Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 03-06-2020, 16:32   #1
Registered User

Join Date: Oct 2019
Posts: 5
Summer cruising A/C and battery plans

OK, so I'm stuck in Florida for thew summer because of the virus. I'd normally go up to Chicago.
We'd love to do a couple weeklong cruises on the SW coast. We've done many of these, but this would be the first time in the summer.
Also, we much prefer to be at anchor.

Gear: I have a 400Ah Lifepo4 setup with Victron Multiplus 3000w-100A charger.
I have 400 watts of solar running through Victron mmpt controller.

Most nights at anchor, the sea breeze is fine. But in the case of rain or scorching heat, the boss would like an A/C plan.

I have a Flagship Marine 16kBtu A/C unit that will run off the battery bank (I've been testing for a few days). I also keep a Honda 2000 watt portable generator on the rail as well as a spare 2000w Chinese knock off.

Here's the rub: I hate hate hate running the generator, and I absolutely refuse to run it at night. I think it's generally just inconsiderate of other cruisers.

Now, I've been testing the A/C at the dock running on the battery. To simulate a sleeping situation, I close all vents except for the ones in the sleeping cabin. My thermostat also has a remote temp sensor that I installed in the sleeping cabin.
Using this method, I can keep the cabin very comfortable (75 degrees f) with outside being about 87 and 90% humidity. Because I have the remote temp sensor and a large A/C, the duty cycle is only 20% (10 minutes on and about 40 min off). The A/C draws about 140 amps. So 140*0.2*8 hours= 224 Ah for an overnight on the anchor running A/C.
That's a lot. But possible.

Now comes my question. I'll have to run the portable generator the next morning to make up that power. Even at a reasonable hour (11am, say), I still hate running the generator and would like to minimize the time. But the Victron charger can only put in 100 amps at once. Even if I had a zillion watt generator it wouldn't matter.

But...if I got a second charger, like the Progressive Dynamics 60 amps lithium designed charger that Battleborn and Will Prowse recommend, I could start up the OTHER generator as well and hook it up to that charger while the Victron charges from the Honda. So 2 generators and 2 chargers for a lot less charging time. And 2 generators isn't that much louder than one.

Running 2 chargers at once at least in the heavy bulk phase of charging seems like no problem to me (after all, that's what having 2 solar controllers does).

Does anyone think this is insane? I only plan on doing it once in a while, as generally I'm fine with the sea breeze, etc. But in case of heat and rain it might be nice to have the A/C option.

Thanks!
__________________

Chicagocatx2 is offline   Reply With Quote
Old 03-06-2020, 16:54   #2
Registered User
 
S/V Illusion's Avatar

Join Date: Oct 2007
Location: Lakewood Ranch, FLORIDA
Boat: Alden 50, Sarasota, Florida
Posts: 2,391
Re: Summer cruising A/C and battery plans

You can only pump into the batteries a limited amount of current per unit time. Having 100 amp charger plus a second 60 amp charger won’t change the fact your battery bank can only accept 80amp hrs max. unless you want to cook them.
__________________

S/V Illusion is offline   Reply With Quote
Old 03-06-2020, 17:19   #3
Registered User

Join Date: Oct 2019
Posts: 5
Re: Summer cruising A/C and battery plans

Thanks. I think anything up to 1C is ok for LFP batteries. In my case that would be 400 amps. I would still be well short of half that. Am I thinking about this wrong?
Chicagocatx2 is offline   Reply With Quote
Old 03-06-2020, 18:11   #4
Registered User

Join Date: Jan 2016
Location: Ventura, California, USA
Boat: Catalina 30
Posts: 631
Re: Summer cruising A/C and battery plans

While LiFePo batteries can be charged at 1
C, it's generally recommended to charge at anywhere from 0.2 to 0.5 C to increase longevity. That 0.2 C rate of course takes you to the 80 AH that Illusion mentioned.
Brewgyver is online now   Reply With Quote
Old 03-06-2020, 18:15   #5
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 30,610
Re: Summer cruising A/C and battery plans

Have you ever Summered in Fl on a boat before? It’s going to be hotter than you think
Why not go home like usual?
a64pilot is online now   Reply With Quote
Old 03-06-2020, 18:24   #6
Registered User

Join Date: Jan 2016
Location: Ventura, California, USA
Boat: Catalina 30
Posts: 631
Re: Summer cruising A/C and battery plans

There's also another potential problem with your plan. Closing most of the vents on your A/C system may reduce airflow to the point that the evaporator ices over. If this happens, it can turn ugly. As the coil starts to ice, the airflow is further reduced, leading to more icing, which can lead to premature compressor death due to slugging liquid refrigerant.

If your A/C controller doesn't have a freeze stat, you'll definitely want to add one.
Brewgyver is online now   Reply With Quote
Old 03-06-2020, 18:25   #7
Registered User

Join Date: Jan 2016
Location: Ventura, California, USA
Boat: Catalina 30
Posts: 631
Re: Summer cruising A/C and battery plans

Quote:
Originally Posted by a64pilot View Post
Have you ever Summered in Fl on a boat before? Its going to be hotter than you think
Why not go home like usual?
+1, MUCH better plan!
Brewgyver is online now   Reply With Quote
Old 03-06-2020, 18:29   #8
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 30,610
Re: Summer cruising A/C and battery plans

It’s going to take both generators anyway, one to run the AC during the day and the second to charge the battery bank. Then the hull is going to be radiating heat from the sun until almost midnight so the AC will have to run a lot harder than you think.
July and August in SW Florida is brutal, the wind goes away, and the heat catches second gear. You can tolerate it if you acclimate well in advance, but when the wind goes away, you’ll understand why no one went further South than Jeckyl Island in Ga before AC. Well that and the Malaria.

I’d guess about 5 gl of gas a day and oil changes every four days.
a64pilot is online now   Reply With Quote
Old 03-06-2020, 18:46   #9
Registered User

Join Date: Oct 2019
Posts: 5
Re: Summer cruising A/C and battery plans

64,
I hear you about going back to Chicago, but it's complicated (work, elderly parents,..)

Maybe it's just best to stay at marinas (god forbid). Anyway, I think maybe the best thing is to get out there and see how bad it is. Currently, overnight temps are in the 70s, but humidity is insane.

Brew, I do think you have a good point about potential ice on the evaporator. This is always a potential situation in Florida in the summer, even on home units.
It would have to be watched carefully. I really like the Flagship Marine A/C unit and don't want to screw it up.

Anyway, regarding the max charging current, the Victron unit has been putting about 90-100 amps into the bank when it's low and it hasn't been a problem in over a year. I float at 13.1v when at the dock, which corresponds to about 40-60% charge.
Chicagocatx2 is offline   Reply With Quote
Old 03-06-2020, 18:54   #10
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 30,610
Re: Summer cruising A/C and battery plans

I think you would be much better off with two Honda’s parallel, other wise you will have to have separate independent circuits, one for the AC and the other for the boat.
Two Honda’s paralleled will run an entire 30 amp boat, and you pretty much will need to take a 6 gl outboard fuel tank and make an extended run fuel tank with it, that way when it goes down real low you just dump a whole 5 gl can of gas into it and not be refilling the Honda’s two to three times a day.

Marina wise, find one that is Hurricane safe, and I don’t know of any down there.
a64pilot is online now   Reply With Quote
Old 04-06-2020, 00:51   #11
Registered User

Join Date: Jun 2013
Location: canada
Posts: 3,004
Re: Summer cruising A/C and battery plans

Your 2000w gen is good for an ~80a charger. You’ll need to reduce the shore amp size in the victron Setting so it charges less and does not blow the gen breakers.

So another charger does not help you. Unless you want to run both gens at once... which is nuts.

Neither of those gens should be running on a boat. For emergency use only.
smac999 is offline   Reply With Quote
Old 04-06-2020, 02:26   #12
Registered User

Join Date: Jan 2018
Posts: 2,473
Re: Summer cruising A/C and battery plans

Another little hitch that stands out to me. Very short duty cycles mean the AC won’t be able to bring down the humidity in the cabin. You’ll be cool and damp and probably moldy over time.

You either need a generator running the AC or shore power. During the day especially. At night, you could try getting by through running the generator to cool things down as you go to bed then turn it off. Or... big fans and a spray bottle.

No matter how you look at it, Florida is surprisingly uncomfortable on a boat despite it being the most popular destination in the US.
Chotu is online now   Reply With Quote
Old 04-06-2020, 07:54   #13
Registered User

Join Date: Oct 2019
Posts: 5
Re: Summer cruising A/C and battery plans

Chotu,
I think this is the best response yet. The dehumidification is a serious issue. I'd be dehumidifying the salon air, while cooling the cabin air. That's not very efficient and possibly uncomfortable. Time for more napping experiments at the dock....

Maybe I'll skip the A/C and get one of those cheap thermoelectric dehumidifiers. They're $50 and only use 25 watts.

Or stay home and order pizza...

Anyway, thanks for the help.
Chicagocatx2 is offline   Reply With Quote
Old 04-06-2020, 09:17   #14
Registered User

Join Date: Jun 2014
Location: Long Island
Boat: Tartan 37C
Posts: 102
Re: Summer cruising A/C and battery plans

following
Captain Anthony is offline   Reply With Quote
Old 04-06-2020, 10:54   #15
Registered User

Join Date: Jan 2016
Location: Ventura, California, USA
Boat: Catalina 30
Posts: 631
Re: Summer cruising A/C and battery plans

Quote:
Originally Posted by Chicagocatx2 View Post
Chotu,
Maybe I'll skip the A/C and get one of those cheap thermoelectric dehumidifiers. They're $50 and only use 25 watts.
Don't waste your money. If it only uses 25 watts, the most heat it can move is 85 BTUH. That's about one half of one percent of your A/C capacity. You'd pull more water out of the air with a few Damprid, but that's a losing battle, too.
__________________

Brewgyver is online now   Reply With Quote
Reply

Tags
battery, cruising

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
summer plans boneboy Multihull Sailboats 3 17-03-2019 16:35
2016 Summer Plans ? Peters Wet General Sailing Forum 6 27-01-2016 13:44
Pros and Cons and Various Modern Cruising Sail Plans Hugh Walker Deck hardware: Rigging, Sails & Hoisting 1 16-02-2012 06:05
Is the Summer Heat in South Florida Worse than Grand Cayman in the Summer? spencerj1961 General Sailing Forum 3 17-12-2009 05:21
Economy and Cruising Plans Keegan General Sailing Forum 20 03-10-2008 08:11

Advertise Here


All times are GMT -7. The time now is 12:17.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.