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Old 02-08-2020, 19:16   #61
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Re: Could someone check my math please?

$400 to fill my water tanks!?!?! Blooming heck I had NOT thought about that one. Itís all free and really high quality around Northern Europe. I knew there might be quality issues elsewhere and have a filter unit lined up to handle that but expensive I had not thought of.

As far as usage goes, from personal experience I know that if we use salt water for dish washing our tanks last me and SWIMBO about two months. With the kids on board and just using the water like it is free and easy to get hold off (like it is here), they last us about 12 days.

Iíll think about the water maker.
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Old 02-08-2020, 19:20   #62
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Re: Could someone check my math please?

Also, donít you have to lug fuel?
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Old 02-08-2020, 19:48   #63
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Re: Could someone check my math please?

So let’s say that I do get a water maker and swallow the 4000 euro price tag �� and let’s say we use it to meet all our water needs and that we use about 30l a day because we have stopped being so water conscious because we have a water maker. A 12v dc unit delivering 20-30l requires 9 amps. So let’s be conservative and say the water maker needs 15Ah a day. That is not much compared to the autos 80-100ah, the heaters 50Ah or the fridges 40 ah..

I wonder if the water maker and a 12v water heater can be set up to be power dumps once the batteries are charged for the days when you are producing more power than needed?
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Old 02-08-2020, 20:47   #64
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Re: Could someone check my math please?

Sort of. The hard part is that the water maker is going to pull faster than most solar puts in, but.... You could plan to only make water on days you've filled your batteries by say 1 or 2 pm...
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Old 03-08-2020, 02:12   #65
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Re: Could someone check my math please?

And here is why I donít really see the need of davits. The dinghy launches from the boom with little more faff than from davits and stows upside down or right side up nicely on the pilot house roof where it has zero impact on any of the boats operation except that it stops you from cracking open two hatches in the pilothouse. I wouldnít cross oceans with it there but neither would I want to cross an ocean with a dinghy bumping around on davits ( Iíve done that and not only was it annoying but we did get one wave that struck the dinghy and nearly pulled out the davits)

So really I would only be getting davits to put solar panels on them. Seems a bit pointless to me.

However, this spot is also prime real estate for solar panels. The dinghy actually sits on the hatches and doesnít touch the deck so it wonít damage panels here but of course it would make them useless when under sail or if we are too lazy to put the dinghy back in the water on arrival. But then many of you seem against mounting panels there anyway due to shading and efficiency issues.

If Iím not putting panels on and Iím not wanting a rib then I see no need for davits beyond as solar panel mounts and then I might as well do an arch, which I am loathed to do mainly for aesthetic reasons ( I can see 4 boats with arches from where I am sitting and the arch does none of them any favors in the looks department, but I acknowledge that beauty is in the eye of the beholder).

So after all of your comments and much thinking this is where I am at.

1. I should count on consumption of 200Ah a day under way and 100Ah a day when stationary.

2 Therefore, I need to generate about 12OAh a day at anchor and 240Ah a day underway on average to give me a safety margin.

3 My battery bank needs to have sufficient dispatchable Ah to meet highload items such as watermakers and heaters and also to cover days when generation lags consumption. Letís say I need 300 dispatchable Ah. That would seem to entail a FLA bank of about 900Ah (which I do have the space for) or 400-500 Ah lithium with AGM and Gel somewhere in between.

4. A hydro generator would meet all my needs underway an average at the cost of 0.25 kn of boatspeed (I can live with that) and quite a lot of faffing around (more of an issue) and at quite a high cost / generated Ah ( less of an issue)

5. I can maybe fit 200 W of solar easily above my radome that can give me maybe 100Ah a day at a very low cost to generated Ah and close to zero nuisance to me.

6. I could fit an additional 220 W of solar on the pilot house roof but this would suffer from some shading and interfere a bit with dinghy handling. It might not return more than 50Ah a day in reality due to shading and heat induced inefficiency and so would be quite high cost generation.

7. I could add a wind generator on the aft port quarter but am likely to be disappointed by its output and annoyed by its noise (having said that I was recently moored beside a six blades generator and I honestly could not hear it turning).

8. I could add a second alternator or replace the existing to up the output under engine to in the region of 150Ah at a cost of about 5hp out of 90 (I can easily live with that).

Items 3 and 5 seem like no brainers to me. 8 is also easy but I would really rather meet my electrical needs with as little input from the engine as possible so I am going to hold fire on that and see if itís necessary. For me 4 is also a no brainer. If Iím moving at more than 5 knots then Iím generating enough for my needs underway and my boat moves at more than 5 knots in anything over a force 2. Usually when itís less that that itís sunny and the solar can pick up the slack. 7 and 6 seem to be the most dubious options. Iíll need to think about them further.
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Old 03-08-2020, 07:19   #66
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Re: Could someone check my math please?

Quote:
Originally Posted by Na Mara View Post
And here is why I donít really see the need of davits. The dinghy launches from the boom with little more faff than from davits and stows upside down or right side up nicely on the pilot house roof where it has zero impact on any of the boats operation except that it stops you from cracking open two hatches in the pilothouse. I wouldnít cross oceans with it there but neither would I want to cross an ocean with a dinghy bumping around on davits ( Iíve done that and not only was it annoying but we did get one wave that struck the dinghy and nearly pulled out the davits)



So really I would only be getting davits to put solar panels on them. Seems a bit pointless to me.



However, this spot is also prime real estate for solar panels. The dinghy actually sits on the hatches and doesnít touch the deck so it wonít damage panels here but of course it would make them useless when under sail or if we are too lazy to put the dinghy back in the water on arrival. But then many of you seem against mounting panels there anyway due to shading and efficiency issues.



If Iím not putting panels on and Iím not wanting a rib then I see no need for davits beyond as solar panel mounts and then I might as well do an arch, which I am loathed to do mainly for aesthetic reasons ( I can see 4 boats with arches from where I am sitting and the arch does none of them any favors in the looks department, but I acknowledge that beauty is in the eye of the beholder).



So after all of your comments and much thinking this is where I am at.



1. I should count on consumption of 200Ah a day under way and 100Ah a day when stationary.



2 Therefore, I need to generate about 12OAh a day at anchor and 240Ah a day underway on average to give me a safety margin.



3 My battery bank needs to have sufficient dispatchable Ah to meet highload items such as watermakers and heaters and also to cover days when generation lags consumption. Letís say I need 300 dispatchable Ah. That would seem to entail a FLA bank of about 900Ah (which I do have the space for) or 400-500 Ah lithium with AGM and Gel somewhere in between.



4. A hydro generator would meet all my needs underway an average at the cost of 0.25 kn of boatspeed (I can live with that) and quite a lot of faffing around (more of an issue) and at quite a high cost / generated Ah ( less of an issue)



5. I can maybe fit 200 W of solar easily above my radome that can give me maybe 100Ah a day at a very low cost to generated Ah and close to zero nuisance to me.



6. I could fit an additional 220 W of solar on the pilot house roof but this would suffer from some shading and interfere a bit with dinghy handling. It might not return more than 50Ah a day in reality due to shading and heat induced inefficiency and so would be quite high cost generation.



7. I could add a wind generator on the aft port quarter but am likely to be disappointed by its output and annoyed by its noise (having said that I was recently moored beside a six blades generator and I honestly could not hear it turning).



8. I could add a second alternator or replace the existing to up the output under engine to in the region of 150Ah at a cost of about 5hp out of 90 (I can easily live with that).



Items 3 and 5 seem like no brainers to me. 8 is also easy but I would really rather meet my electrical needs with as little input from the engine as possible so I am going to hold fire on that and see if itís necessary. For me 4 is also a no brainer. If Iím moving at more than 5 knots then Iím generating enough for my needs underway and my boat moves at more than 5 knots in anything over a force 2. Usually when itís less that that itís sunny and the solar can pick up the slack. 7 and 6 seem to be the most dubious options. Iíll need to think about them further.
I'm chiming in a bunch cause once we get our new boat (hopefully this week/weekend Survey is Wednesday) I'll be doing some similar.
Replies to your numbers.
1. Close enough. Always assume high.
2. Sounds about right.
3. Careful with old style and not charging fully etc. If you're not making enough power for whatever reason, whale hits your hydro, clouds, eternal darkness, whatever, they might not charge enough to be happy then it'll be a process to recondition etc.
4. The logic on hydro seems sound, but that's a lot of money for no return when anchored. It'll power the autopilot, which is good, but I'm inherently cheap, even though I think they're awesome.
5. Wonder if you could rig up lines to help that pole under heavy wind conditions and maybe one support like a gusset? Then possibly go to 300-400w on that single pole.
6. This might be a place for flexible panels. Mount them on some thing that allows air flow. (In the states the "corrugated" plastic they use for stupid election signs are great. Wait till election is over and ask losing campaigns and free supplies...) Have that mount so you can quickly adjust and it'll go right over the dinghy when on board or on roof when the dinghy is in the water. You could probably easily fit 4 100w panels setup to two controllers. (Port/starboard) and that would help a bunch.
7. I'd skip the wind generator. My boat has one, and everyone I've talked to about them says "add more solar". I'll have it. It'll be there.
8. Bigger alternator is a good idea for a "oh crap a whale hit the hydro and a blimp is sitting over me for permanent shade. No one wants to use the engine, but having it as a backup is a good idea.

I also agree that some arches seem to be trying to look like a wake board boat. Saw one that even had giant speaker pods mounted. Sigh. From fishing lakes I hate any boat with more more speakers pointing away from the boat than in the boat.
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Old 03-08-2020, 07:50   #67
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Re: Could someone check my math please?

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Originally Posted by Na Mara View Post

I’ll think about the water maker.
We sailed twice around the world without a water maker - never had an issue, never paid any outragous price for water - yes we did jug water a few places (but not that many). We caught rain very effectively, and we were light users (dish wasing in salt and such). We carried 800lts in tanks, plus some extra bottled water.

So . . . . while they have popularly been moved into the 'must have' list for many people and I understand the arguments . . . . they are in fact an optional choice and you can cruise in a perfectly civilized fashion without them.

Im sure you know this, but you need to be a little careful, otherwise you will end up with an overloaded and way too complicated boat. Keeping the boat simple is a priority you will see and hear from many of those who have gone long distances/times - it improves reliability, it reduces frustrations of repairs, less clutters creates good access which improves reliability - and it improves sailing (lighter and less cluttered).

On your 8 above . . . . you should at the very least put on a decent size (like 120 amp) externally regulated alternator. There is essentially no downside to that and lots of upside.
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Old 03-08-2020, 09:41   #68
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Re: Could someone check my math please?

Hscrugby,

It’s thanks to all your helpful comments, and those of other, that I have come so far in my thinking.

Maybe some flexible panels I can throw over, dinghy, pilot house, or even our cockpit tent (which doubles as an in harbour bimini) are a good idea. With solar as cheap as it is there is probably no down side to that other than having to store them when not in use. I doubt that is much of a problem.

Breaking wave.

I try, I really do try, to be a devotee of the KISS philosophy. Hence no genset (despite having a big well insulated, engine bay that would easily swallow one), no electric winches save the windlass and inmast reefer (though I do have an ewincher for those lazy moments), no electric toilets ( I’ve removed both of those and replaced them with manuals with locking pumps), no electric solenoid on the gas (a mechanical leak detector in the locker and a manual shut off valve under the cooker), and so on.

But the temptation is always there isn’t it. I could electrify the foresail reefing drum. Why dont I do that when I replace the nearly done furlex. Isn’t a manual furler on a boat like mine with electric inmast a bit silly. And then SWIMBO wants stern thrusters. No matter that SWIMBO also prefers anchoring and wants to spend 90% of the time anchored or underway. And never mind that I have patiently explained to her that a 43ft fin keel yacht with a 7hp bow thruster and a 90 hp engine operating through a reversing prop needs a stern thruster like a fish needs a snorkel. Then there’s the 24 inch TV that the kids had to have, all the charge points everywhere for everyone’s favorite devices, and so on and so on.

Finally, though I have sailed for nearly 40 years and done some big boy stuff during that time I’ve never crossed the Atlantic nor lived aboard for more than 2 months at a time. So I take seriously the advice of those who have that experience and much of that is of the variety “you’ll need widget X for reasons Y and Z. Whatever you do don’t get widget P! “.

And so my practice of KISS falls somewhat short of the level of devotion the creed warrants. I keep telling myself that I will do better. Maybe I will even mange it at some point
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Old 03-08-2020, 15:57   #69
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Re: Could someone check my math please?

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I really do try, to be a devotee of the KISS philosophy. . . . .But the temptation is always there isn’t it.
Yes, exactly.

We have done a massive amount of 'serious' cruising - and I would suggest IMHO the only two actually necesary pieces are:

(1) self steering with comprehensive spares/back-ups. Having to steer for a week by hand sucks. And there are a lot of bits of an autopilot which will brick it if (actually more accurately when) they fail - like the rudder reference indicator and the fluxgate. And it all wants to be accessable enough that you can swap parts in a seaway. On a transit your self steering is going to be working 7x24 for like 3 weeks - that's a lot of hours and fatigue cycles.

And (2) a 'big enough' anchor and rode. 'Big enough' means you can sleep well even when you have a forecast for 40kts.

Beyond that is balancing the needs of 'reliability' and 'comforts'. Often those two are in partial conflict. We ourselves strongly prioritized reliability- prefering to adapt our life style to become 'iron men' (note:that is a historical reference to tough as nails seamen). While others we know bring all the comforts of home.

Thats a bit offtopic, sorry

On-topic . . . . you essentially already have an ice genset - your main engine. You have just crippled it by not putting the best alternator/regulator set-up on it. Your choice ofc. But you will be motoring, at the very very least in and out of harbours (and if you follow common practice once you get 'out there' rather more than that. And I would suggest since you already have 85% of a great generator it makes super sense to take care of the remaining 15% so that it does in fact charge super well when it is being used.

Another small aside . . . .I dont know how much deep ocean swell you have sailing in . . . . but it is rather harder to sail well in light airs when a big swell is rolling the guts out of the sails - it is one reason people motor more than they expect. Modern weather tools have given people the capability to (mostly) dodge storms and (often) head winds . . . . but only if they keep their average speed up when they need to, and often there can be a somewhat light zone leading a storm . . . .which again often means a bit more motoring. And finally despite all the possible calculations . . . . there often seems to be a need/desire for a bit more power - or perhaps its just people tend to spend their budget plus a bit and since the wind is 'light or forward or something else not perfect' it is a god time for a bit of motor assist/mtor-sailing. It just happens. Yes there are a few who resist it, but relatively few.
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Old 03-08-2020, 22:02   #70
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Re: Could someone check my math please?

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.....Are my generation numbers realistic?
COULD SOMEONE CHECK MY MATHS PLEASE is the title of the thread.

Lots of good opinions offered but I offer comments on your math.

An FLA bank has a "charging efficiency" of maybe 85% - that's an average figure used by a battery monitor - which means if you want to put 100Ah into a bank then about 120Ah are needed - so a 20% shortfall in your math here!

Not many people realise that "charging efficiency" is also dependent on the % charge of the batteries - so the 85% quoted for FLAs is an average figure for discharging to 50% - where the charging efficiency is nearly 100% - and then recharging to 100% where the charging efficiency is very very low. If you intend to recycle down to only 85% SoC the charge efficiency may always be as low as 50%. This means for every 10 amps of charging current only 5 amps are are doing useful work. See chart attached from Sandia National Laboratories, Photovoltaic System Applications Department...

Battery "Charging efficiency" is very different to the battery Charge Acceptance Rate which is the amount of current that a battery will accept at a given voltage and given state of charge. This decreases rapidly as the batteries get more fully charged. These two factors are why charging from 85% to 100% can take 10 times longer than charging from 50% to 85%. It is also very important to understand why charging to 100% is so important and how to determine what 100% is - it's not when your battery charger says FLOAT! Lots of other threads here on this.

All these points here can dramatically change your calculations - so 600Ah bank should be a minimum - 450 watts of solar would be good - look at semi flexible panels which are much more expensive but can be mounted anywhere and walked on.

And make sure you instal a battery monitor to check the charging currents of these devices - and so that you can accurately calculate the Ah usage each day/night. But be aware that battery monitors are routinely installed incorrectly and programmed incorrectly or new kit is added later that does not go through the shunt.

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Old 04-08-2020, 06:44   #71
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Re: Could someone check my math please?

Many thanks Sailinglegend.

Its exactly this kind of comment I am after.

I plan to mostly stay above 80% charge on the batteries so I have a reserve for when there is a dearth of generation. 50% charge efficiency in that zone is a real bummer.

1. Would MPPT’s on the panels not help?
2. Would switching to lithium batteries help?
3. Apart from the upfront cost, is there any downside to lithium batteries?
4 I was going to put a pico battery monitor on the boat this year. How do I ensure that the yard installs the thing correctly or at least check this after the fact?
5. I can easily accommodate 600Ah of FLA batteries, and by nicking the bottom of a cupboard in the under saloon cabin I can get to 900Ah. We are five years out from the North Atlantic circuit. Is it worth putting all that capacity on now ( and how much of it) or should I make do with the present 375 Ah and switch them out just before we head off?

Many thanks again from Na Mara
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Old 04-08-2020, 06:53   #72
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Re: Could someone check my math please?

On the anchor and rode we carry a 20kg Vulcan on 40m of 10mm chain that can be extended using the bridal with 2x 40m of 12mm ,12 plaited braid. All of that is more or less ready to go. If it’s really going to blow I add a 20kg CQR on 6m of 10mm chain to the dedicated attachment point on the Vulcan for series anchoring. If its heading into storm or hurricane territory then I extend the bridal by as much as I feel necessary. The weakest link in the setup are the shackles rated at 4 tons breaking load.

I reckon the basic setup is good to about 40knots in a fair anchorage. Much past that and I’d go with the series setup, though it’s a PITA to set and raise.
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Old 04-08-2020, 10:07   #73
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Re: Could someone check my math please?

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Originally Posted by Na Mara View Post
Many thanks Sailinglegend.

Its exactly this kind of comment I am after.

I plan to mostly stay above 80% charge on the batteries so I have a reserve for when there is a dearth of generation. 50% charge efficiency in that zone is a real bummer.

1. Would MPPTís on the panels not help?

Always use MPPT - Victron cheap and very good with a free app.

2. Would switching to lithium batteries help?

I use Lifeline AGMs - the last one's (1050Ah) I replaced last year after 14 years.

3. Apart from the upfront cost, is there any downside to lithium batteries?

If there is a fire on board from say your engine then you will have a very hard job putting out the lithiums when/if they catch fire.

4 I was going to put a pico battery monitor on the boat this year. How do I ensure that the yard installs the thing correctly or at least check this after the fact?

Instal the original SmartGauge yourself and add a separate amps/Ah counter. The Balmar SG200 seems not to be working for a lot of people.


5. I can easily accommodate 600Ah of FLA batteries, and by nicking the bottom of a cupboard in the under saloon cabin I can get to 900Ah. We are five years out from the North Atlantic circuit. Is it worth putting all that capacity on now ( and how much of it) or should I make do with the present 375 Ah and switch them out just before we head off?

Go for the maximum you can - especially without lots of solar.
My comments in Red.
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Old 04-08-2020, 12:40   #74
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Re: Could someone check my math please?

The battery bank is literally less than 40cm from the engine and separated by one thin quarter height bulkhead and some noise insulation. Lithium is out then!!!

I had AGMs on the last boat and was advised against them as many get less than 3-4 years out of them while FLA,s can last decades if looked after (not sure I like the off gassing though).

You didn’t really answer my last question. Should I go all in with a bunch of banner marine 75Ah batteries to a total of 900ah now, or should I wait until just before heading out and replace my present 375ah with say 900 Ah AGMs at that point? Is it better to leave on new batteries or to run with tried and true ones?
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Old 04-08-2020, 14:15   #75
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Re: Could someone check my math please?

Nu Mara....there is way more going on here in your thread than I have the time to read, critique, and advise you on...
I thought you were just looking for some quick confirmations before you headed south, and across the Atlantic later this year...
Quote:
Originally Posted by Na Mara View Post
We are kitting up the boat for a North Atlantic circuit and I am now getting around to the electrical system.
But, you want a good deal more, and you have 5 years to go....so, after this posting, I'll move aside and let you do your homework..



First off a few quick things....This is what an MPPT controller is good at....and they do work great!!
Quote:
Originally Posted by Na Mara View Post
The x22 panel is a beast 60v output and 1558mm x 1045 mm in dimension. I’m looking for 12v charging so I’d need a control unit to step that voltage down a lot or much of the generation will be wasted.

Please understand:
a) ALL solar panels that you'll use have a higher voltage output than your batteries....(even a "12 volt panel" is not a 12 volt panel, it's an 18 volt panel!)


b) ALL solar arrays on boats will need a charge controller, that adjusts the panel / array output to the proper charging voltages...

{to be clear, ALL solar panels/arrays that output more than about 0.5% to 1% of your rated battery capacity, will need a "charge controller", that adjusts the panel/array voltage to proper charging voltages...
An example: a 100 A/H battery has about 1250 watt-hours capacity, so a small 10-watt, low-voltage panel, [36-cell ("18-volt")] can be directly connected (with a diode), without a charge controller, and you'll never over-charge, nor raise the battery voltage too high..
But, any decent-sized panel will need a controller!!}


c) MPPT controllers are what have been recommended now for almost the past 20 years!



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Also, if you're talking about a wind gen?
And, even adding a pole on the other side (port-side) for a wind-gen....why not just use this to mount more solar??
Quote:
Originally Posted by Na Mara View Post
Will 400W of solar plus maybe 400w of wind do it?
Quote:
Originally Posted by Na Mara View Post
....I can maybe fit 200 W of solar easily above my radome that can give me maybe 100Ah a day at a very low cost to generated Ah and close to zero nuisance to me.

......I could add a wind generator on the aft port quarter but am likely to be disappointed by its output and annoyed by its noise (having said that I was recently moored beside a six blades generator and I honestly could not hear it turning).
(I think you must've missed rule #1 of solar?)

Of course, as I wrote above, you really need to do an energy survey and write-up your energy budget first....but to be blunt, forget the wind gen!!

Oh, and as for not hearing the wind gen on the other boat....that's fine....but, you need to be aware that it was likely not producing any charging at all!! \
(yes, I know, it was spinning and looked like it was working.....but, unless it had about 10kts-11kts spinning it, it's doubtful it was doing any charging.....and even if it was, look at the specs of these things and you'll see you don't get much charging output until 15kts....and most of us avoid anchorages with that much wind...)


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Nu Mara, I was going to just make one last post here to hopefully help you out a bit more, by reiterating the accepted rules of solar! BUT...
Quote:
Originally Posted by Na Mara View Post
. We are five years out from the North Atlantic circuit.
But, two things have come up here that leads me away from that....and directs me to give you some better info....please read it and heed it...

--- One is that I now see that you haven't yet done an energy survey and written an energy budget {'cuz you haven't yet decided on what equipment / systems you'll have on-board....nor have you figured the increase in consumption of your existing systems, such as your refrigeration consumption in the tropics, etc.}


--- Another is that you now state that you are 5 years away from departing across the Atlantic? {I was under the impression that you were currently outfitting, before heading south, for this autumn's departure? Wow, did I get that wrong, huh? }


So...
So, please understand that the first thing you must do (and I thought you already had done?) is a complete / total energy survey and energy budget!!
This should be done prior to anything else, otherwise you'd just be taking a pot-shot approach to energy/solar/batteries, etc...



I cannot stress this enough, so allow me to repeat with emphasis:
The first thing you should do is a complete / total energy survey and write-up an energy budget!! This should be done prior to anything else, otherwise you'd just be taking a pot-shot approach to energy/solar/batteries, etc...



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fyi, in addition to my experience with solar, I've given seminars in alternative energy / solar / batteries, etc....

And while I know Li-type batteries are all the rage these days, I'm not a big fan...but I won't argue about them, 'cuz they do work....
(It's just that I'm not willing to buy/recommend something that:
a- costs more $$$;
b- doesn't seem to be easily serviced/replaced in any remote areas;
c- their BMS systems are prone to causing RFI;
d- don't have the long-term-history of reliability of lead-acid..)
So, I'm still in the Lead-Acid camp...especially because they are inexpensive, reliable, and easy-to-service or replace anywhere on earth...
~~~~~~~~~~~~~~~~~~~


Now, once you have decided on what equipment / systems you'll have on-board, and done a complete energy survey / budget....then, and only then, you can proceed fairly easy-peasy with solar, batteries, etc. selections/choices!

~~~~~

Forgive me for not just posting this the other day, but I assumed you were outfitting now before heading south and the across later this year, and that you'd already done your energy survey/budget, and were aware of most of this below....
Quote:
Originally Posted by Na Mara View Post
We are kitting up the boat for a North Atlantic circuit and I am now getting around to the electrical system.
But, with all the back-n-forth in this thread, I see this is not the case...

So...


Here are the generally-accepted on-board energy system rules (for most mid-sized, offshore sailing / cruising boats), that you apply AFTER you have done your energy survey / energy budget:


Rule #1) Your energy system is a "system", and should be designed as a "system" not piece-meal, nor in a pop-shot manner.....and this includes all energy generation; and all energy storage; and all energy consumption; all combined into a system design....(please see some of my other postings on how this is done, especially detailing how to reduce energy consumption underway)




Rule #2) Install as much unshaded solar as you can fit, and afford....
Addendum 2b) Use high-quality MPPT controllers.
Addendum 2c) Wire panels in parallel, and use adequate sized wiring.

Please read this Rule #2 again, with the key word in mind...Unshaded!

(and, please note the mirror image of this rule is also important to heed....do NOT install solar panels that will be shaded!!! This is a waste of time/effort and money!!!!)

I'm not sure how to drive this point home, without being rude....so, here goes...
Please stop thinking about "solar", and start thinking only about "Unshaded solar"!

Reading some of your continued posts here, you are discussing where / how to mount solar panels, wondering which ones would work / how well they'd work, as they'd be shaded....

So, I'm writing this in multiple colors and rambling on here about this VERY simple rule, to drive home this very important point.

You are wasting your time / effort thinking about "solar", when you should be thinking only about "unshaded solar"....
There really isn't a way that I can stress this more!


Please do yourself a favor and take this rule as an absolute!!!

Rule #2) Install as much unshaded solar as you can fit, and afford....

(and until you fill your unshaded solar space, do not start thinking about shaded solar....actually I'd like to just say "never" thinking about shaded solar, but doubt anyone will take me seriously...)



Rule #3) Re-read rules #1 and #2, and heed them...'cuz they apply to everyone, and are the two most important rules to follow!



Rule #4) Reduce energy consumption as best you can....
4a) improving refrigeration/freezer insulation....
4b) improving autopilot system and sail trim....
4c) use adequately large DC system wiring....
4d) accept that there is no need to run a chartplotter or computer 24/7 when at sea and design your sailing/navigation/energy system accordingly....
4e) And, while this is to help everyone else (by not cluttering up their AIS screens), not your energy consumption...unless you've anchored adjacent to busy shipping channel, please turn off your AIS transponder at anchor / in port!

4f) use LED anchor light and LED masthead tri-color or deck-mounted LED Nav lights....
4g) eliminate/reduce DC-AC inverter use....
4h) if you choose a watermaker, please consider a high-efficiency / low-power-consumption unit..



Rule #5) [please note that "batteries" are a whole discussion on their own, and there are many minute details and peculiarities of the various batteries, etc., that are well beyond this discussion...so, this is just a very brief overview....oh, and we are talking about real/true deep-cycle batteries here, not just ones advertised as "marine/RV", nor those as "dual-use", etc..]

Rule #5) Install adequate energy storage (batteries), that will generally allow you to do two things:

--- sail/cruise (and/or sit at anchor) overnight, without any charging during this 24-hours, and still have approx 2/3's of battery capacity left, before charging starts...(this is an "approximate" value, and varies widely depending on both owner's desire, battery types, and charging sources....so, this particular spec is a general guideline)

--- sail/cruise (and/or sit at anchor) for at least two days (preferably longer), without any charging / energy generation input to the batteries, and still not drain batteries beyond 50% capacity...


{note that while Li-type batteries are generally accepted to have long-life and adequate capacity even when drained down to 10% - 20% state-of-charge, meaning their "accepted capacity" for our calculations is 80% to 90% of their capacity ratings....assuming you are able to get them back to 100% state-of-charge everyday....

but, for Lead-Acid batteries (whether flooded, Gel, or AGM), it is generally accepted that in order to maintain long-life (lots of cycles) and adequate capacity, you shouldn't drain them beyond 40% - 50% state-of-charge....and since it takes significant time to get them charged-up the last 10%-15% (usually takes longer to get from 85% up to 95% state-of-charge, than to get from 50% up to 85% state-of-charge)....so, many with lead-acid batteries use a range of capacity starting at 90% state-of-charge...although those with large solar arrays can usually get them to 95%-100% regularly...

please remember that this is a list of rules and guidelines, not an absolute design template....as you need to do some of the work....especially you need to do your energy survey and draw up an energy budget!}



So, for lead-acid batteries (again, whether flooded, Gel or AGM) assume you can use about 25% of capacity daily (from 90%-95% down to 65%-70% = 25%)....that would mean that you'd want a main house bank capacity of approx 4 times your total daily A/H's used....

And, we can assume/approximate that two days use (without any charging) would get you down to approx. 40% - 50% state-of-charge....you're still good-to-go, with a main house bank capacity of approx 4 times your total daily A/H's used....but....but, be aware that draining most lead-acid below 50% reduces the longevity (life cycles) of the battery...with the lower-quality batteries suffering significant loss in life cycles....so, most will size their main house bank larger...

Most sailors that have the room on-board will size their main lead-acid house bank to be 5 times their daily A/H's used....some will even goes larger...

Obviously, typical lead-acid house bank sizes get larger as the boat get larger....and these days, this ranges from about 650 A/H's to 900 A/H's....




Rule #6) Use high-quality MPPT controllers, high-quality rigid panels as budget allows, use adequate support / brackets to handle full Gales or even Storm force winds.



Rule #7) Use water-generator (towed-water-generator) on long passages, to a higher priority than a wind gen...



Rule #8) Only install wind generators on boats that sail and anchor in very windy regions....most wind gens produce no usable output at wind speeds below 10kts, and most sailors prefer to anchor in protected areas with light winds....so, most find wind gens to be of little use these days....

Also, never install a wind gen where it will shade/shadow a solar panel....
{I have personally seem a boat 8 feet smaller than mine, with a 400+ watt solar array that was partially shaded by a ~ 350 watt wind gen....they complained that neither a good job, and said they guy selling them is a crook, etc....and they ran their main diesel everyday at anchor to keep up with their energy needs... I (and others) tried to suggest that they remove the wind gen and try just the solar and they just ignored the advice....and btw, I hear this story from others as well, and it can't be the same boat in every story, so this proves there are many that ignore this advice, to their own frustration}



There is more, but you've got to do some homework....and you've got 5 years...


I do hope this helps...and I do wish you well in your design / set-up, but remember you have many years to do this...and, I don't have the time to go thru this again, step-by-step....the basics are here for you, as are the rules....use 'em or not....your choice...



Fair winds

John

P.S. Please know that "batteries" are only slightly less controversial than "anchors"....
Just saying, ask 10 cruisers their thoughts on batteries, and you'll come away with 20 different opinions!!!




P.P.S. My last name is MacDougall....and my parents did a great deal of sailing around Scotland, including in front of the MacDougall castle, etc...the Heberdies, Orkneys, etc...


I'm a warm weather sailor....I sailed Portugal, Spain, Gibraltar, France, Morocco, Greece, Turkey, etc., a few seasons in the Med.....as well as across the Atlantic a few times, etc....(and, of course, all over the Bahamas and Caribbean), but the closest I ever got to Scotland was Heathrow Airport! Ha Ha....

Take care!
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