Boat electrical system info

BellevilleMXZ

Petty Officer 3rd Class
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Aug 16, 2015
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85
Just trying to get my head around the electrical systems used in boats......charging system is 12v as are the batteries, thats clear of course. Is ALL the lighting 12v? I see some fridges are 12v/120v?. So what does shore power get you, just keeps batt. charged and run the A/C if equipped? What about hot water heater?
 

64osby

Admiral
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Jul 28, 2009
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6,799
Any piece of equipment that is 120 would run off shore power. If they all were 12v they would run through a inverter /converter saving the batteries when docked.

Think of it like a camper or RV.
 

Chris1956

Supreme Mariner
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Mar 25, 2004
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Cruisers can have stoves that are a combination of electric (120VAC) and alcohol. Hot water heaters can be 120VAC and run on the heat from engine cooling water. Cruisers can have things that only work on 120VAC like microwave ovens, and they can have dual voltage items like refrigerators.

AC inverters have added lots of flexibility, allowing what were shore power only devices to be used while underway, provided their current needs are modest.
 

JoLin

Vice Admiral
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Aug 18, 2007
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5,146
Typically, a boat equipped with shore power is set up like this...

12V - all interior and exterior (like cockpit lights) lighting, fresh water pump, electric head, any 12v receptacles scattered about the boat

12V or 120 V - refrigerator (switchable between the two). When it breaks, some owners replace the dual voltage reefer with a (way less expensive) 120v fridge and run it off an inverter when away from the dock.

120V - A/C, battery charger, water heater, electrical outlets, cooktop/oven
 

Silvertip

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Sep 22, 2003
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28,758
Keep in mind that inverters are not a "magic" endless source of ac power. It takes a big battery bank to run 120 vac accessories as there is a roughly 10:1 conversion factor to consider. If you have a 1 amp load at 120 vac you have a 10 amp draw on your 12 volt battery bank. Things like refers, coffee pots, hair dryers heaters, etc are all very high current draw items and would suck a battery bank dry in relatively short order.
 

H20Rat

Vice Admiral
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Mar 8, 2009
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5,199
Although any inverter you use should be marine rated, it is far more critical if you bury the inverter in a compartment somewhere. Marine inverters are spark protected, something pretty critical if you have the potential for explosive fumes.
 

JoLin

Vice Admiral
Joined
Aug 18, 2007
Messages
5,146
Keep in mind that inverters are not a "magic" endless source of ac power. It takes a big battery bank to run 120 vac accessories as there is a roughly 10:1 conversion factor to consider. If you have a 1 amp load at 120 vac you have a 10 amp draw on your 12 volt battery bank. Things like refers, coffee pots, hair dryers heaters, etc are all very high current draw items and would suck a battery bank dry in relatively short order.

Right. I can survive fine 'on the hook' for a couple days without shore power, but there's no A/C, no electric cooktop, coffee maker, electric water heater, etc. My boat's equipped with an alcohol/electric cooktop, so I use the alcohol (works fine). I carry an old-fashioned stove-top percolator to make coffee (also works fine) and I don't usually miss the A/C because at anchor the boat's pointed into the wind- get a nice breeze through the cabin with the hatches open. I turn the fridge down and mostly rely on the cooler we always carry aboard. Hot water? My water heater's plumbed into the engine- run the motor for 20-30 minutes and it's hot.

I could add an inverter but so far have chosen not to. I might add a third battery someday, but right now I'm good for as lomng as I want to be on the hook, by practicing a little power conservation. I get antsy by the third day anyway :)
 
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