Power Audit for livaboard

[Maxi_10]

We have bought a boat and plan to liveaboard from next April. European west coasts followed by Caribbean in about a years time.

I am just planning for winter re fit work on the boat, an Oyster 42.

If anyone has the time, experience and knowledge could they check over my power audit and power generation spreadsheet attached. Have I made an basic errors or wrong assumptions?

The first sheet Existing shows power use with the boat as it is both under sail and at anchor. The second estimates the power use after changing lights to LED's and adding a windvane self steering.

The power generation section on each sheet shows how many hours I would have to run the engine to replace the power used, how many hours I would have to run a generator to do the same. The the third option is to fit a wind generator and 140 w of solar panels, use these plus run the engine, if required, to make up the balance.

Does it make sense and does it add up? any thoughts welcome.

 

[GrahamM376]

Theory is all very well but, in practical terms on our 38ft boat, this is what I find.

200W of (tilting) solar panels plus Aerogen4 mounted on gantry, feeding 2 banks of 260AH domestics + engine start battery is just sufficient in Algarve sun and temperatures to keep us going on mooring/anchor without having to start the engine or use the genny. We can just manage for 2 overcast days.

The fridge (Danfoss BD50F compressor with large "O" freezer compartment) is the biggest draw at around 7.5 amps when running. Anchor and all interior lights are LED. Good sun allows netbook computer to run through inverter all daylight hours and some LCD TV in evenings.

Running the engine for battery charging is bad news as it glazes the bores, much better to use the genny + battery chargers when needed but, NOT in the evenings and only when absolutely necessary during the day - very antisocial behaviour!

 

[noelex]

Well done on making a power budget.

A few of comments:

The figures for solar are only achievable in a good summer climate. In Greece for example, which has high insolation values, your 140w would give you an average of 60AHrs in summer, but only 21 AHrs for winter.
The wind generator figures also look optimistic, depending on location

Your autopilot uses much more than most if your figures are accurate.
Your VHF draw is low most consume 0.5-0.75A
LEDs generally use a bit less power than you have estimated These are going to pay for themselves very quickly.

 

[lenseman]

On your second pdf you state 140W = 120Amps and go on to state 50% = 60Amps

I think the correct 50% figure assuming full sunlight all day should be nearer 5.83 Amps?

 

[Maxi_10]

Thanks for the early replies.

Practical experience doesn't seem too far wide of the theory and adds to my understanding, danger of use of engine and antisocial possibilities noted. It may be I only need to do this when sailing 24/7, so not that often. Hope to follow the sun so should get good return from solar.

I have had another look and the autopilot figure is probably too high, difficult to measure as the actual use on a meter jumps around as the rudder is moved and its not the only thing running. Other users have reported a figure nearer 2.5amps average so I will go with that.

VHF agreed, LEDS there are lots of them hence the figure.

Apologies as a non engineer non technical person I have missed some stages and probabaly used the wrong units what I meant was:

140 w at 12v = 12 amps, run for 10 hours = 120 amp hours at 50% effeciency give 60 amp hours per day into the battery. or am I still wrong?

 

[dougg]

If its of any use, we are 42ft in the med with an air breeze and 130w solar and its just not enough to keep our 440 amp battery bank full. Next year I will add another 130w maybe 260w.
IMHO Your fridge will run for longer than you think!

 

[charles_reed]

My experience in Greece, high summer, is that with 235ah of battery bank in use with 318 w of PV panel controlled by a MPPT controller, I can enjoy 10 days, anchored which drops to 5 days using a CULV computer.

In comparison with the fridge and computer everything else pales into insignificance and, if you rise with the sun and bed when it goes down, LED lighting is not worth the capital cost, especially as their is little to choose in consumption between fluorescent and warm-white LEDs in consumption/light output.

With a smart alternator controller, your batteries will soon be topped up especially in W and Central Med.
In the E Med it can be a different picture with wind making the sails the primary means of passage.
In fact one needs both wind and PV generation and, monthly, 24 hours or so with shorepower to put an equalising charge into the batteries.

PS Be aware that it's almost impossible to mount PV panels on a boat to maximise insolation, so a theoretical 50% efficiency is impossible to achieve unless you are prepared to act as a surrogate sundial and constantly adjust the panels.

 

[sailinglegend420]

First I would suggest that one winter is not enough to fit and test what you need - we spent 4 years before we left the UK.

If you are using your engine to charge the batteries you will only ever reach 80% charge that's 120Ahs available not 140Ahs - maybe splitting hairs - but it does very quickly suggest that you need more battery capacity because running an engine or a genny every day is a no brainer. Using a 56 HP engine - or bigger - to charge your batteries when a 5 HP genny would do the job is just crazy - but even then you don't ever achieve 100% charge. Try and work on at least 4 days at anchor before having to run an engine or genny, because by then you may be moving on anyway.

Consider changing the engine start for a small red flash battery and use the space for another service battery. Also consider getting AGM batteries which will charge twice as fast as wet cels, but you must go for a much bigger alternator - 120 amps.

More solar power is also an answer.

Agree with all the other comments, but LEDs are good if you buy a dozen at a time - but do get an LED for the anchor light.

 

[lenseman]

Another small detail which is in your favour is that you have allowed 10 Amps for SSB.

As a radio amateur of many years standing, I can assure you that you will not be using 10 Amps except whilst you transmit SSB at the full 125 watts PEP!

Most of the time (~90%), you will be listening and not talking and the current drain will be far less, probably less than 1 Amp.

Another very good 'trick' which is useful, not only with SSB but with marine VHF or any radio including broadcast band for Radio 2 or Radio 4 even, the more the volume is turned up, the shorter will be the battery life, be it the 12-volt house batteries on your boat or the 4 x AA's you buy in town. The trick is to use headphones. You will find that a set of good quality cushioned headphones (or earpieces for small portable radios) will make listening to the HF bands so much more 'pleasurable' including the fact that the audio stages of the radio will be disabled saving you possibly ¼ to ½ Amp drain from your 12 volt system.

 

[sailorman]

First I would suggest that one winter is not enough to fit and test what you need - we spent 4 years before we left the UK.

If you are using your engine to charge the batteries you will only ever reach 80% charge that's 120Ahs available not 140Ahs - maybe splitting hairs - but it does very quickly suggest that you need more battery capacity because running an engine or a genny every day is a no brainer. Using a 56 HP engine - or bigger - to charge your batteries when a 5 HP genny would do the job is just crazy - but even then you don't ever achieve 100% charge. Try and work on at least 4 days at anchor before having to run an engine or genny, because by then you may be moving on anyway.

Consider changing the engine start for a small red flash battery and use the space for another service battery. Also consider getting AGM batteries which will charge twice as fast as wet cels, but you must go for a much bigger alternator - 120 amps.

More solar power is also an answer.

Agree with all the other comments, but LEDs are good if you buy a dozen at a time - but do get an LED for the anchor light.

Taken from the Oyster Forum

Just a thought from our own experience and what we saw in the ARC last year -

IF you can get away without fitting a diesel generator, then you will not only save the internal space and fuel, but will also be far more self-sufficient in the Caribbean. On your size Oyster I, personally, would try to achieve eco-friendly power generation, if possible.
This would mean fitting extra batteries, probably, to double your capacity to at least 430 AmpHours.

We have had very good experience with gel cells so far, with our non-stop usage of our Oyster 56 living aboard full-time.

We have also had very good experience with the Cantalupi LED light fittings we have got all round our interior. They are great for low power consumption, low failure rates and low heat output, but you may find these expensive to change over from existing?

You should read the earlier strings on the Oyster Ownets' Blog ref LED lights, I guess!
Oyster made a recommendation on these at the end of the string.

If you are smart with your electrical usage and only make light use of an inverter for 220V AC equipment, i.e, no Aircon and no washing machine, then an eco-friendly solar and wind / water generation system could work for you.

If, however, you MUST have these two items and/or want a 220V AC watermaker, then a diesel genset becomes your only option, unless you wanted to risk trying out the New Zealand made and Dutch marketed Sterling Engine generator (Whispergen?), which an Oyster client tried out for himself several years ago with varied success.

There was, for the first ever European unit installed, a lot of support from the NZ manufacturer required, but they may well have sorted all this out by now. One would certainly hope so! If now fully proven, it could justify your looking into that again for your Oyster, as it could suit a 42 well?

The key with eco-friendly generators, however, is to be able to fit kit which is noise and vibration free AND to avoid being always reliant on just one source of power, e,g. wind. Wind generators are notoriously useless downwind, for example. Solar panels need to be free to angle towards the sunlight on whatever tack you are. Older, cheaper wind generators also were noisy, but I have now seen and heard far better ones in use, which seemed to be very acceptable indeed.

The newer Rutland 913 and AirBreeze wind generators appear to be far better and quieter than they used to be. If you can find somewhere to mount them, perhaps by fitting a stern-mounted SS arch (which could also then take a radar and /or a bimini fitting, too) then you will be creating a space and load-bearing structure that could have solar panels and wind generators all fitted at the same time.

The problem with this solution (as there always are problems / compromises in all your choices) is that you will be adding considerable weight and visual height aft. This needs to be done carefully, so as not to end up looking very odd in the water!

You should also consider how it might affect your plans for stowage of a RIB, or dinghy. Will it incorporate davits or a lift system on the transom arch, in which case that is more weight aft? This will seriously affect trim.

All the best with whatever way you choose to go.

You definitely should try to get a watermaker installed, if you can work out how best to power it. You are not free from marinas and expensive berthing unless you have one.

By the way, the point made about SSB radio being only for those who are super-sociable is a good one, but an SSB, if you are sociable and also sailing long distance, is still a superb piece of kit, and one I have not regretted. Apart from radio chatter, however, if you do not plan to have Sat-Phone access, but want to be able to download weather files and forecasts, then getting Navtex and/or Isobar weatherfax files via SSB is fairly easy and can be very comforting when deep sea!
You can also listen in to all sorts of radio stations, as well as being able to use it for safety transmissions.

For advice on retro-fitting electronics, WiFi, stereo, TVs, computing and communications you should consider contracting Gavin Painter, of 'It@Sea', who works out of an office near the Hamble. His expertise in all this, on Oysters, is without compare.

gavin painter <gavin@it-at-sea.com>

PS. Whilst writing this from IGY's Newport Marina in New Jersey and looking out over downtown Manhattan in New York by sunset, after a full summer cruising Nova Scotia and Cape Breton Island, Canada and then down to the US East Coast, I would say these are truly great cruising grounds, even if a bit expensive if you hit the bigger cities. With care, though, one can anchor in lots of places.

Nova Scotia and Maine are simply wonderful places to cruise gently and slowly.

PS. all the East Coast now tends to require WC Holding Tank installations, so please ensure you do have good, large, gravity holding tank(s) fitted. There are also lots of nice anchorages in the Caribbean where one's swimming and snorkelling are only really kept nice by use of a holding tank!

 

[TQA]

I am a liveaboard and find 400 watts of solar keeps my 675 ah bank fully charged.

I run
fridge 24/7 Adler Barbour Supercold Machine [DBs]
SSB
lights not LED
VHF
Lappie a lot
AP

Once or twice a year I need to run the engine for charging purposes after a prolonged dull spell.

Location Windies.

 

[Maxi_10]

Thanks to all who replied.

I have refined my audit based upon advice recieved, I need less power than I thought but wind and solar seem to produce less then anticipated as well.

Absolute power security can only be provided by a diesel generator and wind/solar. I just need to work out what I can afford now. If its only diesel or eco then that will probably do 90% of the time with the engine filling the gaps.

Interesting that LED's are not the must have that i thought they would be.

 

[GrahamM376]

Interesting that LED's are not the must have that i thought they would be.

Much depends on whether you are a marina dweller or prefer anchoring. Your battery capacity and charging regime will dictate what you need. For us LEDs are a must, we are rarely on shore power - we could have 10 on (if we wanted) for the same current draw as one 12W bulb. Fluorescent lights have similar draw but seem to attract the mossies more.

 

[Roberto]

Battery capacity

IMHO, the most sensible thing to do first is to increase battery capacity.

Example (sorry could not download your documents)
Say you have a daily budget of 100Ah, you might decide (just to show the extremes):

1. Fit a 200Ah battery, discharge it 50% daily and accordingly (try to) recharge 100% daily. You would end up with endless engine/generator hours, or would need solar panels the size of Trafalgar Square; *plus* your batteries would hardly be charged 100%. Most if not all charging systems are regulated, meaning that once battery voltage is say around 14ish (depending on type) they would begin cutting current and increasing remaining charging time. Night comes and solars are out, for example, or a neighbour/resto of family complains about the genny, etc etc

or

2. Fit a 500Ah battery bank. You could use the battery in the interval 60%-80% discharge/recharge cycles (65-85, whatever). Whatever you use as charging means, begin charging at 60-70% means it would work a lot more efficiently, an alternator would give the highest current batteries can take, ditto solar, etc. The same 100Ah would be recharged in *a lot* less time than with solution 1.
Once every so often plug into a shore charger and leave long enough to recharge everything 100%, just for battery health.



Btw, this second hypothesis is about our case, 500Ah battery, 180W solar, 90A alternator; without sun, when batteries are 60-70% down the alternator outputs 50-60 A for between one to two hours, that gives roughly the 100Ah we need; with good sunshine the panels allow us to use the engine every 4-5 or 6 days, which we usually do anyway when we move anchorage

 

[sailinglegend420]

The right LEDs are good

Thanks to all who replied.

........Interesting that LED's are not the must have that I thought they would be.

I hope I didn't give the impression that I agreed with a previous poster about his rejection of the LEDs at not necessary and too costly. Note that he needs 318 watts of solar - probably just to power his anchor light each night. Don't take all the postings on this forum as fact - including mine - check out for yourself, you seem to have done a very good job so far.

One extra thought on LEDs - which we have- is that a 10 watt G4 tungsten needs a lot more than a 10 watt LED because the reflector in the light fitting has no effect at all when LEDs are used. 25 watts would be better - but its more down to the lumens produced and the angle of light spread. We were disappointed with our first LED purchases so had to spend more to get better light. Things are changing quickly so what we bought 4 years ago won't be the best now. You'd be better finding a boat who has done the changes and is happy.

 

[duncan99210]

We changed out all the G4 halogen bulbs on Rampage for LEDs (24 diode flat 'plaques') year before last. The bulbs were 10 watts, the LEDs are about 1.8 watts. They give a yellower light than the bulbs (more pleaseing to the eye), enough light to do things by in the evening, they're cool to the touch and use less than a quarter of the power. They have a polarity sensing chip in them, so it doesn't matter which way round the supply is connected and have given us no trouble at all.
They were bought off Ebay for about £2.50 each and were shipped direct to Spain from the factory in China. I'd recommend them to anyone - only problem is I can't remember which ebay shop I bought them from! I recently bought some more for a cockpit light - they were not as satisfactory as the first lot, as they are a much bluer colour, but even cheaper than the first lot at about £1.50 each!

 

[jimking]

Hi

I am currently sitting out the hurricane season in Grenada. If I can get 10 amps per day out of my Air Breeze generator I think I am doing well. It does improve over the winter. If you have room to fit them solar is the way to go. Ensure that you have an MPPT controller as you can gain up to 30% extra output. You will need a minim of 300 watts. Remember in the Caribbean the water and air temperature is always between 80-90F so expect to use more amps for your fridge. I would ignore Western Europe in your considerations as you will find that quite often there is no choice but to go into a marina, once in the Caribbean you will want to anchor as much as possible to get a breeze through the boat., hope this helps. Most people fit Kyocera panels as they seem to be the most efficient (16% compared to 14%)

Jim

 

[jordanbasset]

IMHO, the most sensible thing to do first is to increase battery capacity.

Example (sorry could not download your documents)
Say you have a daily budget of 100Ah, you might decide (just to show the extremes):

1. Fit a 200Ah battery, discharge it 50% daily and accordingly (try to) recharge 100% daily. You would end up with endless engine/generator hours, or would need solar panels the size of Trafalgar Square; *plus* your batteries would hardly be charged 100%. Most if not all charging systems are regulated, meaning that once battery voltage is say around 14ish (depending on type) they would begin cutting current and increasing remaining charging time. Night comes and solars are out, for example, or a neighbour/resto of family complains about the genny, etc etc

or

2. Fit a 500Ah battery bank. You could use the battery in the interval 60%-80% discharge/recharge cycles (65-85, whatever). Whatever you use as charging means, begin charging at 60-70% means it would work a lot more efficiently, an alternator would give the highest current batteries can take, ditto solar, etc. The same 100Ah would be recharged in *a lot* less time than with solution 1.
Once every so often plug into a shore charger and leave long enough to recharge everything 100%, just for battery health.



Btw, this second hypothesis is about our case, 500Ah battery, 180W solar, 90A alternator; without sun, when batteries are 60-70% down the alternator outputs 50-60 A for between one to two hours, that gives roughly the 100Ah we need; with good sunshine the panels allow us to use the engine every 4-5 or 6 days, which we usually do anyway when we move anchorage

Very similar set up to us, 560 Ah battery (domestic) and just aquired 200w solar. Only had this in full operation for a couple of weeks but more than happy. We did not need to run the engine just to charge the battery but only had 4 consecutive days days at anchor during this period. Battery at the lowest (8am in the morning) still showing 75%, 12.6 v. During the day went close to maximum again. We have gone for LEDS, use a fraction of the energy of our previous halogen ones

 

[GrahamM376]

Hi

I would ignore Western Europe in your considerations as you will find that quite often there is no choice but to go into a marina,

Plenty of anchorages from Ushant to Gib, although limited on Portuguese west coat.