanks for input and I am still open to more suggestions.
 
I too have been pondering this problem for quite awhile. I was nearly convinced that running the heavy cables was the only way to go but after reading this thread I found another solution from RUFUS99 that seems to be the answer: a DC to DC charger for the bow battery.

I'm not sure what the difference there is between the DC to DC Charger and the Echo Charger. The ECHO charger was actually my first choice. I have one already for my starting battery but I sent I query to Xantrex about using a second one for the bow battery, they replied that is was not recommended but it seems people are using it so I'm not sure.

Anyway I didn't fancy running the heavy cables so a third battery at the bow and a DC to DC charger seems best to me.
 
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Anyway I didn't fancy running the heavy cables so a third battery at the bow and a DC to DC charger seems best to me.

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I am in a similar quandary except that I already have a battery in the bow.

As far as I can see, my windlass is run fom the domestic batteries in the aft cabin via thick cables. The 200Ah bow battery runs the bowthruster and inverter.

There are two supplies from the alternator itself, (B+1 & B+2), one of which feeds the domestic batteries, and one feeds the solenoid then starter battery. I havent quite worked out how the bow battery is charged, but it doesnt do very well.

With lots of time to think about it, my current thoughts are that whatever I do for charging the domestic battery bank, (Balmar, Sterling, Adverc, whatever), the Sterling battery to Battery charger, from the starter battery, seems to make sense for the bow battery.... not cheap when you add it to what I might spend on the rest of the system but, hopefully, you only do these things once.

(Having said that, I've got a list of things you only do once, and its coming in at about £6K!!!)

Cheers

Richard
 
Hi

I had the identical problem on a 40 footer.

I have a thruster and anchor winch run off a battery in the forepeak. This was initially charged from a mains charger, powered by shorepower or a 4KVA genset. However as I live out on a mooring, I have no shorepower, and I would not want to run the gen set juswt to charge the bow batteries.

So the solution was to install one of Stirling's 32 a/h (I think) battery to battery chargers. This is located next to the engine battery, and detects when the battery is above 13.5V when it starts taking current - so totally automatic.

The connection to the bows is 25mm cable which is the correct size for carrying that capacity (according to Stirling). System works a treat - simple to install, apart from running the cables. Do look for the easy bend cable as sold by people like Furneaux Riddle in Portsmouth.

No regrets on this installation.

However - do you really need a bow thruster? I never use mine, even in a marina. Only really of use when you have lost way and thus steerage, when the first rule of manouvering is not to loose way!

Chris
 
Let summarize the situation :
- you have an electric windlass, which is (maybe) unadequately fed from the engine starter battery through long wires (some 16 m. total)
- you want to install a new bow thruster.
- you are rightly (IMHO) considering installing a new battery in the bow, to take care of both, the windlass and the bowthruster.
- you are worried about the charging of the new battery.

In my opinion, you already have all the necessary ingredients for a successfull installation.

Place the new battery somewhere near its dedicated consumers (windlass and bowthruster).
As a positive consequence, you'll get two relatively "big" cables to take care of the charging current for the new battery (the present windlass cables).

Done!

No new cables, except if you want to remote control either one or both.

Remark : both the windlass and the bowthruster are "special" consumers, as far as they need high current for short time (like the engine starter) thus, the battery can be of low capacity (let say 50 - 80 Ah)
Neither the windlass, nor the bowthruster are likely to drain many Ah. (e.g.: windlass working 3 minutes at 100 A. = 5 Ah. or 10% of the capacity of a 50 Ah. battery!) that means that the "bow battery" will never be deeply discharged, thus never will need heavy charging current, minimizing the voltage drop in the large and "big" charging wires. ... and it is likely that after each draining of the bow battery, either the engine, or the charger will take care of the charging back to 80 - 90% of the capacity.

I have a similar installation on my own boat, and the "bow battery" is now 6 years old, and still going strong.
I use the same battery to power my dinghy's elctric outboard as well, and this discharges it heavily!

No problem so far.

To be as comprehensive as possible : I charged my 3 batteries (engine start - 75 Ah. lead-acid, domestic - 150 Ah. lead - acid, and bow/dinghy - 50 Ah. AGM) with the standard Volvo 30 A. alternator, via diodes and Adverc.
I just replaced my engine for a Beta, which has a 60 A. alternator, but forbid me to install the Adverc (loss of garanty) so for the time being, I manage the whole stuff via a 1 - both - 2 switch. I'll go back to diodes - Adverc during the winter and ... to hell with the warranty!
 
A VSR connection from domestic to windlass batt works for me. It disconnects when voltage is pulled down so fat cables don't seem nec. Also VSR's supplied now operate both ways so if you have spare power in the windlass batt it will sometimes flow the other way! And VSR's are cheap!
 
Something like Sterling's battey-to-battery unit would be ideal for this sort of application. Could have been made for the job. You only want a small one as you are not looking for a fast charge (you don't use bowthrusters and windlasses all the time and there is plenty of time to recharge). I would mount the unit by the remote battery but DO CHECK that there is no maximum resistance in the cabling from the supply battery to the Sterling unit, or phone and ask them (wearing a steel helmet).

PBO say that they are going to publish a test report on these in the November issue.
 
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I would mount the unit by the remote battery but DO CHECK that there is no maximum resistance in the cabling from the supply battery to the Sterling unit, or phone and ask them (wearing a steel helmet).

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Sterling advised me to have the charger unit beside the engine battery - good fat cables to the bows battery (25mm). The system is really good and just what new sailor should be installing. Not sure about the diode splitter options with an adverc, as the bows battery will not be monitored for charge, and consequently could be over charged. You still need big cables what ever route you go because of 12v voltage drop. Its a dead simple bit of kit to fit, with lots of loveley flashing lights that Charles likes so much.
 
DOn't think that connecting the bow battery 20 foot away from the engine battery is a runner - too much voltage drop. I understand that paraleled batteries brought into the same bank really should be - of similar age/state, of similar size, and next door to each other. My bet is on the battery to battery charger set up IMHO
 
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