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Old 01-09-2016, 00:07   #76
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Re: 12 Volt air conditioner may be availabe soon

Talking about air conditioning I found this old discussion back in 2011 here on CF. Here is one of the CF guys who really know abut solar systems. This is concerning AC on a sailboat.


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Just finished working on a Chris White Atlantic 55 cat in Panama, with a 720Ah x 12V lithium battery system and a Victron 12/3000/120 Quattro inverter/charger with power assist. The inverter can't drive all three (2 x 12k BTU, 1 x 8k) of the boat's AC units at once, but 2 at a time no problem. Can make it through a night on battery/inverter with careful settings.

Installed two American Power 250A x 14V alternators (one on each engine), getting up to 450A x 14V charging with both engines running. So, they can charge back up after an 80% DOD (approx 580Ah) in roughly1.5hrs. Of course, they won't be running the DOD that low all the time so usually the recharging times will be MUCH shorter.

With the lithium batteries there is very little "taper" on the charging, you can get to over 95% full while charging at full blast.

So, yes you can run AC all night on inverter/batteries with careful use...IF you have a serious inverter/battery/charging system. The system on this boat is pretty spendy but certainly nice to have. Also could use a DC genset vs. the aux. engines of course.

Really fun to install this stuff and crank it up to see 450A of charging...however if it was my own budget, I'd likely still consider using a windscoop...;-)
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Old 01-09-2016, 00:08   #77
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Re: 12 Volt air conditioner may be availabe soon

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Does anyone have a setup where they just cool off the sleeping cabin with a 5000/6000 btu unit run solely off of batterys? I am thinking my next boat we will forego a genset and get 600Ah lithiums and 1000-1200 watts of solar and a wind genny.
We used to have the hatch mounted cruise air that was something like 5-7k btu.

It would handle the V-berth at night if you can close it off. During the day, it struggled to do even that.
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Old 01-09-2016, 00:12   #78
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Re: 12 Volt air conditioner may be availabe soon

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I always wondered if a guy couldn't drop a submersible pump overboard deep enough to pick up cooler water, and then run it through a heat exchanger in the cabin. Would only work while moored, of course. But you'd only need power for a small pump and a small fan.
Up north (ie: Great Lakes), that would work to a degree. Actually, I've noticed, the water cooled air/con does seem to put out more cold in cold water vs warm water.

I think the problem with just pumping 50degree water directly up to directly cool the air is you would need a very large heat exchanger or even colder water. I know in very humid conditions, the air/con can freeze up, which implies the cold side of the heat exchanger is below freezing. Now you are talking about it being up around 50-60 degrees.
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Old 01-09-2016, 00:14   #79
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Re: 12 Volt air conditioner may be availabe soon

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Not wanting to get into an argument but I think you'll find that by eliminating the big start up spike you will conserve a lot of energy. As an illustration. And illustration only. In a car if you slam your foot on the gas when taking off you will burn a lot more fast "energy" then if you slowly stepped on the gas.
The flaw in your example is:
- A car in stop&go traffic is accelerating every few seconds.
- An air/con is typically going to start once and then run for at least 10-15minutes often for hours.

Any start up inefficiency is negligible. Also, the inefficiency with gas engines is mostly due to fuel ratios being off during acceleration. On hard acceleration, the engine pumps more fuel into the engine that it can efficiently extract energy from. This is far less of an issue with electric motors.
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Old 01-09-2016, 00:21   #80
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Re: 12 Volt air conditioner may be availabe soon

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Point 1. kW is an instantaneous measure of power. An A/C will require the same number of kW whether it runs for 1 minute or 1 hour. Please learn the difference between power and energy and use the correct units.

Point 2. All of the figures that I have seen for 6000 BTU A/Cs use around 600 Watts or less. i.e. if operating at a 100% duty cycle, they will consume about 0.6kWh to operate for 1 hour.

Where does your 1.7kW come from?
I think the problem is 1.7kW is the energy equivalent to 6000 BTU (I didn't look up to check)

For a heat pump, can beat this as it is extracting cool (incorrect term but easier to understand for layperson) from the cool water under the boat. Result is in real life a water cooled air/con can provide more BTU of cooling than it uses in equivalent electricity.
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Old 01-09-2016, 23:31   #81
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Re: 12 Volt air conditioner may be availabe soon

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Originally Posted by GoingWalkabout View Post
Talking about air conditioning I found this old discussion back in 2011 here on CF. Here is one of the CF guys who really know abut solar systems. This is concerning AC on a sailboat.
it sure is hot in Panama from May to October! dunno that cat though and I have been here for some time.
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Old 02-09-2016, 02:24   #82
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Re: 12 Volt air conditioner may be availabe soon

That A47 was only in Panama for a short time.. Somewhere in the south pacific now.

These days many cats with large solar arrays are able to run all their loads, including occasional AirCon (within reasonable expectations) off solar, with fuel charging as a back up. One such Gunboat 66 ("Slim") has 2.6kW of walk-on Solbian panels on the roof. That boat has Mastervolt Li batteries. We have have our OPE-Li3 batteries on a new modified GB55/57 being commissioned now...lots of solar, big alternators on engines, and no generator.
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Old 02-09-2016, 02:29   #83
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Re: 12 Volt air conditioner may be availabe soon

I've been experimenting with a transition to battery driven air con this summer and have data from 6 nights on the hook that is encouraging. Motivation is the genset is still a noisy distraction inside the boat and I generally feel more at ease with it not running while I sleep (not logical perhaps but it is what it is).

My boat is a Leopard 48. I've installed two Mastervolt 360 lithium batteries for my house and have two 12 volt 150 amp battery chargers that run off the genset and 12 volt 130 amp alternators on each engine. So theoretical charging is 560 amps at 12 volts.

I've done the following test:

1. For the master cabin, I run the air con off the genset for one hour before bed at 10 pm to cool boat to 21 C. Ambient air temp is 30-32C, humidity in the 80-90% range and water temp is 28C. Door to saloon and toilet are kept shut.

2. I keep two 12 volt fridges on all night. Stated amps from manufacturer are 4.88 + 3.6 per hour (Vitrifrigo 210 litre drawer fridge/freezer and 90 litre cockpit fridge. Other minimal use from lights as well but its not material to analysis.

3. At 10 PM turn off genset and set thermostat to 25C and turn on cabin fan. Inverter is turned on and all power comes from battery bank for 8 hours through the night. Obviously while the genset was running prior to 10 pm, it ensured that the house bank was fully charged when AC power was cut 10 pm.

4. I wake up at 6 am and turn off the air con and record amps consumed using Mastervolt Easy View.

5. For the 12000 BTU air con and 2 fridges, the DC consumed has been between 30 and 49 amps per hour. The average over the 6 nights was 37 amps per hour.

6. So I am on average using 296 amps from a 720 amp lithium battery bank to run one air con and 2 fridge units for 8 hours. This is easily recharged the next morning with a combination of motoring or genset. A lot of the discussion above failed to recognise that the air con and fridges will be cycling off frequently throughout the night. Based on my experience, I estimate that the air con and fridges are really only "ON" about 35-40% of the time.

I am very happy with the results and am now planning to add a third 360 amp lithium battery to my house bank to I can run air con in two cabins through the night.
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Old 02-09-2016, 02:35   #84
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Re: 12 Volt air conditioner may be availabe soon

Excellent data! Very much what we hear from our clients about their energy management.

Although I should point out that most of the boats we set up for fast charging are 24V, which is more efficient and saves a lot of weight.
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Old 02-09-2016, 07:45   #85
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Re: 12 Volt air conditioner may be availabe soon

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Originally Posted by HKTim View Post
I've been experimenting with a transition to battery driven air con this summer and have data from 6 nights on the hook that is encouraging. Motivation is the genset is still a noisy distraction inside the boat and I generally feel more at ease with it not running while I sleep (not logical perhaps but it is what it is).

My boat is a Leopard 48. I've installed two Mastervolt 360 lithium batteries for my house and have two 12 volt 150 amp battery chargers that run off the genset and 12 volt 130 amp alternators on each engine. So theoretical charging is 560 amps at 12 volts.

I've done the following test:

1. For the master cabin, I run the air con off the genset for one hour before bed at 10 pm to cool boat to 21 C. Ambient air temp is 30-32C, humidity in the 80-90% range and water temp is 28C. Door to saloon and toilet are kept shut.

2. I keep two 12 volt fridges on all night. Stated amps from manufacturer are 4.88 + 3.6 per hour (Vitrifrigo 210 litre drawer fridge/freezer and 90 litre cockpit fridge. Other minimal use from lights as well but its not material to analysis.

3. At 10 PM turn off genset and set thermostat to 25C and turn on cabin fan. Inverter is turned on and all power comes from battery bank for 8 hours through the night. Obviously while the genset was running prior to 10 pm, it ensured that the house bank was fully charged when AC power was cut 10 pm.

4. I wake up at 6 am and turn off the air con and record amps consumed using Mastervolt Easy View.

5. For the 12000 BTU air con and 2 fridges, the DC consumed has been between 30 and 49 amps per hour. The average over the 6 nights was 37 amps per hour.

6. So I am on average using 296 amps from a 720 amp lithium battery bank to run one air con and 2 fridge units for 8 hours. This is easily recharged the next morning with a combination of motoring or genset. A lot of the discussion above failed to recognise that the air con and fridges will be cycling off frequently throughout the night. Based on my experience, I estimate that the air con and fridges are really only "ON" about 35-40% of the time.

I am very happy with the results and am now planning to add a third 360 amp lithium battery to my house bank to I can run air con in two cabins through the night.
Excellent post thank you this is the real world data that people are looking for .
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Old 02-09-2016, 13:02   #86
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Re: 12 Volt air conditioner may be availabe soon

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Originally Posted by HKTim View Post
I've been experimenting with a transition to battery driven air con this summer and have data from 6 nights on the hook that is encouraging. Motivation is the genset is still a noisy distraction inside the boat and I generally feel more at ease with it not running while I sleep (not logical perhaps but it is what it is).

My boat is a Leopard 48. I've installed two Mastervolt 360 lithium batteries for my house and have two 12 volt 150 amp battery chargers that run off the genset and 12 volt 130 amp alternators on each engine. So theoretical charging is 560 amps at 12 volts.

I've done the following test:

1. For the master cabin, I run the air con off the genset for one hour before bed at 10 pm to cool boat to 21 C. Ambient air temp is 30-32C, humidity in the 80-90% range and water temp is 28C. Door to saloon and toilet are kept shut.

2. I keep two 12 volt fridges on all night. Stated amps from manufacturer are 4.88 + 3.6 per hour (Vitrifrigo 210 litre drawer fridge/freezer and 90 litre cockpit fridge. Other minimal use from lights as well but its not material to analysis.

3. At 10 PM turn off genset and set thermostat to 25C and turn on cabin fan. Inverter is turned on and all power comes from battery bank for 8 hours through the night. Obviously while the genset was running prior to 10 pm, it ensured that the house bank was fully charged when AC power was cut 10 pm.

4. I wake up at 6 am and turn off the air con and record amps consumed using Mastervolt Easy View.

5. For the 12000 BTU air con and 2 fridges, the DC consumed has been between 30 and 49 amps per hour. The average over the 6 nights was 37 amps per hour.

6. So I am on average using 296 amps from a 720 amp lithium battery bank to run one air con and 2 fridge units for 8 hours. This is easily recharged the next morning with a combination of motoring or genset. A lot of the discussion above failed to recognise that the air con and fridges will be cycling off frequently throughout the night. Based on my experience, I estimate that the air con and fridges are really only "ON" about 35-40% of the time.

I am very happy with the results and am now planning to add a third 360 amp lithium battery to my house bank to I can run air con in two cabins through the night.
Great information. Thank you so much. Interesting that your not using solar as well as the genset. Again thank you for that info.
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Old 02-09-2016, 13:19   #87
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Re: 12 Volt air conditioner may be availabe soon

Goingwalkabout,
We're building a sailing cat and are putting in six Sunpower panels totaling 1.8kw charging 20kw of lithium batteries (24v). Each engine has has a 2.5 kw Mastervolt 24v X 110A alternator.
We have 2 x4,000 inverters so plenty of power for our 16,000 btu air cons.
We have planned to be able to run the air cons over night without genset .
Seems like similar goals to you.


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Old 02-09-2016, 15:19   #88
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Re: 12 Volt air conditioner may be availabe soon

Solar makes a lot of sense but not for me yet. I have a young family and at this point in our lives the boat is a weekend getaway only. No long extended cruises. It's rare we are out for more then 3 days and it's never happened that we stayed put in one place for more then 24 hours straight. So engines usually in use for at least 1-2 hours a day if not more depending on wind. When we get back to the dock we have shore power.

However I have speculated that if I were to do a new build, I'd consider whether a genset is necessary. Certainly could get away with a much smaller genset at a minimum. Good alternators and solar for long term cruising might work well enough by themselves. But depends on specific circumstances obviously. Everyone will have different demands and operating conditions.


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Old 02-09-2016, 15:33   #89
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Re: 12 Volt air conditioner may be availabe soon

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Goingwalkabout,
We're building a sailing cat and are putting in six Sunpower panels totaling 1.8kw charging 20kw of lithium batteries (24v). Each engine has has a 2.5 kw Mastervolt 24v X 110A alternator.
We have 2 x4,000 inverters so plenty of power for our 16,000 btu air cons.
We have planned to be able to run the air cons over night without genset .
Seems like similar goals to you.


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Fantastic. Sounds like a great power plant. I would love to hear your operational stats. From my experience with electronics you always should make a test board to run bench tests on the theoretical design. No matter how sound the underlying theoretical design is. So your real life results of your configuration would be of tremendous value.

I would also be interested to hear what safety you have designed into your system. Such as breakers, fuses and if you're using temp gauges.

By the way, we're are you placing your solar panels? Are they going over your davits? Are you using mono or poly? Do you have any panels that regular shedding in your 1,800KW?

Best regards,
Chaya
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Old 02-09-2016, 15:37   #90
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Re: 12 Volt air conditioner may be availabe soon

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Originally Posted by OceanPlanet View Post
Excellent data! Very much what we hear from our clients about their energy management.

Although I should point out that most of the boats we set up for fast charging are 24V, which is more efficient and saves a lot of weight.
Hi, what do you use to drop the 24V down to 12V out. An invertor or another type of device.

Thanks.

Chaya
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