Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 23-08-2016, 16:19   #1
Registered User

Join Date: Aug 2016
Posts: 9
Battery Theory Correct?

Grew up on a Sailboat, looking to cruise again.....sooo I am doing my research first but am starting from a shallow baseline. I have read up a bit but wanted the opinion of some seasoned hands to see if I am tracking correctly. So I was pondering my battery set up. The following are my assumptions....always dangerous.

6 x Surrette 2 Volt 5000 Series DC Batteries each advertised at 1766 Amp hours (At $815 a Battery this is looking painful already). So I will have 12 Volt DC set up with 10,596 Amp hours available at full charge. I am hoping for a total of 1,000 Amp hour usage per day (AC, water maker fridge, freezer, electronics, water heater, lights etc.). This is of course if my math is correct, for example: (Damn it Jim, I am not an electrician!)

Air Conditioner...10 DC Amps = 1 AC Amp at 110 Volts. The Air Conditioner is a 220 Volt unit drawing 3.5 AC Amps. So 20 DC Amps through an inverter (-10% efficiency)= 1 AC Amp at 220 Volts. Meaning I need 70 DC Amps (+7 for inverter inefficiency)...So 77 DC Amps per hour to operate the 3.5 AC Amp draw at 220 volts to run the Air Conditioner. If I wish to run it for 8 hours (sleep time) then it is 8 (hours) x 77 (DC amps)= 616 Amp Hours from my 12 volt DC rig per day. If I have this correct mathematically and what not then I have a base line to start to figure out the whole system trying to keep the rest of the usage to 384 Amp hours per day max.

So if that is correct, it means I am draining my batteries to a maximum of 91% charge meaning I can get thousands (up to 5000 advertised) of recharge cycles (13 years+ plus usage). Ideally I am looking at recharge through a wind and solar combo set up 1 or 2 D400 Industrial Wind Generators and 2 160 Watt Solar Panels pushing about 15 Amps max each. I know my recharge is sun and wind dependent so I intend to monitor the entire input/output with a comprehensive Battery Monitoring System (maybe Bogart but don't know yet) to scale my amp use up and down to keep my batteries from dropping below 90% whenever possible. I live in Florida by the way so lots of sun and a bit of wind.

So here is the vexing question IF the above is correct and my research on course. Under optimal conditions a D400 and solar panels can push maybe 70-80 Amps back into the system meaning full day recharge of well over 1000 amp hours. But Solar is only 8 hours a day if lucky and wind is unpredictable....so I wont get that unless I add more power generation (trying to stay away from generators or running the engine). Can the system absorb the full amps under ideal conditions or will the charge controller limit the recharge making my 1000 Amp hour in a sailboat a bridge too far?
__________________

__________________
RichardRubright is offline   Reply With Quote
Old 23-08-2016, 16:25   #2
Registered User

Join Date: Aug 2016
Posts: 9
Re: Battery Theory Correct?

Sorry I am new here this probably belongs in the battery and solar forum, but it does form the foundation of all of my electronics decisions and limits.
__________________

__________________
RichardRubright is offline   Reply With Quote
Old 23-08-2016, 16:47   #3
Marine Service Provider

Join Date: May 2012
Location: New Orleans
Boat: We have a problem... A serious addiction issue.
Posts: 3,348
Re: Battery Theory Correct?

It's far easier to just convert everything to watts initially. But you made a citical mistake.

6 X 2v 1766 amp batteries can be hooked up to provide either 1 bank of 2v 10,596amph or 1 bank of 12v at 1766amph. When connecting batteries you can either add the voltage or the amperage not both.

But again the easy way to do this is just figure the kwh of the batteries then you can ignore everything else. So 2v*1766amp=3.5kwhx6 batteries= 21kwh.

If you use 1,000 amph at 12v that's 12kwh. Or a little more than half you batteries capacity.

The AC uses 3.5amps at 220v or .77kwh. So eight hour running it is 6kwh.

So you are planning on using roughly 18.2kwh out of a battery back that holds 21kwh. Possible, but you will be replacing your batteries twice a year. And I have no idea how you are going to recharge them every day. That's an absolutely massive amount of solar.

But there is something wrong here, well besides the above, using 1k amph/day for everything is an insain amount of power.
__________________
Greg

- If animals weren't meant to be eaten then they wouldn't be made of food.
Stumble is offline   Reply With Quote
Old 23-08-2016, 16:55   #4
Registered User

Join Date: Aug 2016
Posts: 9
Re: Battery Theory Correct?

Thank you sir! I knew the Voltage stacked so I assumed the Amp hours did the same...as I said...assumptions and dangerous. yes I figured it was off the charts insane but you have to start somewhere and I don't want to figure this out AFTER I buy a boat.


The 12KwH (1000 Amp hour at 12 Volt) was inclusive of the air conditioning. But that still puts me at close to 60% of my battery total per day....man that sucks because it is hot as hell in Florida. Perhaps I am looking at the wrong air conditioning unit. Or perhaps I should just suck it up and acclimate to where we go....the admiral won't like that!
__________________
RichardRubright is offline   Reply With Quote
Old 23-08-2016, 17:19   #5
Marine Service Provider

Join Date: May 2012
Location: New Orleans
Boat: We have a problem... A serious addiction issue.
Posts: 3,348
Re: Battery Theory Correct?

Buy a small generator. A small window unit will run very happily on a 1kw gas generator.
__________________
Greg

- If animals weren't meant to be eaten then they wouldn't be made of food.
Stumble is offline   Reply With Quote
Old 23-08-2016, 17:27   #6
Senior Cruiser
 
DeepFrz's Avatar

Cruisers Forum Supporter

Join Date: Mar 2006
Location: Winnipeg
Boat: None at this time
Posts: 7,252
Re: Battery Theory Correct?

If you want to have enjoyable air conditioning then I think it would be best to run it on a generator. You can get an auto start unit and set it for the voltage you want it to start at. That way you wont be running your batteries down so low every night.

Personally I would go with a diesel gen. Just my opinion.
__________________
The Blue Dot Campaign. This Changes Everything.
DeepFrz is offline   Reply With Quote
Old 23-08-2016, 17:35   #7
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 5,045
Re: Battery Theory Correct?

My first thought: that's almost 600kg of batteries! What sort of sailboat are you thinking about?

But anyway, let's look at your power source. 2 x 160W solar panels will give you 20 or so Amps at best and maybe 100Ah per day.

In Florida, I'd be very surprised if a D400 averaged anywhere close to 100 Watts so with two of them, let's call it 150W or 12 Amps so hopefully close to 300 Ah on a good day. So you are looking at a total energy supply of 400Ah under good conditions.

Actually, I think that is optimistic, on many days you will be lucky to get 1/3 to 1/2 that.
Your estimated 70-80 Amps is the absolute maximum you will be pushing if you are out in steady 35 knots winds at noon on a cloudless day. How many times will you see that in Florida?

With your proposed setup in your location, I'd probably budget for being able to generate 250-300Ah per day.
__________________
StuM is online now   Reply With Quote
Old 23-08-2016, 18:03   #8
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29 49.16 N 82 25.82 W
Boat: Pearson 422
Posts: 11,377
Re: Battery Theory Correct?

AC on DC (air conditioner on DC power) has been asked many times on the forum. In theory it can be done but in practice it just isn't practical. To many batteries to almost make it work. Even if you pile in enough battery power, it takes a lot longer to recharge a battery than it does to run one down so you will end up needing more solar than will fit on the boat to recharge.

I live it FL and agree, it's brutal. I've lived here off and on for over 30 years and this is by far the hottest, most uncomfortable summer I can recall. Even at night it's not exactly comfortable to sleep on board.

You need air con, you will need a generator.
__________________
The water is always bluer on the other side of the ocean.
skipmac is online now   Reply With Quote
Old 23-08-2016, 18:16   #9
Registered User

Join Date: Aug 2016
Posts: 9
Re: Battery Theory Correct?

I was afraid we would end up there. I was trying to be clever and learn....apparently you need to learn before being clever. I did find a Surrette 2 volt with 4860 amp hours...but even there (and yes where to you put the Frankenstein) I am looking at using 20% of my battery power per day with no guarantee of reasonable recharge.

As a FL resident what gen airco set up would you recommend for 48ish footer so I can start looking in the right direction?
__________________
RichardRubright is offline   Reply With Quote
Old 23-08-2016, 18:33   #10
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29 49.16 N 82 25.82 W
Boat: Pearson 422
Posts: 11,377
Re: Battery Theory Correct?

Quote:
Originally Posted by RichardRubright View Post
I was afraid we would end up there. I was trying to be clever and learn....apparently you need to learn before being clever. I did find a Surrette 2 volt with 4860 amp hours...but even there (and yes where to you put the Frankenstein) I am looking at using 20% of my battery power per day with no guarantee of reasonable recharge.

As a FL resident what gen airco set up would you recommend for 48ish footer so I can start looking in the right direction?
By the questions I assume you aren't planning to stay at a marina?

Best gen is probably the Northern Lights. Low rpm, quiet, long lasting. If you plan to run it all day, every day (or something close to that) and depend on it that would be my choice. For less constant use, small, light and less expensive the Nexgen would be my choice.

You don't want to oversize the generator so pick the size that will have the capacity to run your loads but you don't need huge extra capacity.
__________________
The water is always bluer on the other side of the ocean.
skipmac is online now   Reply With Quote
Old 23-08-2016, 18:44   #11
Registered User

Join Date: Oct 2014
Boat: Shopping
Posts: 355
Re: Battery Theory Correct?

You could go to LiFePO4 batteries (maybe double the cost of what you're estimating, but considerably lighter). They will accept a very high charge rate. You might only have to run a big gen set for a short time each day to charge the bank. Maybe a big alternator on the engine. Otherwise you need about 3 or 4kw of solar panels which you probably don't have room for (big cat?). Wind will be in the round off.
__________________
Cottontop is offline   Reply With Quote
Old 23-08-2016, 18:50   #12
Registered User

Join Date: Aug 2016
Posts: 9
Re: Battery Theory Correct?

Ok one last shot at the crazy, but this thread has me curious. Lets say theoretically you could turn the office room in an Island Packet 485 into a battery storage room (trim the port side with gear for weight compensation), and follow the sound advice above we stack 2 volt x 6 and express it as kwh...we should get 2v*4860amp=9.7kwhx6 batteries=58.2kwh total charge. The airco will use 6kwh, assuming it runs for 8 hours straight. If the batteries were full that would drain the batteries to ~89-90%. But if the airco were confined to the rear cabin alone it would not have to run all night...even at running half the night optimally we would only drain it to mid ~95%. Of course putting a seal on you cabin door probably shouldn't be done without a through examination of oxygen use in a sealed space. In the morning the AC (and other things would be running but minimally) we would be short 6kwh on the batteries and the recharge problem still exists....how many nights do you do this and how low do you want to run the batteries down. But I wouldn't think that would fry the batteries and would buy me a few days at anchorage with comfort.


yes everyone has told me what to do and I will look for the gen airco combo. But it certainly makes me wonder. 3 nights with ac at anchorage, followed by one in a slip recharging back to full could save some dough.
__________________
RichardRubright is offline   Reply With Quote
Old 23-08-2016, 19:02   #13
Registered User

Join Date: Oct 2014
Boat: Shopping
Posts: 355
Re: Battery Theory Correct?

Quote:
Originally Posted by RichardRubright View Post
Ok one last shot at the crazy, but this thread has me curious. Lets say theoretically you could turn the office room in an Island Packet 485 into a battery storage room (trim the port side with gear for weight compensation), and follow the sound advice above we stack 2 volt x 6 and express it as kwh...we should get 2v*4860amp=9.7kwhx6 batteries=58.2kwh total charge. The airco will use 6kwh, assuming it runs for 8 hours straight. If the batteries were full that would drain the batteries to ~89-90%. But if the airco were confined to the rear cabin alone it would not have to run all night...even at running half the night optimally we would only drain it to mid ~95%.
6 2v batteries at 1766 amphours each is 21kwh. It doesn't matter how you hook them up or how you think about it, it's 21kwh.

I should have mentioned that the LiFePO4 batteries can be drawn down to 20% SOC, no problem.
__________________
Cottontop is offline   Reply With Quote
Old 23-08-2016, 19:02   #14
Registered User

Join Date: Jul 2013
Location: San Diego, CA
Posts: 2,872
Re: Battery Theory Correct?

Quote:
Originally Posted by RichardRubright View Post
I was afraid we would end up there. I was trying to be clever and learn....apparently you need to learn before being clever. I did find a Surrette 2 volt with 4860 amp hours...but even there (and yes where to you put the Frankenstein) I am looking at using 20% of my battery power per day with no guarantee of reasonable recharge.

As a FL resident what gen airco set up would you recommend for 48ish footer so I can start looking in the right direction?
I usually recommend 6v golf cart batteries for those who need a lot of power. Costco or Sam's Club sells them for about $85ea, 2 of them weigh 132 lbs, will get you 220AH, and so on. At 12v, that's 2.64Kw, only 50% is usable, so 1.32Kw per pair. If you buy 10 pair, that will be 1,320 lbs of batteries and 13.2Kw of usable power. Figure $2,000 plus tax, unless you have 20 core batteries to turn in.

If you're planning something like this, I'd recommend something on the order of 2Kw of solar panels, the panels will supply the power to the A/C as well as power other 12v loads and charge the batteries. The batteries only have to get you through the night. Hopefully, the sun will rise the next morning to power and charge everything all over again.
__________________
socaldmax is offline   Reply With Quote
Old 23-08-2016, 19:05   #15
Registered User

Join Date: Jul 2016
Posts: 641
Re: Battery Theory Correct?

Why the focus on battery power instead of a simple genset? Some folks have two AC units, one smaller for while at sea powered by a small genset. Larger BTU unit for marina. Batteries are amazing these days, but get enough sized to met your boat essential equipment and food refrigeration/water making - that's within the capabilities of solar and wind. AC=genset.
__________________

__________________
SV DestinyAscen is offline   Reply With Quote
Reply

Tags
battery

Thread Tools
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
Battery Bank Wiring. Is this Correct? Hoohaa Electrical: Batteries, Generators & Solar 18 22-07-2014 21:55
Battery Theory nolandinsight Electrical: Batteries, Generators & Solar 9 14-07-2013 15:51
Loaded battery voltage. What's correct? MarkJ Electrical: Batteries, Generators & Solar 5 05-01-2013 10:15
Correct Bowthruster Battery System Sulaire Electrical: Batteries, Generators & Solar 16 14-02-2012 15:27
Correct Connection for 4-Way Battery Switch anglooff Electrical: Batteries, Generators & Solar 4 11-06-2010 09:55


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 07:05.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.