On board power solution

[[2574]]

I'm starting to think through a power plan for the boat and would appreciate a general discussion as to what others do.

I've a yacht with a 50hp yanmar and 50A alternator with Adverc battery management. I'd like to have a robust power solution that enables us to minimise the length of charging time but enough power on board so as not to be constantly utterly neurotic about power consumption.

The big question I'm struggling with is whether to fit a 240v generator (for battery charging and occasional 240v consumption) or whether to fit an uprated alternator (or maybe a 2nd alternator) with a 1/2kw inverter. This latter idea seems to me to have the merit of not carrying another engine in the boat, it consumes less space and is cheaper. It does however mean running the main engine to charge batteries. I think I need additional battery capacity (600ah?) for both solutions. I reckon our average consumption might be around 5 or 6 Amps so at 50% of capacity 600ah would give us about 50 or 60 hours between charge requirements. We're not after air con and only plan to run a cool box, not a freezer.

I appreciate that a wind generator might be part of the solution but at this stage I'm trying to make the 240v diesel generator yes/no decision. Does anyone have any views/experience that they might share?

Thanks in advance of replies.

Rob

 

[fireball]

The worst thing I find is generators that run all night ... usually on one of these "big ships" - you know, the ones that take 20 volunteers out for a "day sail" ...

50-60hrs between charge requirements is quite a time for running a cool box, so sounds like you're gonna liveaboard or be "on holiday" for quite a bit ... then I would imagine your consumption would go up as a cool box alone draws 5Ahs (thats what ours apparently pulls!).

I cannot see any difference really between running a generator or the main engine, except for the "occaisional 240v use" I'd've thought an uprated alternator, perhaps with a battery management system would be a far better investment at this stage.
Couple that with the advice on wind and solar power that you'll get shortly and you should get a decent system....

If you're not running anything significant on 240v (500w is not _that_ significant - what is the "device"? if you don't mind me asking!?) then IMO there is insufficient need for the 240v generator.
If you were wanting to run loads of 240v equipment - Microwave, Dishwasher, Washing machine etc etc (how you get all this stuff on a small boat is beyond me!) then there could well be a strong requirement though...

 

[Piddy]

Having a huge battery capacity is great until you have to charge them! Sounds obvious, but it all depends on your type of usage: Are you travelling evry day, in which case a bigger alternator is fine: or are you in a marina every other day in which you can suck up all the power you want.
If like me, you don't want to be marina bound or having to motor every day, it comes down to having higher charge rates (i.e. running the engine for less time) or using less power. Wind generators work OK in stronger winds but can be horribly noisy to the level where SWMBO wouldn't entertain one at ant cost after a dreadful nights sleep near one.
I currently run a 70A alternator with a Sterling regulator but am considering re-engineering to try and get 150 or more as I have 700AH of battery caoacity in all to keep charged.
It does give us 6-7 days between charges but takes ages to fully recharge.

No mains units (other than the laptop - which draws about 0.5A once charged) just a hungry fridge!

Cheers

 

[Piddy]

Sorry - replied to wrong poster!

Andy

 

[fireball]

'Sok /forums/images/graemlins/smile.gif

Erm - re Noisy wind generators .. aren't some of them braked so you don't have to have it spinning the whole time?

 

[Guest]

Is this for weekends or extended cruising? Is the issue of multiple independent power sources in the event of engine failure an issue?

You are planning 50 hours between charges which is unusual. A lot of cruisers seem to run engines twice per day especially if the freezer works directly off the engine.

In the end we went for a stand alone diesel generator for redundancy. It was actually cheaper than rebuilding the engine box to allow for a bigger alternator. Then later we converted to solar 'cos we hated the noise of any engines.

Also note that to top up a battery fully requires a lot longer time than just getting up to 80% full mark. But if they are not charged fully then the useful capacity is lower. This is a problem on bigger boat when the generator (normally already oversized) for the last hour is hardly being loaded. This leads to problems and in some of the super yachts they have automatic sensors to switch in water cooled loads just to give the generator something to do.

Also, if cruising, add up your engine hours assuming a normal charge to 95% and work out how many days per oil change on the main engine.

If you do go for a generator make sure it is the correct size and has a proper voltage regulator. If it uses a capacitor then you will probably have to get a larger model than your requirements. It seems that some switch mode chargers have issues with the capacitive 240v generators.

I hope this helps.

 

[cliff]

I also looked at the problem and plumped for bigger alternator and a Sterling controller with a 1.8kw invertor (1.8kw Cont. 3.6kw peak) to meet onboard power demands.
550Ah battery bank plus 85Ah engine start.
I decided on one larger alternator (130A) rather than two smaller ones with the original alternator in the spares box just in case the main one went tits up.

I looked at the cost ov the various options against advantages/drawbacks and could not justify the additional cost of a decent wind gen. (~£900+ cost of mounting hardware buys a lot of "red")
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