A/C from battery solar (actually realistic scenario?)

[SKMT]

My trawler already has 500w solar on aft hardtop. I have space for 1200w more on my flybridge hardtop (that I've been itching to fill).

I just installed 860ah of new lead acid gc batteries, but i have space to bump that up to 1075. On a Miami summer day, I estimate I could reasonably expect to capturre 800 amps @ 13volts (from 1700w). Way more power than I need for the usual stuff...which has me thinking about air conditioning.

Here's my idea for a summer routine. Run generator & a/c all night. Wake up in morning nice and cool with batteries fully charged. Turn off gen & a/c. With that much solar, even at 8am i will be pulling in a surplus over refrigeration & fan draws. Since I'm waking up cool I can then tolerate the heat for several hours.

Then around noon or so I wave the white flag and turn on the a/c off battery/solar. My aft cabin 10k btu claims 8-10amps, so just call that 100amps per hour @ 12v? With a 1075 ah bank, i should be able to run the a/c til 5 or 6pm. Then turn off a/c and hangout outside in the shade until bedtime, at which point i fire up the generator & a/c to run all night.

I'm trying to semi rationalize this economically. Figure over a 100 day summer, I'm saving 500-600 hours of generator. Call it $1/hr in fuel. So over 5 years I've saved $3k in fuel and 3000 gen hours. Plus additional savings captured during the other 9 months of the year, because I would literally never need to run the gen except to heat water for shower. Now i'm aware this will be at the cost of deeper cycles on the batteries (only during summer a/c use), but lead acid aren't very expensive. Also it would likely require me to get a larger inverter. And of course buy the panels, multiple controllers, and wire.

Is anybody doing anything similar? Can anybody poke holes in my summer routine plan?

[Thumbs Up]

I always wondered if you could boost efficiency by pulling the cooling water from deeper down. Of course you don't want silt but still, in most places the water near the surface is much warmer than say 8' or greater depth.

[Enyar]

Originally Posted by Thumbs Up

I always wondered if you could boost efficiency by pulling the cooling water from deeper down. Of course you don't want silt but still, in most places the water near the surface is much warmer than say 8' or greater depth.

Thats an interesting theory if you have the depth.

[smac999]

well I would never run a gen while sleeping so I’d almost do it backwards. And invert during the night. Gen early morning to boost battery bank. Then Solar recharge all day.

Your plan the solar is doing nothing untill noon since you are stating day already full.

Or move... Requiring ac at night is crazy.

[Sailmonkey]

Originally Posted by smac999

well I would never run a gen while sleeping so I’d almost do it backwards. And invert during the night. Gen early morning to boost battery bank. Then Solar recharge all day.

Your plan the solar is doing nothing untill noon since you are stating day already full.

Or move... Requiring ac at night is crazy.

And you’ve proven to have zero risk tolerance as well......so there’s that.

[smac999]

Originally Posted by Sailmonkey

And you’ve proven to have zero risk tolerance as well......so there’s that.

Boats running gens at night at anchor deserve to be shot at.

[SKMT]

Originally Posted by smac999

Boats running gens at night at anchor deserve to be shot at.

My generator is quiet...and I anchor where there are no other boats, so there's nobody to complain anyway.

[SKMT]

Originally Posted by smac999

Or move... Requiring ac at night is crazy.

I have survived 2 Miami summers without A/C. It can be done, but your life is run by the heat EVERY SINGLE DAY from June thru Sept. Sleep hot, wake up hot, then don't wanna do a damn thing all day so as to not become hotter...and repeat.

[SKMT]

Originally Posted by smac999

well I would never run a gen while sleeping so I’d almost do it backwards. And invert during the night. Gen early morning to boost battery bank. Then Solar recharge all day.

Yeah that would work if you had a 2500ah lead acid battery bank...

Or wanted to spend $15,000 on lithium...

[Pete7]

How about keeping the sun out and off the boat in the first place. My folks have a blind which allows them to see out of a large window but from the outside appears silver and reflects the sun and it works really well. Do you have sun shades up to give a cool gap between the shade and the deck or cabin top?

Pete

[SKMT]

Originally Posted by Pete7

How about keeping the sun out and off the boat in the first place. My folks have a blind which allows them to see out of a large window but from the outside appears silver and reflects the sun and it works really well. Do you have sun shades up to give a cool gap between the shade and the deck or cabin top?

Pete

I see you are in England...I don't think you understand Miami summer. Every single day is about 90-95. It's EXTREMELY HUMID. The breeze usually dies off to nothing at night and the temps only drop a handful of degrees. The water temp is 90.

I don't know how people on sailboats survive it. My trawler is wayyyy more shaded/ventilated than any sailboat. Flybridge with hardtop. Large shaded aft deck. I can "survive" outside in the shade in front of a fan with constant cool off swims mixed in. Due to the humidity/heat, the only time I spend inside the boat all summer is sleeping.

[more]

Originally Posted by SKMT

I see you are in England...I don't think you understand Miami summer. Every single day is about 90-95. It's EXTREMELY HUMID. The breeze usually dies off to nothing at night and the temps only drop a handful of degrees. The water temp is 90.

I don't know how people on sailboats survive it. My trawler is wayyyy more shaded/ventilated than any sailboat. Flybridge with hardtop. Large shaded aft deck. I can "survive" outside in the shade in front of a fan with constant cool off swims mixed in. Due to the humidity/heat, the only time I spend inside the boat all summer is sleeping.

For mi is ok to 40°C 104F in the morning before sun 86-90F is also OK But we have this 1-week heat wave in morning before sun 96-97F on sun-like Arizona 113-140F this is hot, But almost all summer I use a blanket in morning to cold 77F 25°C

[Sailmonkey]

Originally Posted by more

For mi is ok to 40°C 104F in the morning before sun 86-90F is also OK But we have this 1-week heat wave in morning before sun 96-97F on sun-like Arizona 113-140F this is hot, But almost all summer I use a blanket in morning to cold 77F 25°C

At what humidity?.

Are you OK with 40c and 95% humidity?

[more]

Originally Posted by Sailmonkey

At what humidity?.

Are you OK with 40c and 95% humidity?

No in Croatia in summer average relative humidity is 49-59%
and day wind 12-14h to 18h almost every day from 1-25 knots night wind start around 22-23 strongest in sunrise + 1 hour - 3 hour to 1-15 knots after this Now Micro-location, Micro-location and again Micro-location.
Night It is a consequence of faster cooling of the land, which causes the ground layer of air above the land to become colder than above the sea. and because we have lot mountain to shore to 1700 m is nice in night, except this 3-7 days without day-night wind

[Pete7]

Originally Posted by SKMT

I see you are in England...I don't think you understand Miami summer. Every single day is about 90-95. It's EXTREMELY HUMID. The breeze usually dies off to nothing at night and the temps only drop a handful of degrees. The water temp is 90.

The only way I would visit now is on a cruise ship. Did a spell in Belize but was young and fit back then. Strangely HK was worse with no breeze up in the New Territories.

Todays weather here is picking up and summer is coming. We are now into double figures

Pete