Originally Posted by Ex-Calif
Once you have the equipment
it doesn't with many caveats.
Therre are many boat skills and when you get to "cruising" level one skill that I think is vitally important is DC electrics skills followed by ac electrics skills. This is because when you pull the plug
you become and island and much of what we deem as comfort becomes a power management exercise.
Time over time people have posted how to make a DC power budget
. It is not rocket science at all and very simple to do. Once you do a power budget you must simply make a system that supplies that budget day in and day out. If you used 20 amps an hour all day every day with no variation one solution would be a generator
producing 20 amps an hour. Theoretically you wouldn't need batteries.
But no one runs everything all day every day. Everything has a duty cycle, lights at night, pumps when they cycle, nav eqiupment underway but not parked, even the fridge is not running all the time.
So you get an average daily consumption
. Now you need a charging
system that supplies this average over time. How much time? That's where a battery
Lets say my average is 100 amps a day. If I install 200ah battery
usable capacity I could not charge them for 2 days. But at the end of that 2 days I better be generating power and on average I better be generating 100 amps a day. So at the end of this two days I have a 200 amp deficit. In the next two days I better generate 400 amps, and so on...
How you charge has options. The engine alternator
, towed generators and gensets. Nuclear power has not yet reached pleasure boating
Each generating source has benefits and drawbacks. So multiple generating sources are usually desirable. However in most all cases where high power items are desired, aircon, refrigeration, electric propulsion
, electric heating
of water and cabin
, cruisers flock to the genset. 2-3kva seems the sweet spot.
The fridge is probably not the holy grail of pleasure boating. It is probably aircon or electric propulsion
So the original question. A fridge generally draws 4 amps on a 50% duty cycle. If you want one you simply have to generate 48-50 (4x24x.5) amps of power for it, every day.
to generate 50 amps is readily available but not cheap
. A failure of a charger
power controller could consume several months of the $500 a month sailors total budget to fix.
One reesson battery banks are sized the way they are is to allow some set time between need to charge. A system reliant totally on solar as a minimum must serve the needs overnight as solar wont charge at night. Also in many places the sun doesnt shine every day and there is seasonal variation on how much energy can be harvested from a given array.
So anytime someone says, "I'd like to add XYZ electrical service
to my boat" there are rreally only two questions. Can you generate its daily consumption
and does the daily consumption impact your "mean time between mandatory charging" based on the current
battery bank size.
The reason the 2-3kva generator
is the magic is because it generally will supply enough power to run anything the boater wants as long as it is running - i.e. aircon - without consideration of the need to store the power for this utmost of power hungry services.
Why is it everyone leaves out the most important cheapest thing to power consumption bliss? If you have the capacity to begin with you have already gotten ahead of the game
The best way NOT to drain your batteries is have as many as you can carry.
Two house batteries is a joke. You need at least four very good (not the best) batteries for the house lights and electronics
alone. Once you have these then you need to top them off regularly. Wind
, Solar, and a portable generator come to mind. Also I have more then a few solar lights that last all night on my deck
in strategic places so other boats can see me and I'm at a dock
right now. Still solar lights are the bomb (just use good rechargeable batteries in them) and I'm thinking of getting green and red lenses for the obvious reasons.
Also if you need hot water then use the sun. Many have said on a sunny day you can heat water in a solar shower
in 1/2 hour. use it to wash or shower
Why not buy a cooler that plugs into a lighter to keep things cool not frozen but cool? A lot less consumption there and the price
is under 100 USD on line.
There are ways to do it but you have to think outside the box and have a plan and a method to get there before you are cruising.
I just went and spent 54 dollars for food
this week. That's enough to make two weeks of meals
on my boat. The most expensive thing was the meat in cans. But canned vegis are cheap, really cheap and can be added to food
to help it out. But once it is opened then you need to put it away to keep it cool for the next meal in the morning. Go over seas and they don't get out the cereal and milk for Breakfast they eat things that you and I wouldn't even think of.
Ex-Calif you know because your in Asia
. When I was in China
breakfast was really no different then dinner. Maybe more rice or dumplings that's all. In the morning grab the open can of vegi's and a couple eggs with condensed milk and make a omelet if you want but it's all right there in your cooler. I've seen Chinese people order fish
P.S. They also go to the market every night for dinner so there vegi's are as fresh as they can get.
Here's a good example I hope the link works.
12 Volt Snackmaster Deluxe Family Size Cooler/Warmer RPSF5235 - $82.59 :