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Old 10-06-2016, 13:37   #1
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Question Are my batteries being used while on shore power?

I honestly haven't had the time to inspect my (new to me) boat's electrical wiring...

But, does power usually go THROUGH the batteries before going to my 110v appliances EVEN while connected to shore power?

Or, is there some sort of "battery bypass" that directly connects my 110v appliances to shore power?

It seems like batteries would get "used faster" by always draining for 110v devices instead of directly taking from the shore...
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Old 10-06-2016, 13:46   #2
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Re: Are my batteries being used while on shore power?

The shore power only goes through the batteries if the inverter is turned on . If you don't have an inverter then ignore the above. If you don't have an inverter 110v power is always direct.
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Old 10-06-2016, 14:37   #3
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Re: Are my batteries being used while on shore power?

your 110 VAC appliances are not using 12VDC power. The shore cord supplies 110VAC power. The only way to get 110VAC from the batteries is through an inverter.

If you have 110VAC available when away from the dock you have an inverter, most of those that are setup to always supply power also have an automatic transfer switch that provides power directly to the outlets, as well as a built in charger that replenishes the batteries.

the above is a little simplistic and may be incorrect to your setup.
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Old 10-06-2016, 15:02   #4
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Re: Are my batteries being used while on shore power?

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your 110 VAC appliances are not using 12VDC power. The shore cord supplies 110VAC power. The only way to get 110VAC from the batteries is through an inverter.

If you have 110VAC available when away from the dock you have an inverter, most of those that are setup to always supply power also have an automatic transfer switch that provides power directly to the outlets, as well as a built in charger that replenishes the batteries.

the above is a little simplistic and may be incorrect to your setup.
Got it. So I do have an inverter. But what you are saying is that it's probably automatically switching so it doesn't pull from the batteries when connected to A/C?

Which leads me to the question of my fridge... its a 12v marine unit... I'm guessing that ALWAYS pulls from the batteries then. I would probably be better off replacing it with a 110vAC unit to save my batteries long term huh.
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Old 10-06-2016, 15:07   #5
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Re: Are my batteries being used while on shore power?

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Originally Posted by TitoSoto View Post
Got it. So I do have an inverter. But what you are saying is that it's probably automatically switching so it doesn't pull from the batteries when connected to A/C?

Which leads me to the question of my fridge... its a 12v marine unit... I'm guessing that ALWAYS pulls from the batteries then. I would probably be better off replacing it with a 110vAC unit to save my batteries long term huh.
not at all. Your batteries are more than likely being charged while on shore power, if you plan on spending anytime away from the dock, the 12 volt unit is the way to go. Also if you're planning on being away from the dock for more than a few hours at a time you will want to know how to turn off the inverter. It draws power from the batteries even without any 110 vac appliances being turned on.
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Old 10-06-2016, 15:17   #6
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Re: Are my batteries being used while on shore power?

You can still use your batteries while plugged into shore power. Depends on if anything connected to them is switched on.

shore power runs the charger which supplies the batteries juice for the inverter. Sounds like in your case you don't need the inverter since the fridge is 12V, you need the shore power to keep the batteries charged while running the fridge and the fridge will be hooked to the batteries.

I didn't think the 110V inverter, which converters DC to AC, is directly connected to the shore power. No need to use an inverter while on shore power it's already 110V.

However, if you use the inverter it will use the batteries to give you 110V
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Old 10-06-2016, 17:45   #7
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Re: Are my batteries being used while on shore power?

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Originally Posted by Jacknast View Post

1. I didn't think the 110V inverter, which converters DC to AC, is directly connected to the shore power.

2. No need to use an inverter while on shore power it's already 110V.

3. However, if you use the inverter it will use the batteries to give you 110V
1. Unless the PO tells us what equipment he has and how it's wired, we're just guessing. He could have an I/C with an ATS or separate I and C with a manual switch.

2. Yes.

3. Not necessarily, see #1 if connected to shorepower. No need to use the inverter if connected, but it is necessary to switch to avoid having two simultaneous sources of AC power coming in. If he's not ocnnected to shorepower, then yes.

For the OP, I suggest you get a copy of Charlie Wing's Boat Electrical book.
It would be very helpful for you to read up some on how all this stuff works.
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Old 10-06-2016, 18:27   #8
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Re: Are my batteries being used while on shore power?

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1. Unless the PO tells us what equipment he has and how it's wired, we're just guessing. He could have an I/C with an ATS or separate I and C with a manual switch.

2. Yes.

3. Not necessarily, see #1 if connected to shorepower. No need to use the inverter if connected, but it is necessary to switch to avoid having two simultaneous sources of AC power coming in. If he's not ocnnected to shorepower, then yes.

For the OP, I suggest you get a copy of Charlie Wing's Boat Electrical book.
It would be very helpful for you to read up some on how all this stuff works.
So wait, the inverter then leads to the AC circuits on the ships panel, and not just the outlets on it?

Elaborate please "an I/C with an ATS or separate I and C with a manual switch.", I/C and ATS??

I'm about to start the electrical aspect of my refit is why I ask, never thought of that or if mines wired that way.
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Old 10-06-2016, 18:53   #9
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Re: Are my batteries being used while on shore power?

Assuming that your shorepower goes to an inverter/charger, the shore power won't "go through the batteries" even if all your AC devices run through the inverter. The shore power will be supplying a voltage to the batteries for charging and to everything connected to them, including the inverter. If you have some sort of monitoring system which shows Amps going into and out of the batteries, you will see very little flow regardless of what you are drawing as long as your batteries are fully charged.
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Old 10-06-2016, 19:02   #10
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Re: Are my batteries being used while on shore power?

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Originally Posted by Jacknast View Post
So wait, the inverter then leads to the AC circuits on the ships panel, and not just the outlets on it?

Elaborate please "an I/C with an ATS or separate I and C with a manual switch.", I/C and ATS??

I'm about to start the electrical aspect of my refit is why I ask, never thought of that or if mines wired that way.
It all depends on what you have and how it is wired.

I/C = combined inverter/charger, one unit in one box that does both functions, but only one at a time, of course. These usually have internal ATS (Automatic Transfer Switch) to choose AUTOMATICALLY between shorepower and inverter.

A manual TRANSFER switch is REQUIRED if you have two separate units, since you can't have two sources of AC coming into your boat operating at the same time. If you do, you get a BIG BANG!

I wrote this recently on a couple of other boating forums. I strongly suggest you do some serious reading and learning BEFORE you embark on your electrical aspect of your refit. For your own safety and the safety of those around you.

It truly gets tiresome to answer Basic Electrical questions because that's why they write books. Forums are great for specific questions, but elementary kindergarten stuff ain't one of 'em.

but electric is not my thing


WADR, this is nonsense. It's time to read up.

None of us was born an electrician. Those of us who cared about our own safety and those of our families and guests, either learned, or as others have suggested, got qualified marine electricians, to repair our boats.

Most of us learned, because when you're "out there" there aren't any tow trucks. You're on your own.

Tough love perhaps, but true.

Don't mess with sparks, they could kill you, sink your boat, start a fire and burn your boat and your neighbors' boats, too.

Sorry to be blunt, but this "elekricity is scary to me" attitude and approach is, well, truly scary to me. I see it all over internet boating forums.

There is no excuse to NOT learn this stuff. Actually, it's pretty simple.

Charlie Wing's book, Boatowners Illustrated Electrical Handbook, is a very good start for you. There is also a TON of electrical material on the internet, most of it very trustworthy, like Maine Sail's website and this: Electrical Systems 101 Electrical Systems 101
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Old 11-06-2016, 10:20   #11
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Re: Are my batteries being used while on shore power?

if you are using anything 12 vdc while on shore power...yes, your batteries are being used.
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Old 11-06-2016, 11:08   #12
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Re: Are my batteries being used while on shore power?

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Originally Posted by Stu Jackson View Post

It truly gets tiresome to answer Basic Electrical questions because that's why they write books. Forums are great for specific questions, but elementary kindergarten stuff ain't one of 'em.
MODERATOR HELP - Plz start requiring all basic, elementary forum posts are first forwarded to Stu for his review and approval!

He has made it known for quite some time on many forums he does not approve of wasting his time answering 'elementary kindergarten stuff'. Although I don't share his concern that beginners ask basic questions - I'm tired of seeing his thin patience tried time and again.

Hope this helps.

Thanks
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Old 11-06-2016, 11:46   #13
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Re: Are my batteries being used while on shore power?

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Originally Posted by TitoSoto View Post
Which leads me to the question of my fridge... its a 12v marine unit... I'm guessing that ALWAYS pulls from the batteries then. I would probably be better off replacing it with a 110vAC unit to save my batteries long term huh.

Hold that thought. If you're at the dock, connected to shore power, and your battery charger (converter) is ON... then some of that AC can be directed through the charger to your battery banks. Which can mean wear and tear on your batteries could be negligible. (Some of that can still depend on your particular set-up, but conceptually, it's a wash.)

Also conceptually, a 12V fridge running on 12V (as while at sea) can be more efficient than an AC fridge running on AC that been inverted from DC first. Might be a small difference, and again, depends.

IOW, maybe better to learn more about your system before deciding. And maybe don't sweat the small stuff in the meantime.

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Old 11-06-2016, 12:00   #14
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Re: Are my batteries being used while on shore power?

110v refrigerators are pretty rare on sailboats. Maybe there's a good reason.
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Old 11-06-2016, 12:09   #15
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Re: Are my batteries being used while on shore power?

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Originally Posted by TitoSoto View Post
I honestly haven't had the time to inspect my (new to me) boat's electrical wiring...
When you do, you will know the answer. Otherwise impossible to predict.
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