Basic Electrical for a Boat?

[Bill Seal]

Originally Posted by ttex

Amps dictate the size of the wire and the size of the breakers and or fuses. A wire rated at 10 amps needs a 10 amp fuse or breaker to protect the wire.

Amps tell you how much power your devices are drawing.

a device using 12 volt is going to draw twice as many amps as the same exact device running on 24 volts.

To get amps from Watts you just take the Watts and divide it by the voltage.

to get the Watts from amps you just take the amps and multiply it by the voltage.

A 1200 w inverter running on a 12 volt system would be pulling 100 amps at its maximum continuous. So in this situation you would have a wire or cable rated for over 100 amps with a fuse of 100 amps.

Whenever you branch off and go smaller you need a smaller fuse or breaker to protect the smaller circuit and so on and so forth.

That was my shot at simplifying electrical explanation. I hope that helps.

The "exact same " 12V device runnng on 24V will probably burn up.

[JasonS]

Definitely take the time to learn your electrical systems and engines.

Highly recommend Nigel Calders book as a reference manual. Covers almost anything you will encounter. https://amzn.to/32y5okw

Also worth getting Nigel’s Diesel engine repair book. https://amzn.to/3v5kVVf

Both are available on Amazon hardcover or Kindle. Personally I like to have the actual hard copy manuals as there are lots of photos and diagrams.

Finally, agree with the previous poster about taking the electrical class from American Power and Sailboat Squadron. Very good class. Take it with the instructor and bring your questions and boat set up to the class. The instructor can then answer specific questions you have. It’s like 8 weeks long or so and definitely will improve your knowledge.

PS. A third book I recommend is Don Casey’s Sailboat Maintenance book
https://amzn.to/3n3H5nY

These are the three books that I keep on board at all times. They are well written and address most things that a lay person can handle themselves and make good recommendations when to get help.

All three books together can be purchased for less than $115, or one hour of professional help!

Good luck!

[Lazy Jack 32]

If you plan to use an electric stove, just make sure your engine starter is on a separate battery. Would be a pity to find yourself stranded somewhere you couldn't sail out of, for the sake of electrified eggs and bacon.

[Rohan]

Originally Posted by crybllrd

how would I know how many 1000w appliances I could support with the system?

Well, if your circuit breakers trip, that's how you know your system is overloaded. Easy!

Actually I sympathize with you here, I am not an engineer and also get very confused with all the talk of watts, amps, and volts.

I'll give you one very simple rule that will help a little. Just keep in mind that the more heat a device generates, the more power it consumes. So devices that intentionally create heat like that coffee maker, hair dryer, electric stove, microwave, etc consume a hell of a lot of power (this includes air conditioning, because even though it's blowing out cold air to you, it's transferring heat into the water). So try to avoid having more than one of these devices running at the same time.

Among other items you can get an idea how much of a drain they are by the heat they generate, for example in general any laptop that gets hot and needs cooling fans (usually a gaming laptop) sucks a heck of a lot more power than your typical notebook or macbook. Tablets get much less hot than laptops, and therefore consume less power. Incandescent lights get much hotter to the touch than LEDs, and so not surprisingly, they consume more power too. You get the idea.

[Bill Seal]

Watt HOURS Watt HOURS Watt HOURS for crying out loud!!
It's like confusing MPH with MPG

[Kelkara]

Originally Posted by crybllrd

I saw that in the stickied post, but I don't see how, say, a 1000w coffee maker fits into it. If I have (for the sake of easy math) 500w of solar, 500amp battery bank, how would I know what else I can add to it? I see my (home) coffee maker says 1000w, how would I know how many 1000w appliances I could support with the system?

Since you are looking to understand Volts, Amps, Watts etc ... We can start by pointing out that you do NOT have a 500 amp (A) battery ... you have a 500 Amp Hour (Ah) battery. People often say "amp" as a shorthand for "amp hour" but since A and Ah measure two completely different things you need to understand the difference. You will also see posts where people sloppily use Watts (W) instead of Watt hours (Wh).

While you are wading though the helpful advice you get here you will also see people write amp/hour or A/h. This is a nonsense unit and means nothing. Sometimes these people use "A/h" as an incorrect notation for "Ah", but put the "/" in erroneously. Other times when people write "A/h" they understand what "/h" means but are using "A" to mean "Ah" so they actually mean "Ah/h", or just amps "A".

Considering your original question was:

I want to ask how volts, watts, and amps relate

It is unfortunate that you will get people replying with a genuine desire to be helpful, but butchering these units in a way that may confuse someone trying to understand how "volts, watts, and amps relate".


[edit] - I see sailingchirio has made my point ... a post genuinely trying to be helpful, but with Amps, Amp hours, Amps/hour, watts and watt hours all mixed up.

[Lake-Effect]

Originally Posted by crybllrd

I look to, in the future, add a small marine washer, washdown pump, and converting the stove to electric but I have no idea how to even shop for these electrical-wise.

Why an electric stove? And when/where would you use it? Ditto for a 1 kW coffee-maker.

[Rohan]

Originally Posted by Lake-Effect

Why an electric stove? And when/where would you use it? Ditto for a 1 kW coffee-maker.

Actually, electric stoves are currently becoming more popular for newer European boats.

[Lake-Effect]

Originally Posted by Rohan

Actually, electric stoves are currently becoming more popular for newer European boats.

... really? Didn't know that. Do they run off of 12v? Has all the ballast been replaced by batteries?

[wingssail]

Originally Posted by crybllrd

I saw that in the stickied post, but I don't see how, say, a 1000w coffee maker fits into it. If I have (for the sake of easy math) 500w of solar, 500amp battery bank, how would I know what else I can add to it? I see my (home) coffee maker says 1000w, how would I know how many 1000w appliances I could support with the system?

The answer to your question is actually quite simple and logical but you need a basic understanding of the concepts to even ask the question in a way which makes sense.

For example there is really no such thing as a 500amp battery. It might be 500ah (amp hours) which is really large, and at 24 volts that would be 12,000 watts. You could run about five 1000watt appliances, for a short while, before using the 50% of your 12,000 watt capacity which can be extracted.

If this does not make eminent sense, keep reading the books until it does.

[Stu Jackson]

Originally Posted by crybllrd

I hate to ask this, but after reading the stickies and lots of youtube videos, I still can't get a grasp on the electrical system.

I want to keep this from being too broad,.....................
................................

Except it is broad.

"Teach me orbital mechanics." Really?

"But don't confuse me with round things and gravity and mass..." Really?

You are asking people to make you learn. One can ask a specific question to elicit answers. But asking folks "How do I build a watch, but don't explain time or metallurgy?" is what you are doing here.

None of us was born an electrician.

We all learned.

Buy a book. Study it, reread it a few dozen times.

How'd you learn stuff at school?

[Jono as 2234]

The most useful tool i use is a Watts to Volts to Amps converter. Download free from Play Store

[ttex]

Originally Posted by Bill Seal

The "exact same " 12V device runnng on 24V will probably burn up.

You can buy device that runs on 12 volt. You can also buy the exact same device that runs on 24 volt. or you can buy the same exact device perhaps that runs on both 12 or 24 volts.

I'm sure you are aware of this. I'm certainly aware of it. Now hopefully the op is aware of it as well. I certainly wasn't very clear that's for sure.

[sailinglegend]

Originally Posted by GordMay

This will put anyone off electrickery for life.

The trouble is all books on DC for boats make the same mistake with Ohms Law on page one. It's not needed to understand the basics of choosing batteries, charging them, and monitoring their State of Charge.

[GordMay]

Originally Posted by sailinglegend

This will put anyone off electrickery for life.
The trouble is all books on DC for boats make the same mistake with Ohms Law on page one. It's not needed to understand the basics of choosing batteries, charging them, and monitoring their State of Charge.

If you don't understand Ohm's Law; you don't understand the relationships between voltage, resistance, current, and power.