Self sufficient electrics.

[sausage]

I am very likely purchasing a vessel that has no way of generating elctricity apart from the engine.

Im considering wind, solar or even petrol.

In order to calculate my needs in terms of identifying an adeqaute solution, do I just need to understand the following:

What systems will I be running and what amp hours do they use?
Does that mean I read the manuals on all systems, radio, log, windex, gps, fridge, lights etc etc and add them all up?

So, lets say Im using 5 amps per hour, what about the different voltages? Should I work out the mean average, and then use watts = amps * volts to see what sort of wattage I need to put into the system?

Another couple of questions:

1. Is it as simple as generator, regulartor, shunt, battery and monitory?

2. What would I need to do to be able to run something from the plug sockets when Im sailing, and not on shore power? I.e. if I want to charge my laptop or phone from the wind generator?

Sorry if this is a can of worms!

I apprecaite this is potentially quite a technical thread, so Im happy with a simple overview answer and to go away and read the manual if that is what is needed.

Thanks in advance.
Mark

 

[TigaWave]

First thing you need to look at is how are you going to use the boat, how much time will be spent at anchor, sailing, motoring?

On passage one towed generator producing 7-10 Amps @ 13-14Volts was all we needed, when cruising between anchorages tha engine would be used 1-2 hours a day sometimes we'd stream the towed gen if the trip was longer than a couple of hours and a wind gen was up when at anchor which also covered everything.

We didn't have low energy LED bulbs and used a laptop daily as a plotter and weather fax/text system with a printer running of an inverter.

If you use an inverter or adapter dc - dc to charge things just keep an eye on the voltage, if the wind gens running you want the voltage to be around 13.00v if it drops much below that then you're risking draining the batteries.

Always make sure you have one battery isolated as an engine starter and this should be up around 12.75v all the time.

 

[VicS]

You need to estimate as accurately as possible how much "power", in Amp-hours (Ah) every item will consume in 24 hours.

To do this you need first to know the current consumption in amps. If you know the power in watts then divide that by 12 (assuming you have a 12volt system) to get the amps.

Next you need to estimate the total time, in hours, that each item will be in use. Multiply the current in amps for each item by the number of hours it will be in use. That will give you the "power" it uses in Amp-hours (Ah)

Finally add all these Ah figures together to give the total consumption in Ah for a 24 hour period.

It would be wise to make estimates of running time closer to the maximum likely rather than the minimum.

A fridge will be difficult because it will only be operating for part of the time despite being plugged in all the time. It will also be dependent on the ambient temperature.

In some case you may have to actually measure the current if you do not have sufficient information without.

Next you will have to carry out a similar exercise for all your sources of electricity. Engine alternator output, a realistic figure not the maximum, multiplied by the time, in hours, the engine will be running after allowing a period to replace what is used in starting.
Solar panel output again a realistic figure and an realistic figure for the number of hours it will be in full or nearly full sun. Likewise for the wind generator.

Add all the outputs in Ah hours together.

If the total generated exceeds the total consumed you are a happy bunny. If the other way round then you have to consider economies in power usage or think of ways to increase the power produced. More engine running, bigger or more solar panels, bigger wind turbine, portable generator, shorepower etc.

Engine alternator is self regulating. Large solar panels and wind turbines need a regulator between them and the battery(old types use a shunt to dump excess power, modern ones are what is called "pulse width modulated", a bit of electronic wizardry that only the electronic wizards understand). Combined regulators for wind plus solar exist.

An in car charger will deal with you mobile phone. Don't know about laptops but I'm sure there must be some bit of electronic wizardry that allows you to run them from 12 volts Don't forget to include the laptop in the original calculations or better leave it at home!


Let the criticisms and arguments begin. Only constructive criticism allowed!

 

[Ifraser]

Not really concentrating on th post as a whole here but I noticed the bit about running a laptop from 12v... the simplest solution seems to be a 300w inverter from maplin for under £20... just converts 12v into 240v... and can be used for portable radios as well.. cheers Iain

 

[William_H]

If it is a boat new to you and you are new to boating do nothing...
Just use the boat and get some experience of your actual boating style.

Don't under estimate the power of an engine driven generator. For many years sailors have relied on the engine generator. It is only in modern times that fridges have come to demand more power. (possibly also the TV, lap top and chart plotter.

If you have a decent sized dual battery set up so that you have backup engine starting and you monitor the battery voltage to know when it is getting low you will be able to manage quite well. Don't leave the fridge on overnight, perhaps start with fridge on only with engine running.

If you use the boat often with plenty of engine running you won't need solar or wind power. A smart charge regulator might give you more charge for limited engine running time but is not necessary.

Solar panels can keep the battery healthy if you are away from the boat for long periods. A battery charger running from mains can be good if you are at a marina.

Yes there are lots of expensive gadgets to enhance your power management but just get some boating in first and slowly decide what you need. good luck olewill

 

[charles_reed]

An interesting theory William. Whilst I don't doubt your facts I have to take grave exception to the conclusions.

My boat uses 48 amp hours when at anchor in 24 hours at 24C peak ambient, that does not include recharging the computer, which, since attaching a Huawei dongle, for 3G access, has halved its battery life from 8 to 4 hrs. To fully recharge the batteries after 24-hrs use I need to run the motor for 50' (and that's with an 100amp output alternator not with a skinny 35 amp alternator fitted to most small boat diesels). To recharge the computer from 10%, requires 120' on the inverter @ 8amps, if the computer is on, that doubles. It needs 1 amp less on the solid state device.

As I can't stand warm beer the fridge is on - that uses 4.5amps when running (6 amps on start up) and runs about 20' in 300' during the day.

Under way the the consumption is increased by 18 amp hours in 24 by the autopilot, and 17 amp hours in 24 by the masthead tricolour.

At a guess our poster, IF LIVING ABOARD FULL-TIME, will need about 90 watts solar input (if at less than 45 degrees N or S) and a wind-generator of about 100 watts peak. At higher latitudes correspondingly more photovoltiac capacity.

If he's keeping the boat in a marina, using it only at weekends and keeps his batteries from ever dropping below 12v resting, I'd reckon he'd best fit a smart charger (switch-mode is the most common) and plug into the shore-power.

If the engine on the boat is more than about 5 years old, he'd be well advised to fit a smart regulator as well. The more modern regulator on board the alternator are slightly more effective than their predecessors.

Still we're all shooting at invisible targets, as he gives no inkling of intended mode of use.

 

[sausage]

Great response everyone, thanks! Ok, so a little to think about, and it seems mainly around ensuring the existing alternator is replaced with a more efficient one, a regulator, and 100 watts of wind and 100 of solar.

A good starting point for investigation.

I will be living aboard, and plan to cruise down to the Med and spend my time there. Ideally only at Marinas when really needed so to be able to power oneself as long as possible is highly diserable. I would rather not rely on running the engine to charge my batteries.

The invertor looks useful for whilst Im on the move. As does another device called the "Solar Gorilla". I heard the inventor interviewed on Radio 2 and he claims it can keep a fully charged laptop in operation for 4 days. Obviously this depends entirely on the laptop, but it could be a good augmentation to power supplies.

Thanks again,
Mark