Run both 120 & 12v electrical - Fiberglass RV


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Old 07-30-2013, 07:33 PM   #1
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Run both 120 & 12v electrical

Has anyone devised a way to run all electrical items off of shore power when available and then switch to 12v battery when needed? Does it have to be half 12v and half shore power? Also does anyone have a wiring diagram for a 76 scamp? The diagram in the documents section of this site is for a newer scamp with AC, brakes and all sorts of different things.
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Old 07-30-2013, 11:21 PM   #2
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You need an inverter/charger. Convert AC to DC when on shore power, and then convert DC to AC when on battery power.

I run everything that I can on 12V - I worry a lot more about efficiency when I'm on battery then when I am connected to unlimited power!

I can run everything but the air conditioner and the microwave off of battery, I need to start the genset or be on shore power to use them.
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Old 07-31-2013, 07:38 AM   #3
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I think Jon is confusing an inverter with a converter. An inverter converts 12v to 120v whereas a converter does the opposite. You need a converter. Everything in your trailer should be 12v except for the outlets and microwave and air conditioning. Thus plugging in at a cg will allow you to use their electric and convert to 12v to operate your trailer and charge your battery. Once you unplug, your battery will provide the needed power for everything. See here for details The 12volt Side of Life (Part 1).
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Old 07-31-2013, 07:42 AM   #4
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If it was me, I would run everything I could straight 12v, then just wire an inverter in for only what had to be a/c.

Really, there are very few things you will be able to run on ac with an inverter, anyway. Two batteries will help, but you're still going to be limited to laptops, etc. also, many "ac" things have power supplies that convert them to dc, so look at that also. Much better to run them straight from dc than go dc-ac-dc again.
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Old 07-31-2013, 08:42 AM   #5
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Jon is describing an inverter/charger that is used on some high end RVs. It acts as a converter when plugged into AC, providing charging for the battery & 12V for the trailer, and switches to an inverter when 120V AC isn't available, producing 120V from the battery. Of course you need enough battery to make it practical, which might be a problem if you want to power high wattage appliances...

An Example - A Xantrex Freedom 458.
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Old 07-31-2013, 09:11 AM   #6
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Quote:
Originally Posted by cpaharley2008 View Post
I think Jon is confusing an inverter with a converter. An inverter converts 12v to 120v whereas a converter does the opposite. You need a converter. Everything in your trailer should be 12v except for the outlets and microwave and air conditioning. Thus plugging in at a cg will allow you to use their electric and convert to 12v to operate your trailer and charge your battery. Once you unplug, your battery will provide the needed power for everything. See here for details The 12volt Side of Life (Part 1).
No confusion, I promise that an inverter/charger is a real device! I run a Xantrex RS3000 that is a combo 3000 Watt sine wave inverter and a 3 stage charger. I keep my Bigfoot plugged in to shore power at home to keep the batteries charged and also keep the humidity down in these hot summer months in NC.

Regardless of what you use to convert DC to AC, check to see if you need a true sine wave inverter. The cheaper models tend to be square wave or modified sine wave, which causes problems with some electronics and most microwaves.

There was a good recent discussion of the options on expo - http://www.expeditionportal.com/foru...-batt-charger?
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Old 07-31-2013, 10:13 AM   #7
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Well, I don't have A/C or a microwave so that shouldn't really be a problem. All I really need are a few interior LED lights, the heater, water pump and one outlet for charging cell phones and other small electronics.
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Old 07-31-2013, 10:36 AM   #8
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Well, I don't have A/C or a microwave so that shouldn't really be a problem. All I really need are a few interior LED lights, the heater, water pump and one outlet for charging cell phones and other small electronics.
The led lights should be 12 volt, the water pump is 12 v, your phones should charge on 12v, and if by heater you mean furnace, that's 12 volt. If you meant electric heater, you aren't running that off an inverter, anyway.
Unless I've missed something, you shouldn't need an inverter for anything listed. A laptop might be a different story, depending on required voltage.
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Old 07-31-2013, 10:48 AM   #9
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You are correct Jared and and that is why I was trying to clear up the usage of inverter and converter in the above posts, which may lead to confusion to others.
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Old 07-31-2013, 10:49 AM   #10
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Originally Posted by Jared J View Post
The led lights should be 12 volt, the water pump is 12 v, your phones should charge on 12v, and if by heater you mean furnace, that's 12 volt. If you meant electric heater, you aren't running that off an inverter, anyway.
Unless I've missed something, you shouldn't need an inverter for anything listed. A laptop might be a different story, depending on required voltage.
I agree, I'm not sure why the OP wants to make AC. Just run everything off of DC and use shore power to charge/float the battery bank when available.

For charging phones, etc just use 12V (automotive) adapters instead of 120V household adapters and should be good to go.
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Old 07-31-2013, 11:40 AM   #11
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12 vdc & 120 vac ???

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Originally Posted by jimkill View Post
Has anyone devised a way to run all electrical items off of shore power when available and then switch to 12v battery when needed? Does it have to be half 12v and half shore power? Also does anyone have a wiring diagram for a 76 scamp? The diagram in the documents section of this site is for a newer scamp with AC, brakes and all sorts of different things.

First and foremost, ferget what's already there. Any schematic you might find has, after 30+ years, almost no chance of matching what you have thanks to the efforts of how many previous owners. I say it's best to start fresh with new wires and not go through the hassle of damaged wires and loose connections etc. I just did this with my Hunter Compact-II and got rid of all kinds of problems.

A good start for your system would be a Progressive Dynamics PD-4045 power chassis. This will give you all new a/c distribution, a 45 amp DC converter with a 12 circuit fuse panel and a smart charger for the coach battery.

After that, if you need AC power when not plugged in (for What?, give us a list) you can add in a DC to AC inverter.

Then, when you are without ac, all the DC stuff will run off of the battery and when you lug in your 120 VAC outlets etc. will work and the DC will run off of the converter while it's also recharging the battery.
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Old 07-31-2013, 11:51 AM   #12
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Thanks for the replies and sorry for the confusion. I had no idea how the scamp system was supposed to work, I didn't even know that shore charged the battery. My question stemmed from the fact that my trailer has some lights that only work on shore and some that only work on battery. What I'm going to do is make everything run off 12v battery and have the shore power just charge the battery when hooked up. Then I'll get a small DC to AC inverter so that I can have an outlet just in case. That will do everything I want to do.
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Old 07-31-2013, 12:36 PM   #13
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Originally Posted by jimkill View Post
Thanks for the replies and sorry for the confusion. I had no idea how the scamp system was supposed to work, I didn't even know that shore charged the battery. My question stemmed from the fact that my trailer has some lights that only work on shore and some that only work on battery. What I'm going to do is make everything run off 12v battery and have the shore power just charge the battery when hooked up. Then I'll get a small DC to AC inverter so that I can have an outlet just in case. That will do everything I want to do.
Sounds like you are on it!
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Old 07-31-2013, 02:38 PM   #14
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Why not just change out the existing 120 VAC light fixtures out for 12VDC LEDs. It's not very efficient use of your battery when you have to use an inverter just to turn on a light.
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