A question probably asked, so pardon me if I repeat it.

[john61ct]

Originally Posted by mitiempo

40 amps for 20 hours from a 800AH bank is impossible.

I was only explaining the test-lab meaning of the 20-hour capacity rating there, nothing to do with any specific loads IRL.

I was perfectly clear about the folly of aircon-level loads off battery storage immediately thereafter.


> Do that a few times and you can throw the batteries away.

No, under strictly controlled conditions, 8-12 times over their lifetime will do little harm, especially since in that type of environment the bank is otherwise being meticulously cared for.

> The 150 amp example is also incorrect. Because of Peukert 150 amp draw would likely last less than 2 hours to 50% SOC. When you pull that high a percentage of capacity the bank size effectively decreases to a fraction of its 20 hour capacity

Which I also thought I expressed perfectly clearly.

[GrowleyMonster]

To go all out full bore solar, some compromises must be made. Maybe A/C only for your vee berth at night, for instance. Make water only on shore power. Diesel or kerosene burner for much of the cooking. And yes, there is room for more batteries. I have 8 golf cart batteries in my little boat. Did have 10, but decided I don't need a 12v house bank, so now everything sucks out of the 48v bank. And I am fixing to add a second set, 8 more golf cart batts. You don't have room? Make room. That's if you want more storage, anyway.



On a monohull your solar array quickly outgrows the boat if you want all the goodies. Sure, you can have more solar hanging out over the stern, or outboard to either side, but that can be a problem at sea or obviously if you are sailing her hard. So there is a practical limit, until someone makes a practical solar sail.


BUT... what you CAN do is use solar to provide only the more basic anemities, or just use it to reduce your fuel consumption rather than eliminate it. It doesn't have to be just one or the other. Maybe you run your generator an hour a day instead of 2 or 3 hours. Whatever. Save fuel, enjoy more peace and quiet, extend time between trips to the fuel dock. Whatever your priorities are.


Solar isn't a magic thing and you are only going to get so much out of what you can crowd onto your boat. Your expectations have to be realistic.

[LoudMusic]

Originally Posted by john61ct

Still not enough in the tropics.

Unless **very** well insulated

Yeah this Orana 44 isn't that well insulated, I'm discovering. But the master cabin HVAC seems to only draw about 10A on 120vAC, so probably 110A on 12vDC through an inverter? I haven't researched actual efficiencies for my hardware yet.

I have no intention of being in the tropics during the hot months, so likely it wouldn't run 24/7 anyway. Set it to maybe 80 during the day and 76 at night and partition off the bunk area from the rest of the hull so it's dealing with a much smaller volume of air.

That's a couple years away at best for us - still acclimating to boat life up on the east coast.

[mitiempo]

Originally Posted by john61ct

I was only explaining the test-lab meaning of the 20-hour capacity rating there, nothing to do with any specific loads IRL.

I was perfectly clear about the folly of aircon-level loads off battery storage immediately thereafter.


> Do that a few times and you can throw the batteries away.

No, under strictly controlled conditions, 8-12 times over their lifetime will do little harm, especially since in that type of environment the bank is otherwise being meticulously cared for.

> The 150 amp example is also incorrect. Because of Peukert 150 amp draw would likely last less than 2 hours to 50% SOC. When you pull that high a percentage of capacity the bank size effectively decreases to a fraction of its 20 hour capacity

Which I also thought I expressed perfectly clearly.

It was Jammer's post I was replying to.

Hope the op understands.

[wallythacker]

Originally Posted by SV Bacchus

Go to YouTube, search for "Gone with the Wynns" and see what they did. They dumped all propane and have a full electric kitchen, run their A/C units off batteries as well as watermaker.

It cost them a bunch but what a nice setup.

My boat should handle 4 solar panels on the arch over the transom, add another 6 flexible panels on my bimini, then add another another 4 on the cabin roof for a total of 14 panels without looking like a utility pole. If each panel is 150 watts that is 2100 watts of energy, then add another 800 from the two wind generators for a total power plant production of 2900 watts.

I do realize asking for 16.5kbtu of AC is HUGE. The advice given to run just one unit, the 5kbtu one and duct the cool around where needed is good advice. It has me thinking of how to install flappers on my air system so I have complete control of where the cold air flows. I don't think anyone has gone that far yet, perhaps I'm wrong and someone has a way to micro manage their AC.

Originally Posted by john61ct

Noise / vibration of wind genny drives me nuts personally.

OP are you inspired by environmental motivations to avoid fossil fuel power generation, or cost, or what?

I'm primarily motivated to see if everything the boat has can be utilized, more or less on demand, when away from the dock......without using the generator. So truly being off the grid when off the grid.

[jt11791]

Originally Posted by wallythacker

My boat should handle 4 solar panels on the arch over the transom, add another 6 flexible panels on my bimini, then add another another 4 on the cabin roof for a total of 14 panels without looking like a utility pole. If each panel is 150 watts that is 2100 watts of energy, then add another 800 from the two wind generators for a total power plant production of 2900 watts.

Those 400W wind generators only make 400W in a gale. I have one. In a 15kt breeze you will see around 5A@13V, or about 65W.


I don't know solar panels well enough to see your error, but 1000W is considered huge solar in the cruising boat world. If it were reasonable to install 2000W, lots of boats would have that, and they don't.


Another thing to remember is that some of your panels will be shaded by the boom, mast, and other rigging. This decreases your available power significantly.

[CatNewBee]

Originally Posted by jt11791

Those 400W wind generators only make 400W in a gale. I have one. In a 15kt breeze you will see around 5A@13V, or about 65W.


I don't know solar panels well enough to see your error, but 1000W is considered huge solar in the cruising boat world. If it were reasonable to install 2000W, lots of boats would have that, and they don't.


Another thing to remember is that some of your panels will be shaded by the boom, mast, and other rigging. This decreases your available power significantly.

To give some realistic figures on solar.

I have 5 high efficiency panels on my cat, nominal 1650Wp, peak output is around 1100W in the afternoon, daily harvest peak was 8500Wh at optimal condutions, 7500..8000Wh on average sunny days in the Med during last 2 months.

So I can calculate with 8kWh daily as maximum possible output, realistic is around 7.5kWh.
That translates to 560Ah daily harvest with LFP 12V (13.4V actualy).

But this energy is not excess, there are systems running 24/7, that consume a significant part of it. Anyway, running 1 A/C for 2 hours to cool down the berth in the evening is possible, the solar array can recharge this the next day.

The battery is not discharged that deep of course, because a big part of the incomming 560Ah are used straight into the appliances (fridges, freezer, water heater, galley) during the day.

Btw, you can save up to 120Ah per day, simply by not running the inverter all the time, but just turning it on when really needed.

[valhalla360]

Originally Posted by wallythacker

My boat should handle 4 solar panels on the arch over the transom, add another 6 flexible panels on my bimini, then add another another 4 on the cabin roof for a total of 14 panels without looking like a utility pole. If each panel is 150 watts that is 2100 watts of energy, then add another 800 from the two wind generators for a total power plant production of 2900 watts.

I do realize asking for 16.5kbtu of AC is HUGE. The advice given to run just one unit, the 5kbtu one and duct the cool around where needed is good advice. It has me thinking of how to install flappers on my air system so I have complete control of where the cold air flows. I don't think anyone has gone that far yet, perhaps I'm wrong and someone has a way to micro manage their AC.

I'm primarily motivated to see if everything the boat has can be utilized, more or less on demand, when away from the dock......without using the generator. So truly being off the grid when off the grid.

Are you scrapping the mast and rigging? On most boats, you see the panels hanging off the stern to minimize shading which even a small amount absolutely kills output...so your 2100w of panel might generate less than 1000w in reality.

Also 800w of wind implies a heck of a storm blowing thru..and if they are mounted on the stern, you have to factor in some more shading.

[valhalla360]

Originally Posted by wallythacker

So my 4x200ah AGM bank (all 12v batteries for ease of math) which provide 400a@12v for 20hrs (mfg. rating) will provide 50a@12vdc for about 8 hrs?

I read that half the rated capacity should be used for calculations.

My 5600btu AC requires about 5a@120vac or 50a@12vdc. Will I get about the 8 hours that I calculate the bank can provide? How much loss is there converting my DC bank to AC in the inverter?

Am I anywhere remotely close with my calculations or off by miles?

As for charging the bank back up i have room on my boat for 12 standard size solar panels without resorting to hinging them on the rails. Figuring on charging the bank up will come later.

To get 8hr,you need around 400amp-hr of usable storage. For lead acid batteries you can usually only use around 30-50% of the rated amount...50% is even a little optimistic as getting to 100% full is tough as they near full, the batteries accept reduced amps, so unless it's the stray night away from shore power, you probably need to jump up to a 1000amp-hr battery bank...oh and don't count on 100% efficiency, so maybe 1100-1200amp-hr.

To generate 400amp-hr (4800w-hr at 12v), you are going to need around 1200w of panels. Those panels need to be clear of shading and this only supplies the air/con. If you want to run water maker, fridge, etc...you have to estimate their demand and factor that in. That must be a pretty big boat if you can hang 12-150w panels off the stern.

Everything but the air/con if very possible without the system getting silly but while technically possible, running air/con is impractical.

[CatNewBee]

Originally Posted by valhalla360

Are you scrapping the mast and rigging? On most boats, you see the panels hanging off the stern to minimize shading which even a small amount absolutely kills output...so your 2100w of panel might generate less than 1000w in reality.

Also 800w of wind implies a heck of a storm blowing thru..and if they are mounted on the stern, you have to factor in some more shading.

One or two of them are very often shaded, but anyway, the figures are based on the victron MPPT monitor / history. It helps to clean the panels from time to time...

[GrowleyMonster]

I might also add that if you are going with AC from an inverter, rather than powering big high current loads with 12VDC, you may as well go with a 48v bank. Less current. Lower line losses. Still in the "nonlethal voltage" wiring standards. The increased efficiency will somewhat make up for the inverter. Modern sine wave inverters are quite efficient, typically around 95% or so as I understand. The ability to easily run ordinary household appliances has some value.



Anything over 50v is considered "lethal voltage" and there is a different set of electrical standards that you would need to follow. Also there are a lot of inverters, chargers, and DC/DC converters for 48v but not so many for higher voltages, which is a shame. Around 120v worth of golf cart batteries would be a pretty awesome bank, around 27kwhr, without having to wire in parallel or use expensive ultra high capacity cells. That would still be way less than a ton of batteries, and they can be had for $85 each or even less. With such a bank, you would find yourself limited by ability to charge them, rather than storage capacity.


If you could severely limit use of air conditioning, or eliminate it altogether on the water, you would find doing this to be a lot easier.


Another case for a higher voltage bank... backuup propulsion. A pulley on your prop shaft next to a pillow block bearing for stabilization, driven by a belt from a large brushless motor, and you could use your gigantic bank to limp back to the dock. Or maneuver in near silence. Or have instant on, propulsion on demand for "power tacking" or other maneuvering needs. 48v is ideal for boats under about 35 feet, 96v or higher if you go over 40 feet, typically.

[Sawbonz]

I just heard from the person who installed a 16k btu Frigomar A/C on La Vagabond that it is so efficient that it runs off of their 2000w inverter and their 320Ah AGM batteries lasted over night.

I am planning on 4 A/C units, 4K/4K/7k/16k and ample inverter power with a catamaran roof full of solar and a generator for rapid fill up of the LiFePO4 batteries.

BTW, John61ct I don’t think that the Wynns got “hundreds of thousands “ of dollars in free stuff. Maybe $30-50k, if that...

[wallythacker]

Originally Posted by valhalla360

That must be a pretty big boat if you can hang 12-150w panels off the stern.

Everything but the air/con if very possible without the system getting silly but while technically possible, running air/con is impractical.

No, I'm not hanging a dozen off the back, 4 or 5 like the picture shown and 6 flexible on the bimini and my cabin roof can handle 4 more.

14 panels @150w = 2100 potential watts.

It shouldn't be too hard to engineer something that disconnects the AC when another large load goes online like the watermaker. The AC can come back online when the watermaker shuts down.

I'm beginning to think there's a lot of room for better power management on boats. The power plants have evolved quickly and I think the methods to make maximum use of your energy haven't kept up. I'm seeing something like an x10 where all your boat's energy creators and energy users are controlled from a central point, of course remotely if needed, from a variety of platforms, etc. Beyond my skills to develop one.

[valhalla360]

Originally Posted by CatNewBee

Attachment 174428
One or two of them are very often shaded, but anyway, the figures are based on the victron MPPT monitor / history. It helps to clean the panels from time to time...

I was referring to the OP's idea where they would have some on the bimini and some on the main cabin.

In the picture, it looks like yours are behind the bimini and the boom. That works fairly well as it's often outside of the shadow. Up on the main bimini and cabin, they are mostly in the shadow.

The OP didn't say what size boat he's talking about. On a big cat getting 1000-1500w way at the back is possible...of course on a big boat a 5k btu air/con is going to be very limited in what it can do.

[valhalla360]

Originally Posted by wallythacker

No, I'm not hanging a dozen off the back, 4 or 5 like the picture shown and 6 flexible on the bimini and my cabin roof can handle 4 more.

14 panels @150w = 2100 potential watts.

It shouldn't be too hard to engineer something that disconnects the AC when another large load goes online like the watermaker. The AC can come back online when the watermaker shuts down.

I'm beginning to think there's a lot of room for better power management on boats. The power plants have evolved quickly and I think the methods to make maximum use of your energy haven't kept up. I'm seeing something like an x10 where all your boat's energy creators and energy users are controlled from a central point, of course remotely if needed, from a variety of platforms, etc. Beyond my skills to develop one.

The problem isn't the instantaneous load. No problem getting an inverter that will run the air/con or even the air/con and water maker plus a few other items (well there are $$$ but otherwise no issue).

The problem is feeding it. For that you need watt-hrs generated and stored. Solar panels on the bimini and cabin won't produce anything close to what unshaded panels will produce.