Small-Boat Cruising Comforts

Soon it'll be time to cool off.....

Article by Jerry Culik

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All the comforts of home…on a boat? It’s still early in the season, and the bright sun (when we have it) and some heat would feel mighty welcome. But before too long it will be too hot and too humid to sail comfortably on the Chesapeake Bay, at least in my opinion. So let’s take a look at what’s possible when space and power are limited.

The first priority for warm weather sleeping comfort on any boat has to be getting some air moving through the cabin or cockpit tent—windows, hatches, or vents. And screens to keep out annoying biting pests, if you’re unfortunate enough to cruise where they thrive (like most of us…). Speaking of which, Thermacell devices have an excellent track record, capable of keeping mosquitos under control—even during the demanding Everglades Challenges. While the original Thermacells were powered using small butane cartridges, the latest EX55 models have rechargeable batteries and fluid reservoirs that eliminate pad changing. And they’re much more compact.

To save construction costs, many small trailersailers have fixed windows, and adding a small port or hatch in the front of the cabin can make a huge difference in improved ventilation. But if that’s not feasible (or too pricey), there are a couple of alternatives. A tried-and-true Solar Vent ($150 to $200, depending on size and features) is compact and won’t get in the way like a cowl vent can. They’re relatively bullet-proof —I have one that was built decades ago, and it’s still ticking along whenever the sun is out. The model with a 3” fan is rated at 800 cfm—and 1,000 cfm for the 4” version. Both of them can run 24 hours on a full charge. And if you’re boating in a cloudier area, the “Plus” version with a bigger battery will apparently run the fan for up to 40 hours.

For a vent that’s not solar powered—or nearly as pricey—Chesapeake Light Craft and many RV suppliers sell a Mushroom Vent that costs less than $20. It’s 5-⅝” in diameter, screened to keep out critters, and can be closed up tight—from the outside. If you want something that’s controlled from inside the cabin, a Cabin Window Vent, commonly found on small planes with acrylic side windows, lists for about $30. Rotated open, its bent shape forces air into the cabin. The 2-½” opening is rather small, but I think a bigger, sealable version would be an easy, cheap DIY project.

Besides windows and vents, a go-to solution for dealing with stagnant cabin air is a fan, and marine suppliers typically list several different makes and models on their websites. The primary differences are in the volume of air they can move, and how quietly they do it. Based on a comparison published by Practical Sailor (see Windy Ways: Practical Sailor Whips Up 12-Volt Cabin Fan Test and Fan Comparison Guide), the best-rated (and quietest?) fans seem to be made by Caframo, along with Hella, Guest, and SeaDog. Sound levels of small fans largely depend on the blade speed, and they range from 45 to 65 dB (note that a 10 dB increase is equal to doubling the sound level).

The Caframo Sirocco II ($120 at Defender), Caframo Bora ($79), and Hella Turbo ($71) appear to be comparably quiet and on the low end of the noise scale. Grill-free fans that have soft blades, such as the Caframo Ultimate ($55), are advertised as “whisper quiet” (and please post any comments on the actual performance of these and other fans in your comments!). Vornado has fans with infinitely variable blade speeds (from 150 to over 1,000 cfm). They are “DC-powered,” using a corded “brick” AC-to-DC converter, and a couple of them even have remote controls. The maximum power consumption on the smallest Vornado “Energy Smart Air Circulator” (Model 133DC, $40 on their website) is only 12 watts – you could run it from even the smallest portable power station. And its rated noise spec at low speed is a mere 30 dB. For small trailersailers not wired for 12VDC power, it’s nice to see that you can now find small “clip-on” fans with USB power plugs and wire-free rechargeable lithium batteries (e.g., USB Battery Operated Fan). Since they’re not “marine rated,” they sell for less than $15. I’ll be looking for one that can be throttled down to extend the run-time and lower the noise level while I sleep.

Small, variable speed A/C compressors were originally developed for use in EVs that, depending on ambient temperature and use, need to either heat or cool their lithium-ion batteries. As a result of that application, compact, battery-powered air conditioners are now being produced that take advantage of scaled-up production volumes. EcoFlow, probably best known for portable power stations, designed their WAVE 2 air conditioner for camping and van dwellers. It has a DC-powered compressor rated at 5,100 BTU/hr of cooling, enough for around 150 sq-ft of space – overkill for a small trailer-sailer, but nicely sized for a 20-footer. And since it has a reversible-cycle compressor, it can also produce 6,100 BTU/hr of heat. It operates on AC power or batteries, weighs 32 pounds, and lists for $1,100 (without battery), which is expensive but is still considerably less than any permanent marine A/C system. At maximum cooling the WAVE 2 draws about 450 watts; in “eco” mode, a mating 1.16 kW-hr lithium-ion battery ($600) can run it for about 8 hours. It can be operated  from any 12VDC source (such as a drop-in LFP battery) or by up to 400 watts of solar panels – but only if it has the pricey mating NMC battery installed. When throttled back in “sleep mode,” EcoFlow claims the WAVE 2 only produces 44 dB of noise, which is about as loud as “bird calls,” or a little noisier than a library, according to Comparative Examples of Noise Levels. The downside of the WAVE 2 portable A/C, besides the cost, is that it’s physically big. It has a 12”x21” footprint, so  it’s not going to fit very well on a WWPotter 15. If you’re skeptical of the WAVE 2’s performance, or want to know all the power options and run times, you can find plenty of YouTube reviews, for example:

• EcoFlow Wave 2 Solar Battery Powered Portable Air Conditioner Heater Review

• EcoFlow Wave 2 vs ZeroBreeze Mark 2: Ultimate Camping Cooling Battle!

• EcoFlow Wave 2 - Actual Runtime Testing and True Performance!? The First Portable AC & Heater!

ZeroBreeze, a tech start-up, also markets portable air conditioners. Their cooling-only Mark 2 model is rated at 2,300 BTU/hr and is sized for 25 to 40 sq-ft spaces. It weighs 16.5 lbs without the battery (half that of the EcoFlow WAVE 2) and is more compact – it has a 10”x20” footprint and takes up 28% less volume—and seems like a better fit for a trailersailer. Depending on the cooling mode, it consumes 100 to 240 watts of power and can operate from an external 24V battery (or solar panel); operating from a 12VDC source, however, will require a DC-to-DC converter to step up the voltage. The ZeroBreeze Mark 2 portable lists for $1,499 with a mating 840 W-hr battery; and $999 without.

A physically smaller—and lower cost ($900 on their website)—portable A/C unit is available from BougeRV who, as their name suggests, caters to off-grid camping folks and sells power stations, solar modules, electric coolers, and even a propane-fueled portable water heater. The Portable Air Conditioner has 2,900 BTU/hr of cooling capacity, a nice carrying handle, and weighs about 22 lbs. Since it has no internal battery, it’s tethered to either AC or 24VDC battery power.

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Permanent Marine Air Conditioning

Permanent air conditioning takes up scarce space on any boat, requires at least a gallon an hour of water to cool the refrigerant, and uses a fair amount of AC power. Most of the time it’s usable only while at a dock or if the boat has an onboard generator; and historically, these systems were cooling only. Therefore it’s extremely rare to see air conditioning on a small trailer-sailer. But changes are coming. Traditional suppliers of marine A/C – such as Webasto – have begun to sell units that can heat as well as cool – and they are now more efficient and quieter, and incorporate advanced technology, such as variable speed compressors.

Several DC-powered marine HVAC systems are now available that are more power-efficient than AC-powered systems. Mabru Power Systems, for example, sells a 5,000 BTU reversible heat pump (SCO5DC) with a two-stage compressor. It operates on 12VDC and draws 17 to 28A while in cooling mode, and a bit more when heating. That’s a pretty steep power drain, and a 100 A-hr LFP battery would provide only 3 or 4 hours of cooling (or heating). Recently, however, Archer Power Solutions introduced a small, variable-speed brushless DC compressor. It’s also rated at 5,000 BTU/hr – enough to cool a 6’x10’ cabin – and takes up only 2 cu-ft of space. The Archer units were designed to supply conditioned air to individual spaces on cruising multihulls, where a central A/C system would require lots of ducting. The efficiency of these compact, high-tech 12VDC-powered systems is very high. At home, a residential mini-split system might have an energy efficiency rating (“EER” or cooling BTUs per kilowatt of power, where higher is better) of up to 13 BTU/hr/W. The Mabru heat pump would pencil out at 15 BTU/hr/W. The Archer compressor draws a maximum of 300W (25A at 12VDC) but can throttle back to only using 30W once it reaches the temperature setpoint. With its advanced controls for the compressor and fan, it can hit an EER of over 16 BTU/hr/W. 

Compact portable DC-powered heat-pump (Archer Power Solutions and Vanlife Outfitters photos)

In Europe (and in more than half of the states), where vehicle idling more than a few minutes is restricted or illegal, truck parking coolers are now being used to cool a sleeper cab while the engine is shut off. Webasto, Dometic, Mabru, and Nomadic Cooling have DC-powered cab coolers that might be useful on a big trailer-sailer or a small cruiser with a large battery bank. Although these systems and the high-efficiency Archer system are cooling-only, more efficient heat-pump systems are on the near horizon.

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Since these portable air conditioners have ducts that attach to either the fresh or the conditioned air side, it’s possible to use a “cooler” as a “heater” by simply reversing the ducts—that is, directing the “exhaust” heat into the cabin on chilly nights. But there is a limit to how well this will work when the dewpoint is high because the evaporator (which is now handling outside air) can freeze up and will then need to be defrosted. However, small boaters still have a number of low-cost options for cabin heating. On a dock with AC power, small portable electric “ceramic” heaters are relatively cheap, available at any big box store, and they’re free of flame, carbon monoxide, and moisture. To figure out how much heater power you might want, multiply the square footage by 10 to get watts—a 1,000 watt heater can comfortably heat 100 sq-ft. And to get BTUs of heating per hour, just multiply heater watts by 3.41, e.g., 1,000 watts = 3,410 BTU/hr. At full blast, 1,000 watts could quickly overheat a small trailer-sailer, so some kind of thermostatic control to throttle back the power will be very useful.

On anchor, or without a dockside AC outlet, a propane-fueled heater like a MH4B Little Buddy Heater ($100), which is rated at 3,800 BTU/hr of heat, is probably the next best solution. Although it has automatic shut-off for low oxygen, you should still have a working carbon monoxide monitor. Running it will produce plenty of moisture that you’ve got to deal with; and you need to carry extra propane fuel cylinders. By the way, if you’re frugal and don’t want to buy the non-refillable 1-lb cylinders, you can now get legally-refillable LP cylinders ($20 at Tractor Supply).

Little Buddy propane heater and 300W 12V ceramic heater (Mr. Heater and RoadPro photos)

If you’ve invested in a cuising-sized LFP battery, using an inverter and one of those AC-powered ceramic heaters mentioned above is another option. But if you don’t want to bother with the cost and efficiency loss of the inverter, there are small 12VDC-powered heaters, mainly sold as windshield defrosters, that can work on a small boat. I found that RoadPro produces heaters that range from 150 to 300 watts. The RoadPro RPSL-581 heater-fan is compact, has a single-speed fan, draws 180 watts of power, and lists for $28 at Tractor Supply. Paired up with a 100 A-hr LFP battery, you’ll get about 6 hours of heat. Although it’s fitted with a standard 12VDC “cigarette” plug, 15 amps is probably pushing the limit of most car sockets. The 300W RoadPro RPSL-681 ceramic heater is direct-wired to the 12VDC supply and draws about 25 amps. It sells for about $43. Although it’s got two fan speeds and it can be operated in fan-only mode, neither of these heaters have a thermostat to control the cabin temperature – kind of like how heaters in cars used to work.

Tired of finding and buying ice to keep your food (and beer) cool? With the introduction of lower-cost LFP batteries, DC-powered ice-less cooler freezers are becoming more economical, and they are certainly more convenient. Dometic is probably the best-known manufacturer of marine and RV refrigerators. And while they also have portable electric coolers rated up to 99-liter capacity, there are several compact models more appropriate for small boat cruisers. The Dometic CC-32 is rated at 31 liters/33 quarts (or 39 cans, in cooler-speak) of capacity and takes up 3.1 cu-ft of space (with a 15”x23” footprint). It’s their lowest-cost portable cooler and lists for $480. It can run on both AC and 12/24VDC and draws about 60W (5A at 12VDC) of battery power. Noise is rated at 49 db.

Dometic’s smallest cooler, the CFX3-25, takes up only 2.6 cu-ft of space and has 25 liters/26 quarts (40 cans) of capacity. The bigger CFF-35 model has about the same capacity and footprint as the lower-cost CC 32 model. However, the CFX3-25 and the CFF-35 are much more power-efficient, consuming only about 12 Whr (or 1 A-hr at 12 VDC) per hour. And with a noise rating of 45 dB, they are quieter than the lower-cost CC-32 model. Most power stations would have no problem providing enough power to run these coolers; and a 100 A-hr LFP battery could run one for about four days without recharging. But low power consumption comes at a premium, and both of these coolers list for a pricey $800.

Igloo, the well-known portable cooler company, also sells electric-powered coolers. Models range from “29 cans” (20 quarts) on up. The smallest, ICF-18, has a 13”x20” footprint, takes up 2.45 cu-ft of space, and lists for $400. The ICF-32 lists for $500 and has 34 quarts (48 cans) of capacity and a 15”x 24”footprint. If that’s not big enough, there are 41, 62, and 83-quart models. All of Igloo’s ICF coolers can be powered by 12/24VDC or 100-240VAC. And like the efficient Dometic electric coolers, they draw around 1 Amp-hr (at 12VDC) or 12 Wh per hour. The noise level of these coolers ranges from 43 to 45 dB— “comparable to a light rain or quiet office space.”

Another manufacturer of portable cooler-freezers is ICECO, with models that range from 21 up to 95 quarts. The compact GO20 dual-zone model can be used as a cooler plus freezer with a 21-qt total capacity and it has a footprint of 13”x23”. Like Dometic and Igloo ICF coolers, it can operate on AC or 12/24VDC. The specs claim it uses about 430 W-hr per day (18 W-hr per hour) or about 1.5 A-hr per hour. It lists for $449. A single-zone model, the JP30, has 31-qt capacity and a footprint of 14”x23”. It lists for $499. Both of these coolers have a smartphone app for remote control. There are no specs on noise level for ICECO coolers.

In addition to their groundbreaking portable air conditioners, the EcoFlow came out with the GLACIER Refrigerator-Freezer last year. It has 38 liters (60 cans) of dual zone capacity. It has a 120W compressor that is powerful enough to make ice cubes in 10 minutes. But it’s big—the footprint is 15”x28” and it takes up 4.26 cu-ft of space. It is designed with an optional 298 W-hr plug-in battery that EcoFlow claims will run the cooler for up to 40 hours. It can also operate using AC or 12/24VDC. And if the lithium-ion battery is installed, it can run using a 240W (up to 60V or 13A) solar panel. With one plug-in battery, it lists for $1,200.

Like EcoFlow, ACOPower also sells power stations and solar panels, and they have a somewhat unique electric cooler, the LiONCooler Fridge Freezer. The 19-qt (18 liter) cooler has a 17”x27” footprint; a 29-qt model is about 5” taller. Both can be powered using an optional plug-in 193 W-hr lithium-ion battery, which looks very similar to those used for battery “jump-starters,” that can be recharged directly by a solar panel. Reviewers have measured power consumption on the 19-qt model at 150 W-hr per day; so the 193 W-hr battery can run it for more than 24 hours. It’s “whisper quiet” (measured at 45 dB, Hobotech’s review). Bundled with the battery, the list price is $598 ($398 without battery). The bigger 29-qt LiONCooler with a battery is $658. A 90W folding solar panel sized for the cooler lists for an additional $239.

While portable electric coolers are much more expensive than ones that need ice, the market is heating up (!) and competition is increasing. For example, BougeRV has a 23-qt model that lists for $200 on their website, and a taller 30-qt version for $300. The footprint is 13”x23” and they can operate from either 12/24VDC or 100-240VAC. They are very energy-efficient, using less than 0.5 amp-hour per hour at 12VDC (per Hobotech’s review) and quiet (less than 45 db). A number of other electric cooler manufacturers such as Alpicool, Anker, BODEGA, and Engel Coolers now sell coolers that operate from either AC or DC power. With the development of compact compressors and lower-cost batteries, there will be many more brands of portable electric-power coolers in the near future, and I expect that prices will continue to decrease. •SCA•