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Sailboat Size vs LFP Capacity

svHope

New Member
Joined
Nov 28, 2019
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23
Hello,

I wanted to take an informal survey for those who have LFP systems on their boat. What is the size of your boat and what is your daily energy consumption (either aH per 24 hours, please indicate your battery voltage or kWH per day)? Also a couple other comments if you know: consumption at anchor? underway during day and or night?

I would like to know that I build a system that will really cover our needs, especially a desire to sail overnight with out running the generator.

thanks for any of your comments.
 
38' Mono. I use (while cruising) about 100Ah@12V per day. I just upgraded from 230Ah of FLA to 300Ah of Lithium. I also just upgraded from 420W of solar to 670W.
But this really won't help you. You need to measure YOUR usage. Things like refrigeration and Auto pilot could make a very large difference between otherwise similar seeming boats. I have a only small cooler, no freezer, and no autopilot.(I use a monitor windvane)
 
Also a couple other comments if you know: consumption at anchor? underway during day and or night?
This will depend on your setup, and what the loads are under different conditions. If you have solar or wind power how much and in what part of the world. Your sail boat should have instrumentation to monitor power consumption.

I suggest you carry out your own tests, I am surprised you have not already carried out an appraisal of your system under different situations.

For what its worth, on my ocean crossing on a 45 ft ketch, 500Ah lead deep cycle battery pack. Electric autopilot on continually, high efficiency refrigeration (6 to 8 inch insulation). Used about 100Ah per day, batteries recharged by auxiliary engine high output alternator, 1 hour each day.
Solar panels only deployed at anchor, solar plus modest wind power provided all electrical demands.
There were no high power consumers like water maker, microwave.

One thing I can guarantee, is that the more complex your electrical system, the more time and money you will need to maintain and repair, especially the generator.

Mike
 
Agreed on the above suggestions. Unfortunately we came back to the states in Dec 2019 from our boat in Panama and had a major life change surprise. For the last year plus I have been getting treated for stage 4 cancer. My cancer is now in remission and we hope to return to our boat late June or July 2021 for a few months before returning for follow up tests and scans. Cancer and Covid has kept us here in the states and we were not prepared to design our system. Since January I have been experimenting and teaching myself about LFP by making a small 20aH DIY battery. I am currently building my second 20aH battery.
We have a 49 ft cutter and have many major systems aboard. The current house battery set up is with 940 aH of golf cart trojans in a 12 volt format. My plan is to fit 800 aH of LFP but could possibly fit more, although another factor is that we have 8D battery boxes in 4 locations on the boat. Our solar will need to be upgraded from the current 630 watts to as much as I can comfortably add.
I am just hoping to get some real world data vs my guestimates of our usage from afar.
Thank you for your comments.
 
I've just installed 1120ah of lifepo4 and have a 250ah 8D as a starter/backup. I've got 620w of solar now with plans to upgrade to about 1500w. We live on our 44ft monohull. Someday I'll have electric watermaker and instant hot water heater and maybe some AC and we also have an electric autopilot. We spend a fair amount of time working/using computers and tvs etc in the off season and while at dock for normal life and I wanted a system with lots of headroom for future expansion and the many cloudy rainy days we get in the PNW.
 
I think you need to make a list of what you want to run and how much you are going to be at sea. You comment that you can't design a system is troubling to me. If you can't design it you likely wont be able to trouble shoot it.(though you certainly sound smart enough) This is a big deal at sea. If you are staying local then that is fine but if you are planning multi day crossings you should be able to completely trouble shoot things.

Practice on your current residents and get a Kill-a-watt meter and measure power draw on what you use daily around the house. Some utilities also offer live and stored data of your house usage. You also got to pay attention to who is living on board, are they going to be able to conserve energy and not be wasteful....I follow my wife around turning off lights constantly, but after thinking about this I am going to start telling her to turn off the dam light we are practicing for sailing.....we have got our current house down to a constant 900 watts draw with 7 people living there and a large 7000 sqft house. My wife is the worst offender.

Wish I had time to sail more and envy you on your adventure and wish the greatest luck to you. I think your biggest draw is going to be heat or AC if you are going to need it.
 
At anchor we use about 24Ah per day (front-opening fridge, lighting, music, charging devices, electric WC etc., whereas when sailing we use about 150Ah per day (above loads plus chartplotter, instruments, VHF, AIS transponder, autopilot, navigation lights etc.). On-board diesel heating adds about 40Ah per day to the above figures if used (basically running the air distribution fans). We don’t have air-conditioning as it never gets that hot boating in the UK …
 
Forgot to mention that ours is a 30ft sailing boat and the battery is 12V. Incidentally, a simple way of estimating solar panel daily output is to take the panel’s rated power and multiply by 25% i.e. a 100W panel is capable of producing about 25Ah per day. This approximation actually worked out pretty much as measured for our panel, but do bear in mind that this is a very rough way of specifying solar panel output and that there are other much more accurate approaches….
 
On our 38 ft sail, 12v system I replaced our 386 ah gel house batteries with a 280ah, Eve LFP DIY pack. It has worked well. More than enough capacity for our coastal cruising. ( fridge, anchor light, vhf, radar, autopilot, chartplotter, windlass, power halyard winch, 100w solar, ...). The really noticeable difference is the behavior with incidental engine charging ( in/out of harbor, windlass use,..), previously the gel would take very little charge with these uses but the LFP can really charge efficiently by taking in as many amps as I choose to send it ( dc-dc victron). It is a little hard to estimate the daily use with the interleaved charge and discharge, I believe about 80-90 ah.
 
30ft motorboat. 1690ah 12V LifePo4. 1300 watts solar
and per day use is 2,7-2,8 KW
You've got a lot of power there and it doesn't look like you're using that much of it, you must have future upgrade plans to add some aircon or something?
 
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