Electrical power generation on a small yacht

[bluedragon]

I’d welcome a few thoughts on this topic. The yacht is 27ft, a good but old diesel with new Dynastart, usual instruments, GPS, cockpit plotter, usual lights, tiller pilot, VHF…no coolboxes, PCs or the like. I have one engine-start battery around 60Ah and one service battery 75Ah. The Dynastart puts out around 12-15A at best.

For day sailing or nights in marinas, my charging capability vs. amp hours used is fine. But this year I’m planning to do some extensive cruising from the Bristol Channel to Scillies to Ireland to N.Wales (at least that’s the plan!). I could be at sea for up to 48 hrs, and even shorter passages may often end at anchor. That means most instruments on most of the time, nav. lights, extended use of the tiller pilot, etc.

I’ve worked out a number of typical energy demand scenarios for different types of passage and come up with between 35 and 65 Ah over a 24 hr period. To replenish this I’d need to run my engine between say 3-6 hrs per day…not something I want to be forced to do. So I need some additional power generation. I’d rather avoid fitting an alternator for a number of reasons, and would probably still have to run the engine for no other reason than charging. I’m therefore thinking of alternatives. These seem to be:

a) Wind generator: attractive but I’d probably need at least 1.5-2.0A output on average with a typical summer wind speeds to help make up my shortfall. I already have a small Forgen 500, which is fine for keeping full batteries topped-up, but useless for the above purpose. The bigger Rutland and Aerogen types will make my boat (27ft) look like a helicopter flying sideways!!..won’t they??

b) Solar panels: nice idea, but off the coasts of the western U.K. are these a realistic proposition??

c) Petrol generator: perhaps, but noise / size / storage / cost for the good ones?? Is this a viable option in the circumstances?

d) Just take extra topped-up service batteries and recharge all using marina shore power when available. Simple and attractive idea, but it does mean visits to marinas every few days or so.

So…sorry for the long post…but I would like some comments from members who have faced and solved a similar dilemma. Many thanks.

 

[Colvic Watson]

A Rutland 913 won't be too big for a 27 footer and will give most of the amps you need on an average day. Nice bit of kit that works well. More amps for your £ than solar and we get lots of wind in the UK! Just a note about solar, all modern panels like bright days rather than sunny days, so don't worry about the weather having to be hot (in fact they work best when not hot).

 

[LORDNELSON]

I have puzzled over this for some time. My solution has evolved as follows: 1. A 15 watt solar panel used in port when the boat is idle (ie no one on board) this keeps the starter battery at a reasonable level of charge. 2. A 300 watt portable four stroke genny for use when remote from other yachts but occupied, fed into 230v ring main to keep battery charger going, this ensures I can run my eberspatcher and frig and have one or two 230v table lights on. 3. Engine alternator outputs, in my case, 70 amps, and its charging is operated through an Adverc control system. The above seems to keep the battery charge levels well up on our type of sailing whether we are on extended cruises or weekends, however, we do little night sailing. Of course if we are in a marina we connect to shore power and the smart battery charger is kept on. Our battery situation is 2 x 110 ah for domestic and 1 similar sized starter battery. I do feel that you may well need to consider having two domestic batteries. You do have a problem with the dynastart's relatively low output. It would be interesting to know why you are avoiding an alternator - to my mind it is the heart of the system.

 

[oldsaltoz]

G'day bluedragon,

You have a power plant <a good but old diesel with new Dynastart> I would be looking at installing an alternator, reliable and not too expensive, no noise, no messing with fuel as in filling a gen set.

Wind generators can be a hazard, and try sleeping with one, no thanks, and not cheap.

Solar panels should do the trick, we run 2 x 80 watt and 2 x 120 watt units, have 6 house batteries and 2 start batteries [one for each engine]. We also have 2 small fridge/freezers on 24 hours a day 7 days a week, no problems. We do get a good deal more sunlight though, but I'm pretty sure you can have enough panels for almost any climate.

Petrol generator: We used to run a portable gen set when on extended fishing trips. I removed the thermostats from both freezers so they ran flat out, also installed a couple of computer fans to speed things up. But the noise was so bad we used to fill the tank on the genie then go off in the tender for an hour or so fishing to get away from it. You don't have a purchase an expensive unit, just pick up a cheap one and sell it on when you have done with it, low hours and still looking new should bring a reasonable price.

Extra topped-up service batteries and recharge using marina shore power, not sure about this, storage problems, and as you say it means you have to find a power outlet, and that may mean marina fees every few days.

There is another method you might like to look into, the towed version of an alternator, I'm not all sure what sort of output they provide, but it has look better than a helicopter flying sideways, less noise than a gen set, less weight than extra batteries too.

Let us know how the trip goes and what you used to keep your systems charged.

Andavagoodweekend......

 

[michael_w]

Is it possible to modify the engine to have an alternator and a starter motor? My old boat was built with a Volvo MD5A (dynastart) was changed at some time to a MD5B (alternator). All I did was fit an Adverc and a shunt ammeter to keep an eye on things.

Incidentally the Adverc and the ammeter will be a "must fit" on any boat of mine.

FWIW I've found solar panels to be very useful. There're nice and quiet too /forums/images/graemlins/cool.gif

 

[gfbalduc]

My favourite subject, I cannot resist!! /forums/images/graemlins/wink.gif

You seem to have your numbers clear enough; just a few remarks:

- service battery: considering that you should cycle your battery between, say, 80% and 50% of its full-load, this means you should draw not more than 25-30 Amp-hours out of your 75Ah battery. This means your battery will last less than half a day without recharging.
I would think that you should at least double your service battery capacity, to begin with.

- wind generator: I have an Aero6gen and yes, it looks like you have a helicopter on your transom, and all this to get an average of 30Ah in 24 hours, with normal wind conditions.

- solar panels: count on 30Ah per day per square meter. If that sound disappointing, well it is!

- petrol generator: noisy, smelly, difficult to use when under sail unless you do a fixed installation, potentially dangerous due to additional petrol to be carried.
I have one on board as a last-ditch resource, and have used it once in 30 years!
For me, on a small boat, it's much better to use the inboard engine, if you have to.

If you already have a small wind generator, probably your best approach would be:
- get a larger service battery
- keep your windgen or consider a somewhat bigger one
- add the largest solar panel you can live with
- use engine to complement whatever consumption windgen+solar panels have failed to compensate

You should also ask yourself how often do you expect to have to motor due to lack of wind or just to go in/out of anchorages?
FWIW, my personal experience is that with an arrangement like the one above, I almost never need to run the engine just for charging, and when I do I normally have to run it for not more than one hour at a time.

 

[Birdseye]

I've tried the lot and only the engine alternator is really up to the job with a 60 amp output. Solar panels are OK for trickle charging on a mooring, but you would need to get some decent sized chrystalline panels to start to even match your dynastart at noon on a bright summer day. Let alone in the morning or evening. I have an amorphous silicon panel rated at 30w (from memory) and despite being reportedly a very good panel it struggles to keep up with natural battery discharge over a long period let alone re-charge anything much.

Wind generators come closest but even these have limited output, require a reasonable breeze to work decently, make noise and vibes to varying degrees. My admittedly short experience of one was that I would rather have the engine running for an hour than the alternative of the wind gen for 24 hrs. And size is everything in wind generators - the basic physics means that you have to have bigger vanes to get more power.

Finally, do you really want a portable generator and associated petrol on your 27 footer. Seems a bit silly somehow to have two engines to keep your batteries charged when you could do with one.

When longer term cruising myself I found that the engine was used for a significant proportion of the time simply to make port, leave port make dead upwind when the winds is (as usual) blowing directly from your destination, and deal with very light winds. Maybe as much as 50% of the time under weigh had the engine running. Now I too dont like the engine and would never have dreamed that it would be that much, but it was. So you might find that you are addressing a problem that you dont have.

And I would add another battery if I could.

 

[Mudhook]

Throw away the Dynastart and fit a decent alternator of around 70A output, plus an Adverc or Sterling charging system. Beef up your batteries to at least 1 x 110Ah plus the starter battery. Don't waste any money on solar or wind power. And use a paraffin anchor light. I have similar electrical usage to what you plan on a similar boat and I have never been compromised on electrical power.

Regards, Mudhook

 

[thalassa]

Dynastart NO . Alternator_YESSSSS /forums/images/graemlins/smirk.gif

 

[wizard]

I agree -alternator and a Merlin alternator booster cuts the charge time by about a third I think, certainly made a difference to my charging times.
I also have a small suitcase Kipor 2KW generator with a pure sine wave output that can charge the batteries when extended anchoring and can also run the laptop
it was only £245 on Ebay.

 

[Dave99]

You can get a combined water/wind generator. Cant remember the name Aquagen or something. Anyway I know people who used instruments, fridge and radar and when using it as a towed generator it coped with those demands without any loss. A bit of a hassle if you are in coastal waters, best suited to long passages

 

[bluedragon]

There's some really good information coming back from all of you...please keep it coming! Let me just expand on why fitting an alternator has not been my first choice a) I need the Dynastart to start the engine, so an alternator has to be an "add-on" b) mounting an alternator and its drive belt is not easy with the space / engine / compartment configuration available c) I already have barely enough HP (6-8) for motoring into head seas - an alternator will suck even more out of the engine I fear. It is possible to do...I'd just rather not do it if a viable alternative exists...in the end I might have to bite the bullet and fit one...I know that.

 

[William_H]

As already suggested solar and wind power are not the way to go. Especially for one trip.
So firstly minimise current drain ie you don't really need instruments although Autopilot is worth using.
An alternator is worth fitting. I suggest you consider using it just for your service battery. If you balk at the cost of a smart regulator you might like to try a manual control of alternator current. You will need an ampmeter. Then in place of the regulator you fit a variable resistor of about 20 ohms wire wound of 10 watts rating. You simply start the enginne and using the resistor increase the field current to the alternator which should increase the alternator voltage and hence current into the battery. If you can force 30 amps or more into your battery for an hour you will have recovered much of your usage. After that period you need to reconnect the regulator using switching so that the battery is not fried when using the engine for longer periods. The downside of this system is that it is not automatic and so if you forget to turn off you can do some harm to the batteries. The good thing is that you can squeeze every amp into the batteries for the engine running time. Note you should not have the batteries connected to any other services when charging as the voltage may rise a little higher than normal. Do a search on google for alternative power sources where they use this kind of alternator control for car alternators driven by wind or water.
No I don't think it is practical to do this to your dynastart as it may not stand up to the abuse like an alternator can. (Burnt commutator brushes etc.) All the same the first thing you need is an ampmeter to find out what it really can do.
To reiterate use your boat engine to provide electric power. You will not notice the loss of engine power and if you do, fit a switch to disconnect alternator at full poower setting. (or manually) good luck olewill

 

[David2452]

Methanol fuel cell charger, an almost silent 100ah per day regardless of sun or wind?

David

 

[trouville]

I understand in the North solar panels dont give there maximum! Ive found that a 25w always on and 85w regulated or keep a close eye on the charge.

You will need batteries to store the charge i have 2 dryfit gel deep cycles and 95ampp Varta marine battery(would have more but room and weight!!)

That seems to do fine though i havent fitted a fridge yet so i only put the 85w on to see where it could live!! At the moment thats where the side dodge is.

I also have a small petrol generator that ive used less than once a year!! But once it was very useful. I put it aboard recently to run my SSB If you buy a Honda i think the smallest is 600w? They are very small light? and very quite!!

If you dont have a fridge 2X25w should be more than enough if not buy a third!! The 20/25w panels are very handy for a smaller boat as you can move them about.

 

[bluedragon]

Thanks William. In fact I've seen this setup on a similar boat...alternator manually controlled by a rheostat. I was thinking last night whether I could have one mounted in such a way that it was only brought into play when I needed it...and it needn't be a large one as the Dynstart will output up to 15A. Needs some clever engineering to mount and drive...must think about this.

Those who have suggested solar panels...the most attractive idea would be to have a freely moveable panel with fly leads that I can mount at the best angle to the sun as needed. As I'll usually be on board (at anchor, etc) this might well be an good idea anyway. Any thoughts anyone on the best size / type / value for money makes?? 1or 2x25W has been suggested as a starting point.

 

[bluedragon]

[ QUOTE ]
Methanol fuel cell charger, an almost silent 100ah per day regardless of sun or wind?

[/ QUOTE ]

Great idea...I had some involvement in fuel cell technology in an earlier life...and in the future this may be the way to go. But right now won't these cost £'000s?

 

[bluedragon]

[ QUOTE ]
A Rutland 913 won't be too big for a 27 footer and will give most of the amps you need on an average day. Nice bit of kit that works well. More amps for your £ than solar and we get lots of wind in the UK! Just a note about solar, all modern panels like bright days rather than sunny days, so don't worry about the weather having to be hot (in fact they work best when not hot).

[/ QUOTE ]
I'm going to have a look at one of these. There's a few on boats at the Y.C. I think...time for a walk down the pontoons anyway. Thanks.

 

[Colvic Watson]

Re some of the comments about wind generators being noisy: this is normally due to the bearings. They do wear out and are damaged if the machine is left stopped for long periods as the head rocks back and forth slightly on one side of the bearings - £15 for the pair and it makes the machine virtually silent again. Sometimes the noise and vibration is due to poor fitting of the pole.

It is expensive to by a set up, close to £700 for the head unit, SS pole and regulator, but once there it needs no fuel, works almost every day and if there's no wind you are probably having to motor and so charging that way.

Perhaps the best way of helping your situation is a very low tech one. We realized last year that we were just using too much power. We bought 4 good quality oil lamps and used them instead of 12v lighting when not in a marina. We do have an electric cool box but only use it when the engine is running. It's not a solution the big boat boys will like, but the cost and enormous weight of extra batteries plus the hassle of trying to bung in more and more amps just wasn't worth it for us.

 

[poter]

Just a quickie...to follow on from this, what is the best instrument to show the battery charge & condition?

poter