Overnight Cooling Without Shore Power

[rslifkin]

LFP isn't more electrically efficient, but it's more weight / space efficient.

[mvweebles]

Originally Posted by a64pilot

None of that is efficiency.
Efficiency is most often considered the amount of power you can get out of a storage source compared with the amount of power you put in.
For example a lead acid battery requires on average to have to have 102% to 106% of the power removed to be put back, if you only return what you took out then over time of course your walking the charge down.


So if an LFP battery is 100% efficient as in you only have to return what you take out, then it’s only between 2% and 6% more efficient than Lead, I have no idea about LFP, but nothing is 100%, nothing.
Most of what you said is simply not true either, like only 300 to 500 cycles or being horribly sensitive to discharge below 50%. The 50% is simply an arbitrary number that was picked back in the day as one that was considered a good trade off of usable capacity and cycle life, and if they only lasted 300 cycles, then that’s less than a year, and most get well more than a year out of their banks.

But I do agree that if you want to run AC’s off of a battery bank overnight, then that really does make more sense with an LFP bank, just I think running AC’s overnight off a battery bank to be a foolish endeavor, cause if nothing else, it’s the heat of the day when AC is needed, not the cool of the night.

The world is changing - and you may want to spend a bit of time on the newer technologies out there. If you want a narrow definition of efficiency to justify 100-year old technology, I won't argue with you (though I will point out that the self-discharge rate on Lead Acid is many multiples of LFP, certainly a measure of efficiency; or the power-density of LFP, or the lifespan, or any other measure of efficiency except the narrow one mentioned). Nothing wrong with Lead Acid in some instance, but let's be honest: if lead acid were the state-of-the-art, Tesla would be out of business; and off-grid solar would be non-existant. A lot has changed over the last 10-years.

Decent article on comparing lead acid to other battery types HERE.

For example, most golf cart batteries are rated for about 550 cycles to 50% discharge - which equates to about 2 years

How does that compare to Lithium? Here's the data sheet for Battle Born 100A/12VDC, the most likely and popular replacement battery for many in our category.

*Approximately 75-80% of the battery capacity will remain after 3000 cycles in applications recharging at 0.5C or lower. We have seen life spans well over 5000 cycles in our lab testing

Trojan T105's weigh about 70lbs and cost around $160/each delivered. Battle Born drop-in replacement for a T105 weighs 30 lbs, and is $1000/each and will easily sustain 80% DOD, meaning it delivers 80AH vs the T105's 55AH, almost 50% more energy. And it lasts 10x more duty cycles. And it is half the weight. Yes, it's about 6x more expensive, but over the long run, it's much, much less expensive. And it doesn't require frequent replacement and maintenance. Aforementioned self-discharge rate of 5%-10% per month for Lead Acid. And the list goes on and on.

But this is a thread about efficient cooling. Efficient batteries are a key reservoir (again, the Tesla example). Battery efficiency (yes, efficiency) combined with quantum leaps in cooling efficiency make this possible. No idea if the OP has cracked the code, but someone will. Residential AC efficiency has made huge leaps in the last 15-years. No reason that can't apply to boats.

There is a solid market for efficient cooling which, for all practical purposes, needs to be combined with efficient battery banks. To the OP - do not be discouraged by the comments here. There are tons of people in South Florida who would use their boats more if it were comfortable.

Peter

[mvweebles]

Originally Posted by rslifkin

LFP isn't more electrically efficient, but it's more weight / space efficient.

A very narrow definition. There are many ways to measure efficiency. Yes, weight-wise as you mention. They also have much lower resistance which means more efficient energy delivery in hi-draw situations. Self-discharge is 80% lower than Lead Acid. They are light and maintenance-free which means you can stow them out-of-the-way versus in the middle of your mechanical spaces.

If that isn't efficient, well, we'll just have to agree to disagree.

Peter

[Muaddib1116]

Originally Posted by a64pilot

it’s the heat of the day when AC is needed, not the cool of the night.

I run hotter than most, and when I'm in the tropics, I can usually deal with the heat during the day as long as there's shade, a breeze or fans. But at night, I have a lot of trouble sleeping if it's even a little bit warm. To be fair, I'm from New England so I'm not acclimated to the climate, and your body won't acclimate on a short week or 2 week trip. I am hopeful that when I head south that I can acclimate over time, but I may eventually need to explore cooling solutions. So to the OP, I say if you have an idea that is actually new and actually works, go for it, there will be a market.

[RaymondR]

I live in tropical Australia and have done so since 2002. Other than tying up at a jetty with mains power and sticking a small aircon in the companionway I have found the best solution the one I now use.

I have a boat with large deck hatches in the saloon and the forward cabin where I sleep (single hander) I have two 12 V auto radiator fans mounted in plywood which fit into the hatch surrounds. The fans are wired in series with a motor speed controller. They are in series because it allows me to use a single speed controller and if run at full speed make to much noise and blow a small gale.

Staying cool on a boat on the water is largely a matter of keeping lots of fresh air moving through the boat and the radiator fans do a great job of this even when there is no breeze.

As can be seen in the attached image the fans do not intrude physically into the boat and are easily stored when not in use.

[GordMay]

Greetings and welcome aboard the CF, Kate.

[Tupaia]

Cheap and cheerful
www.Icybreeze.com


Less cheap
www.zerobreeze.com

[waterman46]

To run a small AC overnight on battery is possible, with a very large battery bank. All depends on how much cooling you require. But then you need to recharge, so unless you have a very large solar array and good tropical sun, you need to run a generator a few hours to recharge. Again, all depends on size of AC unit, insulation of cabin and temperature desired.



Personally, we use a small 110V fan run off our invertor, or a different small fan running off 12V, for cooling on the boat. Had AC but removed it to get the storage space. The fans work well enough for us on our recent trip through Panama. This was in December and January. For summer, well, we need a bigger fan!



In the tropics the problem is not the temperature, it is the humidity. You sweat and it doesn't dry, but you get used to that. In a dry climate like CA or Pacific Mexico, we had temperatures in the 90's that did not feel uncomfortable. In Panama a temperature of 85 inside the boat felt uncomfortable and you want to have a breeze or a fan. I might look into some device that could reduce humidity in the boat. But then you start having to close the hatches and ports, eliminating fresh air flow. I don't enjoy being closed up in the boat, even if it is cool inside and hot outside. Might as well stay home.

[FabioC]

I would say that at certain latitudes, being able to cool down the cabin at night while at anchor would be a first priority.
Recently, I chartered a boat in Belize. The boat did not have a generator. We always anchored out and at night the heat was brutal. We spent about half the nights sleeping in the cockpit because downstairs was simply impossible. A few nights, however, there were squalls passing through, so sleeping in the cockpit did not work either...
The boat did not have a generator (I noted it down as a must-have for future charters in the tropics). A generator is not a perfect solution either, because it is quite noisy, it kind of ruins the pleasure of sleeping in a quiet, isolated anchorage.
So, if you have a solution that works as a standalone, it is effective, and it is relatively quiet (or at least quieter than a generator), I think you'll be rich.
BTW, if such a device exists, there are many other use cases as well for it.

[Muaddib1116]

What a large lithium bank can do for you, if it is large enough to run an ac unit all night, is make your generator use more efficient. You can run down your battery bank at night and then run the generator at full charging load just long enough to recharge the bank, rather than running it at variable loads all night with only the ac drawing on it. Also, if you have good solar/wind, then the generator only has to supply what those systems can't, which is even less use.

[a64pilot]

Originally Posted by mvweebles

The world is changing - and you may want to spend a bit of time on the newer technologies out there. If you want a narrow definition of efficiency to justify 100-year old technology, I won't argue with you (though I will point out that the self-discharge rate on Lead Acid is many multiples of LFP, certainly a measure of efficiency; or the power-density of LFP, or the lifespan, or any other measure of efficiency except the narrow one mentioned). Nothing wrong with Lead Acid in some instance, but let's be honest: if lead acid were the state-of-the-art, Tesla would be out of business; and off-grid solar would be non-existant. A lot has changed over the last 10-years.

Decent article on comparing lead acid to other battery types HERE.

For example, most golf cart batteries are rated for about 550 cycles to 50% discharge - which equates to about 2 years

How does that compare to Lithium? Here's the data sheet for Battle Born 100A/12VDC, the most likely and popular replacement battery for many in our category.

*Approximately 75-80% of the battery capacity will remain after 3000 cycles in applications recharging at 0.5C or lower. We have seen life spans well over 5000 cycles in our lab testing

Trojan T105's weigh about 70lbs and cost around $160/each delivered. Battle Born drop-in replacement for a T105 weighs 30 lbs, and is $1000/each and will easily sustain 80% DOD, meaning it delivers 80AH vs the T105's 55AH, almost 50% more energy. And it lasts 10x more duty cycles. And it is half the weight. Yes, it's about 6x more expensive, but over the long run, it's much, much less expensive. And it doesn't require frequent replacement and maintenance. Aforementioned self-discharge rate of 5%-10% per month for Lead Acid. And the list goes on and on.

But this is a thread about efficient cooling. Efficient batteries are a key reservoir (again, the Tesla example). Battery efficiency (yes, efficiency) combined with quantum leaps in cooling efficiency make this possible. No idea if the OP has cracked the code, but someone will. Residential AC efficiency has made huge leaps in the last 15-years. No reason that can't apply to boats.

There is a solid market for efficient cooling which, for all practical purposes, needs to be combined with efficient battery banks. To the OP - do not be discouraged by the comments here. There are tons of people in South Florida who would use their boats more if it were comfortable.

Peter

Your missing one inescapable fact, that is a battery is a storage device, oh and self discharge rates for a battery that is cycled daily is irrelevant.
But back to the it’s only a storage medium, the Tesla or any other electric car works because they are often plugged into the grid or recharge. Remove the grid and an electric cars doesn’t work, and boats at anchor don’t have grid access.

So how are you going to recharge your Lithium bank while at anchor? I can tell you, only one realistic way, and that’s to run a generator.
Now while it’s true that you can spend a bunch of money and buy a BIG generator to charge a massive LFP bank in say half a day so that it can run AC all night, you have a BIG, HEAVY generator to do that, and a whole bunch of $$$ in an LFP bank, and guess what, your still running a generator.

Why not spend 1/10 the money on a small lightweight Diesel generator and just run it when you want AC? Shed loads less money, less weight, a whole lot less complex, and even if you buy one every few years, your still money ahead.

It’s a lot like what I am sure will soon be a “thing” a hybrid, probably a Catamaran, massive LFP bank sold on the theory of being “green” with electric sail drives, and a BIG generator.
In fact I’m pretty sure I saw one at Staniel Cay when we were passing thru, I didn’t get real close, but feel sure I saw HYBRID in big letters.

But bottom line, unless it plugs in regularly to use grid power, it’s going to burn Diesel to charge that huge LFP bank and to motor the thing when it moves, less efficiently than if it drove the boat directly.

Residential cooling hasn’t I don’t think made big strides in the last 15 years or so, but did previously, mostly by having huge condensers which improves efficiency, but drives up cost and unit size, but also ones I put in my house were at the time the most efficient there were, it had dual compressors, it would run the big one if it had to, but most of the time ran on the small compressor, which had the effect of further increasing the size of the condenser. Oversizing the evaporator and condenser means the system doesn’t have to run as cold, which lets the compressor operate at a higher COP, or coefficiency of performance.

Now why can’t you do that on boats? Well two reasons, first except for a small niche market, there is no demand, but the second reason is size. You can become more efficient, but it’s going to be likely physically twice as large, and that will hurt sales. Most on yachts don’t care how much power the AC consumes, but they do care if it’s noisy or takes up a whole storage area.

One day LFP will likely replace lead, logically it should, what’s keeping it from not doing it today is I believe complexity which leads to expense, but mostly because as far as I know you can’t buy a true drop in solution, something that is sold at West Marine etc.
I would expect to have already seen it in higher end expensive boats, surprised I haven’t yet, but I think once it becomes common in new builds, then you will see retrofit kits, maybe.
Honestly surprised they aren’t sold now.


Just looked it up, the average SEER of a residential unit sold in 2006 was 13.07, the average unit sold in 2020 is 13.66.
Now that’s an increase, but I wouldn’t consider it a huge increase.
https://www.achrnews.com/articles/10...dential-sector

I believe the current ceiling is about mid 20’s SEER, but admittedly as I haven’t looked at house AC’s in quite awhile it may be higher.

[mvweebles]

Originally Posted by a64pilot

Your missing one inescapable fact, that is a battery is a storage device, oh and self discharge rates for a battery that is cycled daily is irrelevant.
But back to the it’s only a storage medium, the Tesla or any other electric car works because they are often plugged into the grid or recharge. Remove the grid and an electric cars doesn’t work, and boats at anchor don’t have grid access.

So how are you going to recharge your Lithium bank while at anchor? I can tell you, only one realistic way, and that’s to run a generator.
Now while it’s true that you can spend a bunch of money and buy a BIG generator to charge a massive LFP bank in say half a day so that it can run AC all night, you have a BIG, HEAVY generator to do that, and a whole bunch of $$$ in an LFP bank, and guess what, your still running a generator.

Why not spend 1/10 the money on a small lightweight Diesel generator and just run it when you want AC? Shed loads less money, less weight, a whole lot less complex, and even if you buy one every few years, your still money ahead.

It’s a lot like what I am sure will soon be a “thing” a hybrid, probably a Catamaran, massive LFP bank sold on the theory of being “green” with electric sail drives, and a BIG generator.
In fact I’m pretty sure I saw one at Staniel Cay when we were passing thru, I didn’t get real close, but feel sure I saw HYBRID in big letters.

But bottom line, unless it plugs in regularly to use grid power, it’s going to burn Diesel to charge that huge LFP bank and to motor the thing when it moves, less efficiently than if it drove the boat directly.

Residential cooling hasn’t I don’t think made big strides in the last 15 years or so, but did previously, mostly by having huge condensers which improves efficiency, but drives up cost and unit size, but also ones I put in my house were at the time the most efficient there were, it had dual compressors, it would run the big one if it had to, but most of the time ran on the small compressor, which had the effect of further increasing the size of the condenser. Oversizing the evaporator and condenser means the system doesn’t have to run as cold, which lets the compressor operate at a higher COP, or coefficiency of performance.

Now why can’t you do that on boats? Well two reasons, first except for a small niche market, there is no demand, but the second reason is size. You can become more efficient, but it’s going to be likely physically twice as large, and that will hurt sales. Most on yachts don’t care how much power the AC consumes, but they do care if it’s noisy or takes up a whole storage area.

One day LFP will likely replace lead, logically it should, what’s keeping it from not doing it today is I believe complexity which leads to expense, but mostly because as far as I know you can’t buy a true drop in solution, something that is sold at West Marine etc.
I would expect to have already seen it in higher end expensive boats, surprised I haven’t yet, but I think once it becomes common in new builds, then you will see retrofit kits, maybe.
Honestly surprised they aren’t sold now.


Just looked it up, the average SEER of a residential unit sold in 2006 was 13.07, the average unit sold in 2020 is 13.66.
Now that’s an increase, but I wouldn’t consider it a huge increase.
https://www.achrnews.com/articles/10...dential-sector

I believe the current ceiling is about mid 20’s SEER, but admittedly as I haven’t looked at house AC’s in quite awhile it may be higher.

You realize the link you used to support your position that AC efficiency has only improved marginally is from 2007, right?

To the OP - there are plenty of people who prefer to be cool than not, especially if it can be done cost effectively without a lot of bells and whistles to maintain. If you have anything remotely resembling what your original post insinuates, you've got a winner.

Good luck!

Peter.

[Scotty Kiwi]

If I could get by in the tropics without running AC, or better, without having AC, I would. Savings in weight, space, therefore boat size, complexity, repairs, 5/10 year refit.

With this philosophy, in many boats I've often gotten by just with 12v fans, hatches open with mossie nets.

[scarlet]

we have a small portable AC unit that we set up for the master hull only. Doesn't draw much... and it brings the temp down enough to be comfortable.

[J Clark H356]

My wife won’t cruise without AC full time. We run our 5KW Northern Lights diesel when not in the dock. I use about .25 gal of diesel per hour, between 5 and 6 gallons in 24 hours. It’s a trade off we make so we go at all. Neither one of us likes extreme heat or cold so our water to air heat pump works for both. We also don’t have mildew problems because our interior environment is more humidity controlled. Both temperature and humidity are comfort parameters.