A/C that runs off a battery...

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Jimmyt
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Re: A/C that runs off a battery...

Post by Jimmyt » Thu Jun 10, 2021 6:45 am

Am I understanding this things purpose correctly? Going back to Clark's 3rd video at 16:25 and he's talking about how much to fill based on the moving of the frost line up his evaporator. Where the frost line ends is where the fluorocarbon is fully evaporated (no liquid left). He uses amount added to dial that in, but also comments how things have to reach steady state and takes hours. This gizmo's sensor part is placed at the end of the evaporator tubing and detects that frost line approaching it by its temperature. As it gets colder, it starts closing off the valve so the frost line (and more importantly the liquid) doesn't pass the sensor and into the compressor??? Since it's variable, it doesn't rely on Clark's "steady state" and it can deal with the wild swings of the room's environment???
You have the concept. Remember, Clarke is charging a refrigerator to work in 10-20 deg space. No airflow over the evaporator.

Charging an air conditioning system doesn't require that long to reach a fairly steady state condition - regardless of the expansion device used.

The TXV will compensate for a variety of conditions, which is why you need to watch the head pressure while you are charging. The system may start cooling well before the charge is correct. You have to keep charging until the head pressure makes sense.

The TXV or other expansion device, goes right in front of the evaporator. It is the pressure differential created by the expansion device, that makes the system work. The reduction in pressure in the evaporator causes the refrigerant to boil (when you reduce the pressure of a liquid, the boiling point temperature drops). When the liquid starts boiling, it takes in heat. Thus, the cooling effect.
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Re: A/C that runs off a battery...

Post by Jimmyt » Thu Jun 10, 2021 6:58 am

That TXV would probably work, but I was looking at a name brand that was adjustable and had a specified capacity range. $134 if I recall.

The one you are looking at has an external equalizer line which connects to the suction side of the evaporator in the general vicinity of where you put the thermal bulb.

At $16, if it doesn't work you can always sprinkle it on your breakfast cereal.
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Re: A/C that runs off a battery...

Post by OverEasy » Thu Jun 10, 2021 1:19 pm

Not to be absurd but something I did in university (in East Texas) where I couldn’t afford a place with A/C during the summers was the:
“Window Fan Swamp Cooler”

A tray with ice (long narrow loaf pan) and water was placed securely(ish) :o above the discharge of a box fan.
A section of bed sheet with slits was draped from the top ice/water tray across the face of the fan and into another tray.
Wet sheeting then turn on on low fan then enjoy a 10 to 15 degree temperature drop due to evaporation.

Use one of those really nice Aplincool 12 VDC Ice makers to create the ice (and cool beverages of choice)
Use one of those fancy energy efficient West Marine type 12 VDC fans.
Two bread loaf pans and an piece of bed sheet

VOILA!!! Low tech redneck A/C!!!
( :D :D Leastawaysuntilyourunoutofice&/orvoltage :D :D )

Don’t laugh too hard….it worked and they are still selling variations today as personal desktop air conditioners :D :D :D :D like below.
The above is just a little larger and multi-functional.. fan works by itself… bread tins for baking bread ….. bedsheet for clean-up :D :D

Image

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Re: A/C that runs off a battery...

Post by Jimmyt » Thu Jun 10, 2021 4:38 pm

pleb222 wrote:
Tue Jun 08, 2021 7:04 am
I use the Zero Breeze in my Mac26m. It's a mini compressor AC unit, about 2500 btus, has it's own lithium battery, has dual hoses for air exchange to the outside, very easy to use. It works very well to take the edge off at night, we can get quite a few degrees down.

https://www.zerobreeze.com/products/zer ... 2MQAvD_BwE
Sorry I missed this earlier. I saw a video on these when they were first starting up. I didn't even know they were actually producing them yet.

That is exactly the right capacity for the vberth or aft cabin areas in 90 deg F weather down this way.

You state you have dual hoses for the heat rejection. Sounds like a really neat system. If you have any performance info like outdoor temp/humidity and conditions in the cabin that your system achieves - we'd love to hear about it. Also, any info about how long the unit runs on a charge would be interesting.

I really like the way they packaged it.

Thanks for chiming in!
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Re: A/C that runs off a battery...

Post by Inquisitor » Thu Jun 10, 2021 5:37 pm

Sure would like to get some information on that compressor
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Re: A/C that runs off a battery...

Post by OverEasy » Thu Jun 10, 2021 11:52 pm

That little unit is cool!

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Re: A/C that runs off a battery...

Post by Inquisitor » Fri Jun 11, 2021 4:46 am

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Re: A/C that runs off a battery...

Post by adudinsk » Fri Jun 11, 2021 10:38 am

My brother had a vintage VW camper van (yeah.. a burning man type of guy).. and he bough a swamp cooler for the window.
In my area.. does not work.. we are WAY WAY to humid .. if you go to ... say Vegas.. works ok..
Still nothing beats a compressor unit.



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Re: A/C that runs off a battery...

Post by Inquisitor » Fri Jun 11, 2021 10:53 am

adudinsk wrote:
Fri Jun 11, 2021 10:38 am
My brother had a vintage VW camper van (yeah.. a burning man type of guy).. and he bough a swamp cooler for the window.
In my area.. does not work.. we are WAY WAY to humid .. if you go to ... say Vegas.. works ok..
Still nothing beats a compressor unit.



AD
Being a southern (eastern) boy I agree... up to "Still nothing beats a compressor unit". Out west... NOTHING beats a swamp cooler! You need moisture, you need cool. A swamp cooler supplies both VERY efficiently. A compressor can't touch it.
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Re: A/C that runs off a battery...

Post by OverEasy » Fri Jun 11, 2021 11:42 am

:D :D so East Texas drier than where you are ?? :o
Wow!… We used to whittle chairs out of the humidity in East Texas to sit on… :D :D

Yes a compressor based A/C system is always going to beat a swamp cooler for getting cold any day of the week. The challenge is significant cost, complexity, longevity, serviceability and durability.

Yes, the swamp cooler is a bit on the absurd side (especially the desk top model :D :D ) but to some “degree” they DO WORK.

In house sized installed systems the water is chilled in an outside based louved evaporator chiller and the cooled water is then circulated through an interior exchanger across which the interior house air is circulated. The interior air is cooled and dehumidified. The moisture condensates are drained away. The interior house air is cooler and drier.

The “window fan swamp cooler may not do much about the humidity but it does cool the air.

One innovative cruiser I came across a decade or two ago when at anchor used a closed loop tube down 20+ feet in the water to bring up cooler water that he ran through a shell and tube exchanger to cool his cabin air. It was definitely cooler and drier.
Same process as the house swamp cooler but without the evaporator as this was more akin to a portable geothermal.

He had his system running both on battery power for the circulator pump and air mover blower AND the circulator pump could be wind driven should that be available.

Note: For those unfamiliar with house hot water hydronic heating systems a circulator pump doesn’t lift water like a well pump. It just circulates water I a closed loop which has significantly less power requirements even for multi story houses. Recall that for these purposes water is an incompressible and if one pushes water from discharge side of the circulator pump water is both pushed and drawn into the inlet side of the pump.

The point is there are multiple ways to get to the same destinations of being more comfortable in hot weather wherever one happens to be :D :D and it doesn’t have to cost a fortune. The little fancy rectangular boxy A/C thingy pictured earlier costs between $900 to over $1800 depending on the number of 24 VDC battery packs it comes with.

A large Alpincool 12 VDC refrigerator/freezer is relatively cheap in comparison given it can also cool the beverage of choice… :D :D

Have fun!!

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Re: A/C that runs off a battery...

Post by OverEasy » Fri Jun 11, 2021 1:42 pm

Given your latest hobby Inquisitor we thought you could appreciate this billboard:

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Re: A/C that runs off a battery...

Post by Inquisitor » Fri Jun 11, 2021 3:30 pm

OverEasy wrote:
Fri Jun 11, 2021 1:42 pm
Given your latest hobby Inquisitor we thought you could appreciate this billboard:

Image
:D :D Hobby! :D Yes... I love it so much... I'll come do yours for free because it's just so fun.

Have had a couple days off due to drenching downpours... might be able to have fun again tomorrow morning. :(
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Re: A/C that runs off a battery...

Post by OverEasy » Mon Jun 14, 2021 8:59 am

Hi Inquisitor!

We appreciate all the detail you put in your posts. Thank you!

We’re looking at possibly using a ‘solar generator’ approach as a possible option to one of those combustion inverter generators to supply power for an A/C system.

I believe you once mentioned the functional charge rate of solar and time to recharge lead-acid vs. Li base batteries but we can’t seem to find it now :(

Could you point us in the right direction?

Thanks!

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Re: A/C that runs off a battery...

Post by Inquisitor » Mon Jun 14, 2021 2:13 pm

OverEasy wrote:
Mon Jun 14, 2021 8:59 am
Hi Inquisitor!

We appreciate all the detail you put in your posts. Thank you!

We’re looking at possibly using a ‘solar generator’ approach as a possible option to one of those combustion inverter generators to supply power for an A/C system.

I believe you once mentioned the functional charge rate of solar and time to recharge lead-acid vs. Li base batteries but we can’t seem to find it now :(

Could you point us in the right direction?

Thanks!
I sure wish those solar generators were some kind of silver bullet and I hate to rain on your idea, but they're not going to even come close to helping. Let me just hit some of the highlights why it's not going to work.
  1. Maybe there is a better, cheaper A/C unit, but a cursory Amazon check found the GE 5000 BTU unit for $144. I think this predecessor's was the one I put in the M for the aforementioned B.E.E.R. Cruise. It sounds like a truck in and out of the boat. It uses about 500 watts of power.
  2. The small Honda's (or equivalent) will easily handle it running even in their quiet mode. IOW the A/C is louder than the generator.
  3. As I understand it, these "solar generators" are a very convenient assembly of parts that I have discussed at the component level in my Inqism-03 and/or the Battery Build.
    1. 200 watts of solar panels
    2. 1000 Whr battery - Typically they use LiFePO4. This is about 75 A-hr or a little better than a Type 24 battery lead-acid battery can safely provide.
    3. Most have a BMS, the cheap Chinese ones sometimes don't
    4. Charge Controller - some are good, some are cheapest PWM models.
    5. It has an Inverter, the cheap Chinese ones use Modified Sine Wave (Not good) . You want a Pure Sine Wave - Its more efficient and won't destroy you sensitive electronics and motors.
  4. A 1000 W-hr - great for radios, lights, etc, but it'll only run the A/C for 2 hours.
  5. It would be questionable whether panels could recharge a fully discharged unit in a day.
  6. The conversion from DC to AC with a good Pure Sine Wave Inverter as we calculated in the other thread is only about 85% efficient.
  7. Before investing in one, at the very least try to find out what it has inside. You might also try looking into this guy's Play List for solar generators. He's not very flattering on them in his tear-downs. Most are filled with second rate junk (his words) that guarantee built-in-obsolescence. Might see if one you are considering is in his list. https://www.youtube.com/playlist?list=P ... Qxb3DumV-y
This is why I'm looking at Clark & Emily's approach and brought it up here.
  • a more efficient and quite compressor
  • no loud fans
  • try to use efficiencies of a silent water cooled condenser loop
  • no DC/AC conversion losses
  • But Jimmy has me about convinced that something that is powerful enough to cool down just the berth will barely last the night... even with my large 3500 W-hr battery. And even if it did, I wouldn't be able to re-charge that with my measly 200 watts of solar panels.
I'm not sure if I answered your question. I don't recall using the term "functional charge rate". I recall saying that LiFePO4 has a better chemical conversion efficiency. It's around 98% while lead-acid is in the 80 to 90% depending on quality of battery and whether its gets trickle charged.
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Re: A/C that runs off a battery...

Post by Jimmyt » Mon Jun 14, 2021 3:06 pm

But you are definitely on the right track. Reduce the load as much as possible. Then, power up to do what it takes. So, maybe you run your Honda gen set during the day to recharge your batteries - if your solar won't quite get there. You won't be able to hear it over the buzzing of the jet skis or the cacophony of V8 speed boats with straight header exhausts. Or maybe you build a wind generator to augment your solar. :wink:

Don't mistake me for a naysayer. I'm cheering you on, and only injecting a taste of numbers when absolutely necessary. You've got a great concept. After all, they're selling something remarkably similar for $1,000. A water-cooled version could probably beat the efficiency up a few points.

At 2,500 btu/hr, you want to have an evaporator fan set at about 85 cfm (cubic feet per minute) while blowing through your cooling coil and any associated ductwork. Speed control (PWM or other solid state method - preferably not resistance) on both the compressor and evaporator would allow you to modulate the system to increase efficiency and reduce power usage during off-peak operation.

Never give up; Never Surrender! 8)
Last edited by Jimmyt on Mon Jun 14, 2021 3:08 pm, edited 1 time in total.
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