Overnight Cooling Without Shore Power

[Delezynski]

Good talk about batteries.
*** BUT ***
The actual center of the topic of anchoring out in heat is where are you cruising!!!
We sailed on lakes, and in California for years and never needed any overnight cooling.
We cruised the Sea of Cortez in the summer! We anchored out for months, not just overnight. Air temp over 110 deg F and water temp OVER 95 deg F!!! Over night was torture, hot & sweaty. Each of us had a fan and that was only a bit of help.


One thing I did was make a wash down pump that used a hose over the side for it's pickup. That hose, with a weight on it, would drop 10 ~ 15 feet deep for pickup. Below the normal thermocline for cooler (Apx. 85 Deg.) water and just after sunset was use the wash down pump to wet down the deck. Between the cooler water to start and evap cooling we could be good for a few hours.


Now, we purchased a small A/C unit (Zero Breeze) that has it's own battery. It does not last ALL night and does not make our small cabin (Nor'Sea 27) cold, but it sure helps a LOT!!!


Good luck and know that with or without it's SO WORTH CASTING OFF THE DOCK LINES!

[sailor1026]

@SailingKate We have a 560Ah LFP battery bank with Victron Multiplus 3K. We can run one Dometic 16KBTU aircon unit continuously for about 4 hours on the battery/inverter. A soft-start system would help it start. We can extend the run time by setting the temperature so that the aircon compressor runs intermittently.
In practice, reducing humidity is the primary factor. Running the aircon for about 2 hours prior to going to sleep is generally sufficient. About 2 in the morning, it gets stuffy and we open hatches. We use a fan to help stay cool. We can do this with the batteries or genset. I recommend a larger capacity battery bank for regular over-night operation. Of course, this depends on the aircon unit's power requirements and other house loads like refrigeration.
Our LFP battery bank is built from CALB 180 cells, 4P4S, with a HousePower BMS. Details at svlux.blogspot.com with references to additional reading materials.

[wingssail]

We have lived aboard in the tropics for 15 years.

We carry an 8000BTU air cond which we only use when on shore power.

For periods at anchor we rely mainly on shade (day time) and fans. We have 7 installed Hella Turbo fans (and a few spares). You cannot get more than 48" from a fan on our boat.

For those unusually hot nights in desert areas (like Sea of Cortez) or totally humid places such as near the equator we have this emergency hack: A small spray bottle with fresh water is kept on the table next to our bunk. When we can't get to sleep due to the torrid or sweaty heat we spray ourselves and let the nearby fan cool us down.

Guess it is not something you want to rely on for months at a time, but in emergency situations, it works.

Batteries: We have used LA batteries for 34 years including several years anchoring in the tropics with no or very rare shore power connections, so we relied on daily cycles of the batteries. Our Trojans lasted 5-7 years so that is probably over 1000 cycles. At $160 per battery (we use four) this is a lot cheaper than LFP over the life cycle, not to mention the BMS and charging systems needed or the issues when trying to maintain or repair these management systems in remote places, if they ever failed, which they probably will do eventually.

[Colin A]

Something I have seen done in the past is having a smaller AC to run off batteries and cool a small area overnight. I know years ago i made a setup for a customer with a 5200 BTU mermaid to do it. And now there are some even smaller units that might work.

[reflectionsv37]

I'm in SE Asia and this time of the year it is extremely uncomfortable. The temperatures and humidity can make it almost unbearable.

I have a Honda 2000 watt generator and a 5000BTU window A/C unit I set in the companionway. The Honda easily runs that AC unit. It runs at just above an idle and will run about 10 hours on a tank of fuel or slightly less than a gallon. I've purchased a special cap and connected the generator fuel to a 5 gallon external tank. It can run the AC unit non-stop for about 2 1/2 days. A friend has the same generator and told me he can run two 8000BTU AC units but I'd suspect it will be running at considerably more than near idle. Ideally I'd like a built in AC unit so I didn't have to deal with moving a window AC unit around.

The generator is stowed in a custom built frame attached to the stern pulpit so there is no heat below and can barely be heard when down below. We always try to anchor away from other boats so we don't bother anyone but the Honda generators make very little noise, particular at idle or very low settings.

Everyone should have a Honda generator aboard. It can run my onboard 75amp battery charge at full output. And is always available for AC power. And, they are extremely reliable. It will be one of the best $1000 purchases you will ever make.

I can't imagine trying to run an AC unit off of an inverter. You would need a massive battery bank, an inverter with enough power to handle the startup of the AC unit and then you'd have to recharge that massive bank.

I sleep really well now!

[RELENTLESS 1]

I didn't see anybody mention ChiliPads - a couple of fellow owners swear by them. They are a colling pad/electric warming pad that you sleep on and use minimal power to run - it won't cool the cabin but it will cool you and yours all night long as you sleep.

[JBP]

If you are thinking of pulling sea water through a radiator with a small pump and a small fan, I think it's brilliant. I've often thought to try it. I have no shore power, no generator, no massive batteries but still would like something more than just a fan.

[rslifkin]

Originally Posted by JBP

If you are thinking of pulling sea water through a radiator with a small pump and a small fan, I think it's brilliant. I've often thought to try it. I have no shore power, no generator, no massive batteries but still would like something more than just a fan.

Not a bad idea at all. Ideally with a long hose for intake so it can be dropped down 15 - 20 feet (when in deep enough water) to draw from typically-cooler water well below the surface.

[Muaddib1116]

Originally Posted by RELENTLESS 1

I didn't see anybody mention ChiliPads - a couple of fellow owners swear by them. They are a colling pad/electric warming pad that you sleep on and use minimal power to run - it won't cool the cabin but it will cool you and yours all night long as you sleep.

I had never heard of those, they look pretty neat. They have a pretty low watt use too. This with some fans might be a pretty great, low power alternative to ac.

[wingssail]

Originally Posted by Colin A

Something I have seen done in the past is having a smaller AC to run off batteries and cool a small area overnight. I know years ago i made a setup for a customer with a 5200 BTU mermaid to do it. And now there are some even smaller units that might work.

Sounds doubtful.

"Startup wattage for any new 5000 BTU AC will surge to 1200 watts to 1500 watts momentarily, and will average 900-1000 watts typically whenever its compressor kicks on (www.fiberglassrv.com › forums › 5000-btu-air-conditioner-and-1000-w...)"

That seems high to me, my 8000 unit is rated at 770 watts.

So, lets say 600 watts for a small unit. That is, when the compressor is running, say 50% of the time. Over night, (8 hours), that is 4 hours x 600 =2400 watts. At 12 volts that is 50 amps per hour of operation with compressor, somewhat less with the fan only. Total=250amp hours, per night. Not counting inverter conversion and start-up amps.

Can your batteries take that? What do you use to recharge them each day?

Maybe, but that is high duty cycling.

[ferrofan]

thought about evaporative cooling? big metal tray designed to be suspended inside the open hatch fill it with water and as the breeze blows over it, it wil evaporate and cool the air passing in to the cabin. very Heath Robinson but possibly worth trying it for S's & G's. It's never going to be air con cool but will lower the temperature a tad.

[Zhyachts]

Use a "Cooling Blanket". A damp bath towel laid on your body with a fan blowing on it. It works.

[MVDarlin]

I've had an idea to run a 20ft hose overboard with a weight to a lower dept with cooler water than surface to a bus heater radiator with a fan. Only concern is how big of a pump do I need. I plan to test a small 1 gpm pump this year. I guess the lift is only from water surface to the port light, about 4 ft. If I can get a 10* temp drop that should be sufficient.

[RELENTLESS 1]

A damp towel sounds exceedingly uncomfortable - especially when it dries - vs a pad this is cooled.

[Tupaia]

Originally Posted by MVDarlin

I've had an idea to run a 20ft hose overboard with a weight to a lower dept with cooler water than surface to a bus heater radiator with a fan. Only concern is how big of a pump do I need. I plan to test a small 1 gpm pump this year. I guess the lift is only from water surface to the port light, about 4 ft. If I can get a 10* temp drop that should be sufficient.

If the end of the return line goes back into the water and it is a closed system then the pump simply need to circulate sufficient volume and over come the friction.

There is a whole raft of information about temperature gradients in the near surface layer. Since the surface water temperature is nearly always hotter than the atmospheric temp you will need a very long pipe.