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Old 09-07-2024, 14:54   #1
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Liveaboard power requirements

I am purchasing a koopmans 38 with 300watt of Solar and 3 x 110ah house batteries. This will give me around 330ah with roughly 155ah usable - that translates into about 2000watts. I am upgrading the solar to 600watts to ensure I can recharge the bank in around 3hours (depending on the day and conditions)

Cooking and water heating are done by gas.

12V TV is around 80watts
starlink averages about 80watts
LED lights - 10watts each (say 5 on at a time) - 50watts
phone/laptop use - 50watts

That totals around 260watts of use per hour. Realistically the TV,laptop use etc won't be on permanently so if I average it out to 200watts I should be able to go 10hours before needing a recharge. Usage will mostly be during the evenings and I am off the boat at work from 7 to 6 daily (except weekends)

Keen to hear others power use and pitfalls so I can plan accordingly.

I am planning to upgrade the battery bank to a LiFePO4 to get more usable energy per battery but that's next years project.

EDIT: to add, the motor has a 100A alternator installed so in worse case scenarios i can run the motor for a bit to recharge the bank.
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Old 09-07-2024, 19:52   #2
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Re: Liveaboard power requirements

Hi There Buddy

I am a solar independent single handed world cruiser. I am currently in Whangarei, New Zealand.
After many years of cruising I can say that the main power crushe is not electrically based. It’s insulation around your refrigerator/freezer. I redid my box twice before I got it right. The 1st time was messed up because all that was available was white pellet styrofoam in Mazatlan, MX 25 years ago. Is absorbs moisture and has a low R value. I did post a thread a few years back with load and engineering spread sheets that are very valuable in building out the box correctly o eliminate all 3 types of heat transfer.
LED lights make a big different INCLUDING NAVIGATION & Anchor lights
Gas cooking helps a lot and a pressure cooker is definitely a game changer.
Starlink eats a lot of power and should be only on when using it.
I use a Raspberry Pi and opencpn/plotter for navigation screen sharing to an iPad Air in the cockpit over the pi’s integral WiFi access point ( Openplotter feature). It uses .4 amps@ 12v.
I use a my radar is a B&G halo 20+ and will overlay radar.
I have 400 amphrs of usable firefly batteries and 400 wattts of solar.
My batteries are full at anchor by 10am
Underway by 12pm, if I’m using radar at night they are are full by 1-2pm.
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Old 09-07-2024, 20:01   #3
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Re: Liveaboard power requirements

600 Watts of solar may be enough but 150Ah of usable battery capacity sounds pretty light. Refrigeration uses a fair amount of power, particularly in warm climates. We might use 150 Ah overnight for the refrigerator, freezer, lights, fans, several hours of Starlink and a cycle of the Instant Pot.

If you run an autopilot on passage that could exhaust your battery capacity overnight for just that use. While not necessarily intuitive being on passage under sail is our worst case energy usage scenario. A couple days of cloudy weather can be very hard on the energy budget also....
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Old 09-07-2024, 20:20   #4
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Re: Liveaboard power requirements

Originally Posted by akopac View Post
After many years of cruising I can say that the main power crushe is not electrically based. Itís insulation around your refrigerator/freezer.

Amen, we have a winner.
It was true decades ago, it's still true today.
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Old 09-07-2024, 22:45   #5
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Re: Liveaboard power requirements

I had a single 100w solar panel and 2x100ah house bank batteries +1 engine 100ah . They ran 2x 12v fridges (built-in and a large portable), LED lights, pumps, radio, etc. Never ran out of power in California. But I also don't leave anything except fridges running 24/7. Both fridges were not nearly as well insulated as on most quality boats. Just pointing out that it's really your usage that maters.

I would suggest upgrading batteries before upgrading solar. They give you more capacity to store what solar produces. Remember that everything is fed by batteries, solar just charges them. As long as they are topped off by the end of the day and ready for the night - you are good to go.
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Old 10-07-2024, 02:34   #6

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Re: Liveaboard power requirements

Using the newish "Flat" orientation setting on Starlink reduces the power considerably.
80Watts seems a lot for a 12v TV what size is it.
You don't mention a fridge or a freezer these are typically large consumers.
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Old 10-07-2024, 04:52   #7
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Re: Liveaboard power requirements


Keen to hear others power use and pitfalls so I can plan accordingly.

From my experience full time cruising you can expect to use 150-200ah/day and your current solar will probably do around 100ah/day. But if you are only on the boat on weekends your load drops to only the frig/freezer and during the week the solar will mostly check up (long as as you turn off the SL). I operated for years of weekend use ad 2 years full time with a 290W panel before increasing to 640W.
Don't ask a bunch of unknown forum people if it is OK to do something on YOUR boat. It is your boat, do what you want!
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Old 10-07-2024, 08:49   #8
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Re: Liveaboard power requirements

Since you said liveaboard, the power consumption will be similar to what you use at home if you want to have a quality experience and not constantly monitoring your battery meter and turning off lights and appliances. Coffee machine, icemaker, washing machine... even a clothes dryer. Nothing beats the experience of fresh, dry towels and sheets. These appliances use a lot of power in addition to the fridge. I do not think it is practical to power all of this with solar. I run a 48 ft powerboat with minimal batteries (3 kWh) but I do run the generator when needed at anchor. I estimate daily consumption around 9 kWh including water heater and cooking. You just can't get this from solar/batteries.
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