Could someone check my math please?

[ka4wja]

Nu Mara, et al,

1) Good news....I finally found the images I was looking for in a old docs folder!
(looking for docs or images using "solar" = no joy....but I labeled them Kyocera Shading Images, because they came from a old Kyocera tech sheet, from almost 20 years ago!)


Now, solar panel shading (especially on a boat!) is never exact / perfect...and that video I linked to, is good in showing this....

If you want to see what solar panel manufacturers show, in regards to performance when there is some shading....
Just one look at these images and you can easily see why/how panel shading is so detrimental to output!

Here is an image showing partial shading that reduce the solar panel output by 50%...(courtesy Kyocera Solar)
This shows 3 different ways of shading half of just one cell....half of some cells in a group....and half of some cells in a series string....and you see no matter which, this cuts the panel output by half!






Here is an image showing partial shading that reduce the solar panel output by 100%...effectively making the panel useless.....(courtesy Kyocera Solar)
Whether it is just one entire cell, or entire cells in a group, or entire cells in a string....or the whole darn panel....you'll get no power from the panel...





If you compare these images, with the parking-lot test in the video, you can easily see that the results are darn close / the same!

And, you can also see why a small rigging shadow from a shroud or stay, does not have the same result as shading the panel / significantly shading one cell, etc...

AND....

And, now maybe you can see why I've been saying for decades that it's not about how much solar you have, but rather it's all about unshaded solar!


2) Here again is the video I posted earlier....

https://www.youtube.com/watch?v=1qD3mN8VotQ

3) And, here is a link to a worksheet, use the first part for adding up your devices, in order to make an energy budget....and after you do that, there is more in this that you might find useful, or might not, in making battery / alternator choices, etc...(courtesy of West Marine....surprise to me, but that's one of the first things that came up in a Google search)

https://newcontent.westmarine.com/content/documents/pdfs/WestAdvisor/Elecbugt.pdf

Understand this worksheet is dated 1997....so, some things have changed since then....and this is geared more for the powerboater, but the first part (making your energy budget) applies to all boats / sailboats as well...


Use these tips, and you should find this worksheet useful:

a) Now, as I wrote earlier, I recommend a battery bank capacity of 4 to 5 times your daily usage (rather than their recommend of 3 times)....

b) And, I recommend adding up ALL devices (loads), and being generous with their usage hours and current draws, giving you a high daily usage number...

c) Ignore their "inverter load" part of the worksheet, especially if you have a 230vac boat (rather than the USA 120vac boat)...as I think you already mentioned not using inverters, but regardless inverter use should be kept to minimums, and rather using devices in their native voltages...

d) Until you have a better understanding of battery systems, and have determined what type of battery system you'll have, the part of the worksheet that helps you size your battery bank is premature...
And, in actuality here, it might just be moot....as most of ocean-going / offshore sailboats will just equip with the largest bank they can fit / afford (just like unshaded solar!)

e) Ignore the section about minimum time to recharge....as you'll be using mostly solar not alternators, and especially as you'll be drawing power at the same time as charging....




I do hope this helps everyone, and clarify things a bit...

Fair winds.

John

[ka4wja]

Nu Mara, et al,
After rereading my post from last night, I had a "duh" moment...thinking maybe nobody has ever showed you how to do the "energy budget" I was speaking of....
I mean the title of your thread here is "Could someone check my math please?", which (along with the words/numbers you wrote) indicates that you have tried to do it but, I started to wonder if anyone actually showed you?

So, yes, last night I posted a link to an energy survey/budget worksheet, and tips in using it....and, I do hope that will help...but...

But, I also thought maybe if I actually show you how you can do it quickly and pretty easy-peasy, you'll see what's what, and why it's so important...

So, while I'm quoting my post here from last night, I'm also adding below a quote from a posting of mine from just two months ago (in response to a comment from someone implying my Nav Station looked like it consumed a lot of power), showing my "back-of-the=napkin" Energy Budget...
Have a look, below....

Originally Posted by ka4wja

Nu Mara, et al,

1) Good news....I finally found the images I was looking for in a old docs folder!
(looking for docs or images using "solar" = no joy....but I labeled them Kyocera Shading Images, because they came from a old Kyocera tech sheet, from almost 20 years ago!)


Now, solar panel shading (especially on a boat!) is never exact / perfect...and that video I linked to, is good in showing this....

If you want to see what solar panel manufacturers show, in regards to performance when there is some shading....
Just one look at these images and you can easily see why/how panel shading is so detrimental to output!

Here is an image showing partial shading that reduce the solar panel output by 50%...(courtesy Kyocera Solar)
This shows 3 different ways of shading half of just one cell....half of some cells in a group....and half of some cells in a series string....and you see no matter which, this cuts the panel output by half!






Here is an image showing partial shading that reduce the solar panel output by 100%...effectively making the panel useless.....(courtesy Kyocera Solar)
Whether it is just one entire cell, or entire cells in a group, or entire cells in a string....or the whole darn panel....you'll get no power from the panel...





If you compare these images, with the parking-lot test in the video, you can easily see that the results are darn close / the same!

And, you can also see why a small rigging shadow from a shroud or stay, does not have the same result as shading the panel / significantly shading one cell, etc...

AND....

And, now maybe you can see why I've been saying for decades that it's not about how much solar you have, but rather it's all about unshaded solar!


2) Here again is the video I posted earlier....

3) And, here is a link to a worksheet, use the first part for adding up your devices, in order to make an energy budget....and after you do that, there is more in this that you might find useful, or might not, in making battery / alternator choices, etc...(courtesy of West Marine....surprise to me, but that's one of the first things that came up in a Google search)

https://newcontent.westmarine.com/content/documents/pdfs/WestAdvisor/Elecbugt.pdf

Understand this worksheet is dated 1997....so, some things have changed since then....and this is geared more for the powerboater, but the first part (making your energy budget) applies to all boats / sailboats as well...


Use these tips, and you should find this worksheet useful:

a) Now, as I wrote earlier, I recommend a battery bank capacity of 4 to 5 times your daily usage (rather than their recommend of 3 times)....

b) And, I recommend adding up ALL devices (loads), and being generous with their usage hours and current draws, giving you a high daily usage number...

c) Ignore their "inverter load" part of the worksheet, especially if you have a 230vac boat (rather than the USA 120vac boat)...as I think you already mentioned not using inverters, but regardless inverter use should be kept to minimums, and rather using devices in their native voltages...

d) Until you have a better understanding of battery systems, and have determined what type of battery system you'll have, the part of the worksheet that helps you size your battery bank is premature...
And, in actuality here, it might just be moot....as most of ocean-going / offshore sailboats will just equip with the largest bank they can fit / afford (just like unshaded solar!)

e) Ignore the section about minimum time to recharge....as you'll be using mostly solar not alternators, and especially as you'll be drawing power at the same time as charging....




I do hope this helps everyone, and clarify things a bit...

Fair winds.

John

Nu Mara, et al,

Here is the quote from a posting of mine, from two months ago....this is just a snippet of the post/thread.....
(Here is that whole thread / posting: https://www.cruisersforum.com/forums...ml#post3153960



This is specifically about my energy budget....and it's just a quick, "back-of-a-napkin" approach, but damned accurate...



This here (in the quote below) will show you how to do a quick energy budget / survey!!
And, shows you what that worksheet ( https://newcontent.westmarine.com/content/documents/pdfs/WestAdvisor/Elecbugt.pdf ) helps you do...

Also, be sure to click on those links to the articles/pics of Solar Panels Towed-Water-Generator
and Frig/Freezer , 'cuz they will take you to the articles detailing my specific design/install/use of them, on my current boat...

Originally Posted by ka4wja

<snip> ...
Solar Panels

Towed-Water-Generator

Frig/Freezer

<snip>

I'm going to be generous here, showing higher consumption than I personally use...(but perhaps more accurately represents the "typical / normal" mid-sized cruising boat?)


a) In tropical climes (such as summertime Florida, Bahamas, Caribbean...and sometimes even summertime Med), typically the single largest power consumer on-board most cruising boats is their refrigeration / freezer...and this is the case for me, where my frig and freezer consume 60 - 80 A/H's per day (sometimes as much as 90 A/H's per day, keeping ice cream frozen in July), depending on ambient temps and how full the boxes are...and this is with 0* to +5*F freezer temps, and 34* to 38*F frig temps.....which are attained all-year-long...(fyi, colder is attainable, but with higher power consumption and/or the use of countertop insulation boards)

Let's use ~ 70 to 75 A/H's per day, for sake of this discussion....but probably less, in almost all circumstances...



b) And, typically the second largest power consumer (while underway) is the autopilot (fyi, sail trim and helm balance is important here)...and again this is the case for me, where I see about 45 - 75 A/H's per day when sailing offshore, typically 45 - 60 A/H's per day, but in heavy following seas it can be as high as 75 A/H's per day....

Let's just use a round number of ~ 60 A/H's per day....



c) Although large screens (chartplotters/radar) are also relatively high power consumers, these are not typically run all that often (at least not by me!) and when running a large screen chartplotter and/or radar, many sailors (at least me, and many sailors I know) are typically underway approaching a coastline (where engine power might be used more often, as fuel is typically available nearby) and/or under engine power (such as if in fog)....but, if you take an approx 1.5 to 1.75 amps for a full-sunlight-visible 8" chartplotter, and 2 to 2.5 amps for a larger 12" to 14" full-sunlight-visible chartplotter, and another 1 amp for a radar scanner....equaling about 5 amps overall....and maybe an hour or two of use per day, means 5 to 10 A/H's per day (but, maybe no consumption at all, except for when using engine?)

So, just to say we will use these some, let's assume about 5 to 10 A/H's per day...and sailing the Caribbean as the original poster will be doing, he might not use them at all....(but, if you were in bad weather, along a coast, looking for T-storms, needed radar, etc, and you ran one of these 24/7, figure about 40 - 50 a/h per day, including radar...)



d) 24/7 receiving of VHF-DSC-FM = ~ 25 A/H's per day

24/7 GPS unit with basic display/navigator = ~ 1.5 A/H's per day

24/7 secondary GPS (for DSC radios) = ~ 1 A/H per day

24/7 AIS transponder (with its own GPS) and Watchmate display = ~ 10 to 11 A/H's per day

24/7 Depth sounder, Speed Log, and Wind transducer (all with basic displays) = ~ 5 to 8 A/H's per day

12 hrs use of LED Nav Lights = ~ 1.5 A/H's per day

1 to 2 hrs of SSB radio use per day = ~ 2 to 6 A/H's per day

1 to 2 hours of WeFax reception per day = ~ 2 to 4 A/H's per day


This section adds up to 48 to 58 A/H's per day....so, let's just round-it-off to an even ~ 50 A/H's per day...


e) Cabin lights (LED's), Cabin Fans (Hella Turbo), domestic water pressure pump, stereo, etc....except for some cabin fans, none are run 24/7...and, while exact consumption of all of these varies depending on a particular sailor's lifestyle, etc....we can assume an average of about 5 to 10 A/H's per day, from all of these combined....

Let's just say ~ 5 A/H's per day...



f) Spectra watermaker....about 8amps to make 7.2 to 7.5 gals...run for 4 hours or so, every 3 to 5 days, which equates to approx. 6 to 10 A/H's per day, on average...

Let's just say ~ 10 A/H's per day...


If you add up all of these numbers, you get ~ 200 to 210 A/H's per day, when underway and offshore...and about 1/2 of this (50% to 60%), approx ~ 120 - 130 A/H's per day, when at anchor, where no autopilot, chartplotter/radar, AIS, etc. is needed, nor is 24/7 use of VHF, etc....but more use / more consumption from lights, fans, stereo, watermaker, radio, etc...




An actual real rule-of-thumb, of solar arrays charging 12vdc battery banks, is:
In low to mid latitudes (areas with decent sun angles), or high latitudes in summertime (where there are longer days of sun), as long as your solar array isn't shaded (and has adequate airflow around panels, especially under the panels), and you use MPPT controllers, you can get 40% or so of your panels' wattage in actual A/H's per day (at 14vdc)...and if sun angles are good (and batteries can accept the charge current), you can approach 50%...BUT...

But, shade is the enemy here....even small amounts of shade will reduce your array output....now, small intermittent "shadows" (like from a rigging wire) are typically inconsequential, but "shade" is very bad...

{Fyi, although I was playing with solar in the 1970's, I did my first commercial / off-grid solar array install in 1984....and played with solar on-board some boats around that time as well....and in the early 1990's did some solar installs on boats....so, in addition to my experience with electronics, I've been dealing with solar for decades.... }


As, yes, I do have a rather extensive suite of on-board marine electronics and communications gear (not seen in most of those pics, are my Bullet wi-fi system, Iridium 9555 phone, back-up VHF-DSC-FM, back-up MF/HF-DSC-SSB, multiple handheld VHF's, portable SW rec,, additional handheld GPS's, etc. etc....none of which use any electrical power, 'cuz they are stowed securely unless needed), but everything is all run easy-peasy off 12vdc house batteries charged by alternative energy (mostly solar), and has worked well for me for years and many 1000's of miles of cruising, including a few Atlantic crossings, etc...

Fair winds.

John

I do hope this help....really!

Fair wind

John

[sailinglegend]

We all appreciate you knowledgable postings but please be careful repeating unsupported MYTHS.


[QUOTE=ka4wja;3201613]

Please understand:

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

This is correct

{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!!}

This is totally incorrect!

It's not the output power but the output voltage that the panel will produce when the battery is 100% fully charged. If you leave the boat - with no loads on the battery - then the voltage will quickly rise to over 15 volts and boil the batteries dry.

Please see MaineSail's video which clearly shows the problem - also others on youtube:

https://www.youtube.com/watch?v=z5RtZe9AW2E

[ka4wja]

Sailinglegend,
Yes, I'm aware it is the voltage...
You and Mainesail are of course correct!
Thank you for reminding me be more circumspect!

I shouldn't have tried to caveat my words...I should've just kept things as an absolute...or done a better job of proof-reading!

BUT...

But, I was not speaking of unattended charging, without any loads on the battery bank....but, of course rather was writing about charging when using the batteries!!

And, as you can see in that video (at 4min 26secs in) that he does mention this....


Again, I probably just should've left it at an absolute...all panels will require a charge controller....but, in the context of what I was writing about, it's not always an absolute...

Thank you for pointing this out!

fair winds

John


P.S. back in the really old days, we used Ford "voltage regulators", which just connected the panel to the battery at a certain voltage and cut-it off at a higher voltage (14.2, I think)....but that was about 40 years ago....and, we never overcharged anything, but of course we didn't charge things that well, either.... LOL

[Na Mara]

Re.ka4wja

Thank you for taking the time to find and share your older posts in this topic. I have tried to do an energy budget and I have to say that mine came out almost exactly the same as yours after I took into account the greater consumption of refrigeration in the topics. Mine are a little lower than yours but that is because I do not have a freezer and I don’t run quite so many electronic devices. However, my autopilot uses a bit more than you budget for so it more or less evens out. Basically, I can’t be that far out even using your own math.

I will be getting a sophisticated battery monitor fitted this year along with one unshaded solar panel above the radome and some kind of hydrogenerator then I will be able to tell you exactly how many amphours I’m burning through.

If my consumption is around 200Ah and I size the bank so that it’s 5 times the worst case consumption then I need 1000Ah. I can fit 900Ah relatively easily but 600 is easier still and that is 6 times my at anchor usage.

Today I was out sailing in a force 2-3 with a reef in both white sails taking it really easily for the family and Na Mara was still making 5.5-6.5 knots on all points of sail. Im going to be able to meet my needs underway with a hydro generator. That being the case its my at anchor requirements that should determine battery bank size presumably? In which case 600Ah is more than enough.

Watt and sea are now suggesting a pod 600 just aft of the rudder under the transom. If that works it’s a neat solution as it gives ease of access for getting weed off it (it’s also unlikely to get any on it directly aft the rudder), it puts the holes in the hull above the resting waterline, and it gets the unit on the centerline. I just worry that the turbulence of the rudder will negatively effect the generator and it might not be operating at the ideal depth. Any of you heard the like before?

[ka4wja]

Nu Mara, et al,

A couple brief things...


1) Please remember that all boats are different and that all sailors are different....and what "fits" in one boat, might not fit in another....and/or what one sailor might wish to "fit" in one location, another sailor might have a different use for that space...

So, while you can take the advice of others, hopefully only from those learned / experienced....please remember to make your decisions based on your boat, your needs/desires, and your application!

So, if you can fit 900 A/H's of batteries that's great....but, if not, no worries...




2) Unshaded solar! Go for it!!

And, as for shade....in that vein of advice that you can ignore or take....until you've spent time on-board with the tropical sun beating down on you, on your cockpit and cabins, etc. (and of course the overall heat and humidity of the tropics), you might not realize how important some shade is going to be, shade for you, your family, your cockpit, your cabins, your boat....shade for everything but the solar panels!

{Btw, although bimini canvas and/or some form of shade, is de rigueur in tropical cruising grounds....there are somethings you all up north might find just plain odd, but I'm not the only sailor who has used beach towels and/or bed sheets tied to the bimini (or use clothes pins), or the boom, or standing rigging, etc., to provide some additional shade!!


And, fyi, when in Caribbean, etc., where the easterly trade winds blow, you'll find that having a couple solar panels out aft (such as over the cockpit, and/or the transom area) can provide some nice later afternoon shade....and hanging some towels or a sheet from the panels (although looking much tackier than a nicely made canvas or screen shade) can actually be a nice way to dry off your towels after a late swim AND give you some late day shade for relaxing in the cockpit...}





3) Energy budgets...

Well, looking at mine, yep it might seem high....but I've got a 47' sloop, and a big frig and freezer....and, in reality, my "at anchor" energy budget is actually low compared to many boat of the same size...

Also, remember that the above info was an example, not precisely exactly what I do / use....


Case-in-point....the 5 - 10 A/H's per day of radar/chartplotter use I mentioned, is actually almost 0 / Zero for me, offshore....as radar is only needed in poor visibility situations (rare in the type of ocean sailing I do, except when approaching a coast), and when looking to find the weaker areas of T-storm cells, etc. (I actually used MARPA a couple times, to see how well I could track, and plot thru, some storm cells)


So, except for that, the AIS transponder, and some yacking away on the HF radio (and the second GPS), which collectively add up to about 20 - 25 A/H's per day...my marine electronics energy budget isn't that high....


At sea, everyone is going to have their VHF on 24/7, most will also run a GPS and some instruments, and everyone is going to have nighttime use of Nav lights, yes?


So, as you see, it's frig/freezer and autopilot that are the two biggies here....





4) As for a permanently mounted water-generator?

Well, not for me....but as I said up above in #1, it's your boat and your decision.





Wishing you good luck....and fair winds.


John

[Haddock1]

I did the attached spreadsheet whilst basic might be of interest/help.

[jalmberg]

We went the other way: slashing our requirements. We use about 60 amp hours day. We have a fridge, all led lighting, 3 good fans, a small chart plotter, AIS, radar (only when needed for fog, etc.), phones, SSB, instruments... everything you need for offshore sailing. We have an Aries windvane, which consumes no power. 2 100 watt panels supply 90% of our energy, and we fitted a modern 3-stage alternator to the engine for topping up and for those inevitable rainy weeks, but running the engine for electricity is a real drag, so we try to avoid the need. Minimize! You don’t need all that electronic junk at sea. Plus, you never know when it will all quit on you. We could continue to sail and navigate with zero electricity if we had to. A significant safety margin, IMHO.

[IanTrail]

Wow, we all have hugely different experiences: I guess different boats, different lifestyles and different cruising grounds. All I can do is add my experiences:
My wife and I did the Atlantic circuit (UK to Caribbean and back) in our 46 foot monohull. We are now in the Med but the pattern is the same.
We have a 50 watt solar panel, Aerogen 6 (big) wind generator and 140A second alternator with intelligent charger. Batteries are 420AH AGM.
General conclusions:
Forget a 50 watt solar panel for charging. It's good for keeping the battery topped and the intruder alarm going when the boat is left for weeks unused but the output is negligible. However, I have met guys with catamarans covered in panels who do get useful output - but you need a lot.
Similarly, the wind generator needs 15-20 knots before it really starts doing anything; even in the Caribbean 10-15 knots is more usual. Of course, you get more amps up-wind than down-wind.
I hate to say, as a sailor, that there is no substitute for burning diesel! Our normal daily routine, whether sailing or at anchor was to run the engine for an hour or so each day. We would run the watermaker for a couple of hours then start the engine with the watermaker still running. The 140A alternator was well able to re-charge the batteries from 80% to 100% in this time. The engine also heated our hot water and our engine-driven fridge compressor pulled down the fridge hold-over plate. So after an hour or so, job done: batteries 100%, water tanks full, loads of hot water and a nice cold fridge. All set for another 24 hours.

[Na Mara]

Re Iantrail,

That is very valuable experience but also quite depressing. Prior to your comment I was going to go for a 90W victron solar panel over my radome (unshaded) and a further 240 W of sunbeam tough x panels on my pilothouse roof (about 120 W or more of which should be unshaded at any particular time.) with a duo gen 3 serving as wind generator at anchor and hydro generator underway. Now your power requirements seem larger than mine but even still, you seem to be saying that I am unlikely to meet my needs with this set up.

I just found out today that there is no space in front of my engine for mounting a second alternator, so I would have to replace the existing one.

All this is just making me think that I should bite the bullet and buy a fuel cell. I know their lifespan is about a year or so of heavy use, that they are expensive and that the fuel requires care and is also expensive, but quite honestly it seems to be the only way of meeting my needs. I would have the panel over the radome to keep the batteries topped up when we are off the boat, a hydro generator to cover our needs underway, and a fuel cell to avoid running the engine otherwise.

I hate the engine. As a sailor I see the thing as necessary evil for getting me into and out of port and out of sticky situations. Also for minimising maintenance needs I just want to run it as little as possible. Maybe that is silly, but damn it, its the way I feel. Anyway, a high power alternator with external regulator fitted and wired in is going to set me back 2000 plus euros and last maybe 5 -10 years. An EFOY fuel cell run maybe 40 hrs a week will set me back 5000 euros fitted and finished and last 2-3 years. All the extra fuel and engine wear running the engine for electrical generation probably about equals the cost of the methanol for the EFOY. So yes it is more expensive, but its not going to kill me.

[waterman46]

Na Mara, you say you have room for at least a small diesel genset but you seem very biased against it, such that as alternative you are considering exotic and expensive sources like a fuel cell. In my experience, a genset is the best power source for long periods at anchor where there is little solar for days on end (you plan to cruise in northern climes).

You are right that running a main engine for electrical power generation is not a great solution. You would find that a well installed and sound insulated diesel generator will be your best power friend at anchor. Not cheap, but neither are the power pods or fuel cells and the genset will last longer. If a fuel cell or pod fails, you cannot fix it and neither can anyone but the factory. A genset will last 20 years or more and can be repaired by yourself or a mechanic almost anywhere in the world. It can provide instant power anytime needed, including under sail to feed the autopilot needs.

[Na Mara]

Re a genset.

I do like that option slightly more than the alternator option.

Yes I have space for a small one next to the engine in the insulated engine bay with good access.

I do like the longevity, the ease of repair, and the fact I get hot water for free.

Here is my thought process on this one.

1 it’s a very expensive installation at 10000+ euros and upwards (that’s 6-10 years of Efoys), though if maintained it can last decades.

2 Na Mara only carries 350 liters of diesel and a beta 7 genset uses about 1.5 l/h at half load. Now these bad boys can kick out a whopping 600A so I wouldn’t need to run the thing for more than half an hour a day or an hour every second day but even still, that’s about 6 liters a week. Actually, that’s not that much when you come to think about it. It would probably only have a marginal effect on my diesel autonomy. I calculated that we carry about three months worth of diesel. Adding a genset would only reduce that by a week or two. Maybe consumption goes in the plus column on this one.

3 Not very eco friendly ( but a damn site better than running the engine for electricity) and maybe they will get around to making synthetic/bio diesel one day. The methanol for the EFOY almost certainly is from steam reformed natural gas but can be more easily made from renewables. Either way it’s substantially more eco friendly.

4 A genset is another thing that has to be maintained. The way I understand the EFOYs is that you use them, with a periodic flush out, until the output drops below acceptable levels and then you send your existing unit back and plug in a new one. Expensive, yes but also very easy and merely relies on access to a post office. A genset is an additional ICE that requires all the same maintenance and care that the original one does.

5. The fuel is readily available, but I can carry a year’s supply of methanol for the fuel cell so not that big an advantage here.

6 An hour of noise and diesel fumes every other day isn’t too bad and it would be mounted in a well insulated engine bay but the EFOY is whisper quiet with no fumes.

7 the genset needs more active management, though the feul cell does need you to monitor and change the fuel cartridges.

8 the genset is much heavier. That being said, my engine bay is right over the keel so this is weight in the right place. I would have to add weight to port though to offset the weight of the unit as it would be about 70 cm off the centerline to starboard. All in all we are talking 3-400 kg of extra weight. That’s a good 3-4% of our lightship displacement. Ok it’s in the right place and will add to stability, but that’s a hell of a lot of extra kilos to be carrying. Even carrying a years supply of methanol the EFOY doesn’t weigh half that.

9 the gender has much higher output and would heat our water. But we don’t need such a high output unless we want AC, water makers, freezers or electric cooking which we don’t.

So all in all, while there are things going for a diesel genset, its weight, eco credentials, and initial cost make the Feul cell option easier to stomach. Basically a genset is more powerful than what we need so all it’s negatives aren’t outweighed by it’s higher output for us.

Best from Na Mara

[IanTrail]

Sorry Na Mara, I didn't mean to depress you. It sounds as though the set-up you plan will have quite a lot of capacity. I think my key points are (1) the manufacturer's claims for all these gizmos are always best case and (2) you do need the flexibility; some days are solar panel days, some are windgen days are some are engine days. Lots of everything is ideal!
I don't think that we are particularly power-hungry. Typically we get down to 85% of our 420AH daily. That's 63AH of which maybe half is the watermaker. All our lights, in and out, are LED so the remainder is just odds and sods. A couple of laptops for a few hours could easily be 30AH.
Here's a thought for when you mount your solar panels: I was in a marine electrical store in the Caribbean when a guy was buying a solar panel. The salesman told him "make sure you tilt it to starboard". We all looked at him confused so he explained: "In the Caribbean you are at anchor most of the time. The wind is usually E or NE, there are no tidal streams, so the boat is pointing E or NE. So the sun, to the south, is always on the starboard side of the boat". I'm still not sure whether this was a wind-up!

[sailinglegend]

Sorry for delay in responding - no internet!!!

[QUOTE=Na Mara;3201545]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!!!

Batteries should never be installed in an engine compartment if they can’t be topped up with water - this is fatal for sealed batteries. Floaded Lead Acid (FLA) batteries will need topping up, but battery life is halved for every 10° C rise in temperature above 25C.

At 25ºC batteries start to gas at 14.4v, at 40ºC they gas at 14v so an external regulator with a battery temperature sensor is needed to reduce the charging voltage automatically to compensate for this.


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).

Your AGMs were probably killed because they were in the engine compartment - but remember not all AGMs are created equal - only buy the best, forget the rest. Many are just designed for standby Solar or Telecom usage and not designed for daily high discharge, or for repeatedly falling off 3 metre waves.


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?

About two years before you set off you should have everything you need fitted so you can get used to the new kit - so hold back on AGMs - unless new batteries are needed now.

Originally Posted by Na Mara

....All this is just making me think that I should bite the bullet and buy a fuel cell. I know their lifespan is about a year or so of heavy use, that they are expensive

An EFOY fuel cell run maybe 40 hrs a week will set me back 5000 euros fitted and finished and last 2-3 years.

I've looked at Efoy very carefully and have had long discussions with them. They told me their cells are designed with an estimated lifetime of up to 10 years assuming average use of only 300 to 500 charging hours per year.

The cells run on Methanol fuel, but Efoy say their own expensive “ultra pure” fuel must be used, not commercially available Methenol. There are many fuel dealers in Europe, but few in the US. Transport costs will be very high if the fuel is not available locally because of the hazardous nature of Methanol.

For heavy users Efoy say at 5000hrs the unit needs replacing because the power output reduces to about 50% - that's only 4.4 amps - doubling the cost of the Methanol fuel at this stage. A replacement of the defective component will cost many £1000's + return costs to Efoy in Germany, but after this repair it is not a new unit. Therefore Efoy recommend replacing the whole unit after reaching the fuel cell's lifetime.

A 10 litres cartridge of Efoy Methanol produces 925 Ah

Effoy’s largest fuel cell gives 210Ah/day, that’s only 8.8 amps of charging current, so on a boat that needs an extra 150Ah/day the largest of their fuel cells would have to be on for 17 hrs a day, that’s about 300 days before it is at the end of it’s life.

Efoy do agree with me that for full time cruisers their fuel cell is not a cheap option.

[Statistical]

Originally Posted by Na Mara

Re Iantrail,

That is very valuable experience but also quite depressing. Prior to your comment I was going to go for a 90W victron solar panel over my radome (unshaded) and a further 240 W of sunbeam tough x panels on my pilothouse roof (about 120 W or more of which should be unshaded at any particular time.) with a duo gen 3 serving as wind generator at anchor and hydro generator underway. Now your power requirements seem larger than mine but even still, you seem to be saying that I am unlikely to meet my needs with this set up.

I just found out today that there is no space in front of my engine for mounting a second alternator, so I would have to replace the existing one.

All this is just making me think that I should bite the bullet and buy a fuel cell. I know their lifespan is about a year or so of heavy use, that they are expensive and that the fuel requires care and is also expensive, but quite honestly it seems to be the only way of meeting my needs. I would have the panel over the radome to keep the batteries topped up when we are off the boat, a hydro generator to cover our needs underway, and a fuel cell to avoid running the engine otherwise.

I hate the engine. As a sailor I see the thing as necessary evil for getting me into and out of port and out of sticky situations. Also for minimising maintenance needs I just want to run it as little as possible. Maybe that is silly, but damn it, its the way I feel. Anyway, a high power alternator with external regulator fitted and wired in is going to set me back 2000 plus euros and last maybe 5 -10 years. An EFOY fuel cell run maybe 40 hrs a week will set me back 5000 euros fitted and finished and last 2-3 years. All the extra fuel and engine wear running the engine for electrical generation probably about equals the cost of the methanol for the EFOY. So yes it is more expensive, but its not going to kill me.

A fuel cell? If you have the budget, space, and weight to carry a fuel cell you can just use a generator.

I really doubt think you even need that. A good amount of solar and an upgraded alternator should cover your energy needs. The more solar you can fit the easier the energy budget becomes.