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Old 31-08-2016, 15:36   #61
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Re: 12 Volt air conditioner may be availabe soon

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Originally Posted by boatbod View Post
The heading may incorrectly say "BTU to Watt", but the body of that page correctly says:

Power converter
...
BTUs per hour (BTU/hr) to watts (W) power conversion calculator and how to convert.

You can go to another page on that site to directly convert energy, specifically BTU to Watt hours: Energy Conversion - RapidTables.com

As I said earlier, you need to understand the difference between power and energy. You may like to look at:

Amps v Amp hours v Amps/Hr

Quote:
Originally Posted by boatbod View Post
Yes, many air conditioning units claim certain BTU capacity and their stated amperage draws are less than you would expect based on the BTU conversion. So what. Just means someone isn't being truthful with their numbers.
No, it means that they understand how A/C works and you clearly don't.
Converting BTU to Watt hours or BTU/hr to Watts is not a valid consideration. You can't just convert between units to calculate the energy requirements in an A/C system.

A/Cs move heat energy from inside the boat to outside the boat. They just use some electrical energy to do so. The amount of energy required to move that heat is not the same as the amount of energy moved.

A/C systems are essentially heat pumps and have an "energy efficiency rating" or EER which tells you how cooling power relates to energy consumption. That is typically around 3 in the systems we are talking about.

i.e. A typical 5000 BTU A/C will remove 5000 BTU of heat energy (1.465kWh) from an area using 5-600 Watt hours of electricity.


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Old 31-08-2016, 16:02   #62
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Re: 12 Volt air conditioner may be availabe soon

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Originally Posted by svGenesis View Post
I'll restate this again for clarity.

I'm looking for someone who has/is trying to AC or cool a queensize berth, (500 cubic feet ex.) using battery's (Li-PO) Solar (1000w-1200w) and a wind (400w) I expect my set-up to be 500-600ah Li-PO with 1000w solar, and 400w wind, Honda2000w as back up. I have seen people in RV's doing this but, they could easily spin thier genny, I'm looking for someone on a boat who is or has tried it.
Perhaps you aren't hearing from people on boats that have tried it because no one has. It's pretty clear that when you do the math (correctly) it just isn't practical.

If you install enough solar panels and other charging sources and enough LiFePO batteries, sacrifice enough space and add enough weight to the boat then it you might be able to make it work, just wouldn't be cost effective or convenient. At the end of the day it will be cheaper, easier, work better, take less room and be less complicated to just install a generator.

My research on powering air con and other high power applications from 12V DC on boats always comes out the same.
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Old 31-08-2016, 16:41   #63
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Re: 12 Volt air conditioner may be availabe soon

These are about 10 bucks on Amazon. Probably just as practical.
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Old 31-08-2016, 16:41   #64
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Re: 12 Volt air conditioner may be availabe soon

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Originally Posted by skipmac View Post
Perhaps you aren't hearing from people on boats that have tried it because no one has. It's pretty clear that when you do the math (correctly) it just isn't practical.

If you install enough solar panels and other charging sources and enough LiFePO batteries, sacrifice enough space and add enough weight to the boat then it you might be able to make it work, just wouldn't be cost effective or convenient. At the end of the day it will be cheaper, easier, work better, take less room and be less complicated to just install a generator.

My research on powering air con and other high power applications from 12V DC on boats always comes out the same.
I'm with you, I've run the numbers and it is a large requirement. The reason i'm looking is it seems that some RVers are beginning to make it work at least on a short term basis. My other thought is most cabins heights are 6'-6.5' and a multi hull cabin beam is small so the cubic feet on a boat is less than say a house or RV. Just looking for feedback from someone who has tried it.
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Old 31-08-2016, 18:04   #65
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Re: 12 Volt air conditioner may be availabe soon

StuM, I most certainly do understand exactly what I'm talking about and have several decades of practical experience and training in the electrical field. That said, it's pointless to argue with you further because as far as I can see you are just trolling for a fight.
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Old 31-08-2016, 18:33   #66
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Re: 12 Volt air conditioner may be availabe soon

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Originally Posted by a64pilot View Post
My little 3.5 KW Diesel generator is good for right at 30 amps, my boat and most smaller sailboats have a 30 amp electrical system so no real need of having much more generator unless you have a 50 amp boat. It's electrical output running two AC's, the TV, fridge and all the other stuff is 21 amps on average, and it burns one quart of fuel an hour or four hours per gallon of course.
I will soon have a kilowatt of Solar and I have a large inverter, but I can tell you from experience that my little 5,000 BTU AC will chew through my 660 AH bank in short order. I feel sure I would need at least 2 KW of Solar and at least a 1000AH lead acid bank to run the little AC and that would just cool the front Stateroom, but one quart of Diesel an hour will cool the whole boat and run everything else and charge the bank too.


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Thanks a64pilot. I personally would be prepared to pay a few dollars a night in summer for a cool nights sleep. Diesel powered electricity generators are very cost effective and energy efficient. Adding solar and a significant LithPo4 battery bank will aid in reducing daily operational costs as well.

I'm thinking a hybrid system of wind, solar and diesel is the solution offering the best power bang on a floating platform. Like everything the devil is in the details.

If you want to conserve energy usage you can for instance have a separate ac for the master cabin. That's if your not intending to have others on board most of the time. Otherwise it would be hard to explain to everyone else why you get to have the ac and they have to suffer.

Personally I'm going for max solar, max LithPo4 battery bank and perhaps a two genset solution.

The more calculations that can be provided by those out there using ac is very much appreciated.

Again thanks,

Chaya
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Old 31-08-2016, 19:04   #67
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Re: 12 Volt air conditioner may be availabe soon

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Originally Posted by Ironman162 View Post
Just by way of interest, from what I can make out, Zero Breeze is a portable, rechargable aircon with its own battery.

Its rated to last for 5 hours.

This should limit the power drain on the battery system overnight and during the day there should be enough solar to charge and run it in Summer or thats the idea.

Granted it has limitations but I havent seen a better idea within the price bracket of approx $300 to $400 for a pre order.

One cant help wondering how a car aircon would go driven by a DC motor, petrol engine or equivalent?
My electric winch motor takes 100A under full load but I feel sure an aicon will take less at a duty cycle.

Just an idea anyway....
Hmmmm... This machine appears to be operating completely inside of a tent, cooling the entire space without a vent to the outside for heat extraction. Something fishy about that? I bet the investors are going to see great returns on their money...
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Old 31-08-2016, 19:58   #68
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Re: 12 Volt air conditioner may be availabe soon

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Hmmmm... This machine appears to be operating completely inside of a tent, cooling the entire space without a vent to the outside for heat extraction. Something fishy about that? I bet the investors are going to see great returns on their money...
Look at their page again there is a hose that hooked up to the hot side to vent the warm air outside of the space being cooled.
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Old 31-08-2016, 20:08   #69
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Re: 12 Volt air conditioner may be availabe soon

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Look at their page again there is a hose that hooked up to the hot side to vent the warm air outside of the space being cooled.
I stand corrected
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Old 31-08-2016, 20:13   #70
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Re: 12 Volt air conditioner may be availabe soon

I am watching it to see if it actually does as advertised and some real world data
It may actually be a good option for the main salon on my little islander ( the main is only about 8x10 with 5 foot headroom so about 80 sq feet ) just want cooling for sleep cycles don't need it for daytime.
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Old 31-08-2016, 20:22   #71
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Re: 12 Volt air conditioner may be availabe soon

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I am watching it to see if it actually does as advertised and some real world data
It may actually be a good option for the main salon on my little islander ( the main is only about 8x10 with 5 foot headroom so about 80 sq feet ) just want cooling for sleep cycles don't need it for daytime.
Yep! If that thing functions efficiently and they work out all the bugs then i can see a few of those as at least making things more bearable during hot evenings.
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Old 31-08-2016, 20:39   #72
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Re: 12 Volt air conditioner may be availabe soon

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Originally Posted by svGenesis View Post
I'm with you, I've run the numbers and it is a large requirement. The reason i'm looking is it seems that some RVers are beginning to make it work at least on a short term basis. My other thought is most cabins heights are 6'-6.5' and a multi hull cabin beam is small so the cubic feet on a boat is less than say a house or RV. Just looking for feedback from someone who has tried it.
RV's generally have a ton of space for panels. Almost the entire roof can be panels. I've got about 450W on the roof of my smallish 26' motorhome, and could easily double or maybe even triple that. So room for panels is widely available. No way can I ever come close to that on a 30' monohull. (Big cats could do it easy tho)

During the day, I have no problem with coming up with a system that could run a AC off the panels with a bit of battery for shade and peaking on starts. So it makes sense if you can get 1KW of panels on a roof.

RVs (crap as they are) are generally better insulated than boats. Not good, mind you, but a bit better.

RVs almost always have a generator. Thus AC off of solar during the day when it's available, genset at night. Power budget is brutal off of batteries.
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Old 31-08-2016, 20:53   #73
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Re: 12 Volt air conditioner may be availabe soon

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Yep! If that thing functions efficiently and they work out all the bugs then i can see a few of those as at least making things more bearable during hot evenings.
Heck if it works good enough it would be worth it to enclose my sea berth completely .
And turn the fan down to get longer run times on the batteries and run it of of the load side of solar controller set to run for 2 to 4 hours with a high power cut off. Setting
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Old 31-08-2016, 22:25   #74
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Re: 12 Volt air conditioner may be availabe soon

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StuM, I most certainly do understand exactly what I'm talking about and have several decades of practical experience and training in the electrical field. That said, it's pointless to argue with you further because as far as I can see you are just trolling for a fight.
Not trolling at all.

I'm just trying to help by correcting wrong information and educating others who may be misled by your statement into thinking that it takes 1kWh (or 1 BTU) of electrical energy to move 1kWh ( or 1 BTU) of heat energy out of an enclosed area.

Thinking that is true who would lead others to make the same mistake that you made in grossly over-estimating the electrical energy required to drive an A/C of a given size.

If you disagree with my statements, please explain for the benefit of all where I am wrong. I'm quite happy to acknowledge an error if you can show one.

But just claiming some vague expertise and making accusations of trolling is not helping anyone.
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Old 01-09-2016, 00:06   #75
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Re: 12 Volt air conditioner may be availabe soon

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I sent a question to their Kickstarter site about current draw. They claim that it will cool a 50 square foot room. They don't say how high the room is, how good the insulation is or the outside temperature. Volume, insulation are huge issues. Also, define "cool". If it's 110f and it takes it down to 109.5f, it has technically cooled the room. You won't be able to feel the difference but it will have done it.

You can buy it with a built in 40 amp hour battery, they claim 3.5 hours of run time on high and 5 hours on medium. Without knowing the discharge curve for the battery and what percentage of the charge they plan on pulling out of the battery I hesitate to calculate the amperage draw. Assuming they run the battery completely dead (great way to kill the battery), on medium they are drawing about 8amps at 12v, so about 96watts. My 12k btu unit runs about 10amps at 120v or about 1200w, roughly 12 times the power, so assuming the same efficiency, it's plausible but on a hot day the 12k btu unit runs continuously and the temps can still climb.

I don't have much faith in this being able to cool a cabin when it is 95 degrees outside. I would have zero faith in it cooling anything much bigger than a medium size cooler.

I will be waiting for them to actually being on he market and there are some reports from happy (or unhappy) customers.
Maybe if you use a sleeping bag and vent the cool air directly into the bag. The average human generates something like 75w worth of heat, so it should mostly cancel that out assuming it's very efficient and you start with a cool sleeping bag.
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