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Author Topic: A/B switch to switch between AC shore power and DC house battery?  (Read 1670 times)

sprinterlivingkc

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Campervan setup with two 6v golf cart deep cycle batteries and an inverter.  Id like to install some sort of switch to select either shore 30a power common in state parks and rv parks, or my house batteries.  Goal would be convenience; right now, if I want to use shore power, I have to manually move the plug in heads for all appliances from the inverter to the incoming shore power outlet, which is mounted in an out of the way area. 

Is there some simple 2-position switch that would accommodate this?   Not looking to spend a whole lot.  Thinking up to $15-20.  Would a simple light switch work?  DC battery connected to the off position and the shore power connected to the on position?  Or something like this? 

https://www.amazon.com/uxcell%C2%AE-Mounting-2-Position-3-Phase-Changeover/dp/B00NWGLYCM/ref=pd_sim_sbs_86_3?ie=UTF8&dpID=51onOjxATCL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&psc=1&refRID=77C72SZNBMDTVDT0JXKF

Are there issues with the different types of power on the same switch?  AC/DC?  Am I niave to think it is this simple to change between power sources? 

legrandnormand

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #1 on: August 16, 2016, 02:44:06 PM »
You are way out concerning electricity! Some appliances, like the roof air conditionner and the microwave only work on 115VAC, all the rest, works on 12 VOLTS, therefore, you cannot use the same switch to control 2 different voltages.
So this means that without electricity from the campsite or the state park, you won't have any air conditionning, or microwave and probably no TV unless you have a 12 VOLTS TV, which I doute.
« Last Edit: August 16, 2016, 02:48:45 PM by legrandnormand »
Normand
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Old Radios

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #2 on: August 16, 2016, 03:07:03 PM »
He has an inverter to run some AC appliances off the battery.  He's not talking about switching the AC and DC.  I doubt he's running the air and a microwave.
When he plugs into shore power he has to move the AC plug from the AC output of the inverter to the outlet for shore power.

My question would be why isn't shore power running a converter that charges the house battery?  It should and then no moving the AC plug is needed.
The shore power should be hooked up to a converter which in turn could supply the DC to run the inverter and charge the battery.
« Last Edit: August 16, 2016, 03:10:26 PM by Old Radios »
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legrandnormand

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #3 on: August 16, 2016, 03:31:09 PM »
He mentioned "campervan" setup... I doute that he even has an converter !  ;)  If he does have a converter, it should be wired properly to charge the batteries and to run his 115VAC appliances, if he has any !
If he's not plugged in, he'll only have the batteries to run the 12 VOLTS appliances, like a propane fridge and furnace and some lights.
Normand
Trois-Rivieres, QC, Canada
2010 Gulfstream Independance, model 8367
2009 Smart Cabriolet

Rene T

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #4 on: August 16, 2016, 03:49:10 PM »
Are you looking for something like this. When hooked up to shore power, it goes right through the switch. When you disconnect, it automatically switches over to your batteries.

https://www.amazon.com/Xantrex-Inline-Transfer-Relay-PROwatt/dp/B004S5Y158
Rene & Lucille & co-pilot Buddy
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From the Granite State of NH
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supermanotorious

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #5 on: August 16, 2016, 04:01:28 PM »
This is what I use

https://amzn.com/B000JJM7ZS
Home is Phoenix, AZ
2008 Skyline Freestyle M-240 Way-Lite
2003 Harley Davidson Dyna FXDX
2003 Chevrolet Avalanche 2500 8.1L 496ci 4x4
1994 Four Winns Freedom
various quads, off-road gokarts, mini bikes
Phoenix Winch wakeboard winches

sprinterlivingkc

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #6 on: August 16, 2016, 04:32:05 PM »
yeah, its a homemade campervan, so no converter present.  Is that how this is handled for all the people using manufactured RVs and such?   I'll be dry camping more often, so the batteries will be the primary source, and no ac or microwave with those.  Im basically running LED lights, fantastic fan, and coffee maker......although Id like to get a small 3.5 cu ft fridge going if possible (but Im guessing that would completely drain and kill my batteries in just one night). 

Looking at the Xantrex unit, it seems to be exactly what Im needing but cant believe the cost for something that simple (easier and cheaper to simply continue moving my plug heads)...appreciate the tips and comments all, I'll just keep noodling on this....thanks fellas!

Gary RV_Wizard

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #7 on: August 16, 2016, 04:58:00 PM »
Plug all the appliance cords into an outlet strip, either portable or a large hardwired one.   Then plug that strip into either the inverter outlet or a shore outlet, using an extension cord if needed. Here are a bunch of outlet strips, and you can get most sizes inexpensively at Walmart, Home Depot, etc.
http://www.tripplite.com/products/power-strips~20

You can make a simple power transfer switch using a DPDT (Double Pole, Double Throw) switch. Not a light switch. They are not expensive, under $10 for even a large size (30A or so).
http://www.learningaboutelectronics.com/Articles/Double-pole-double-throw-switch-DPDT
Gary
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Home: Ocala National Forest, FL

Len and Jo

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #8 on: August 16, 2016, 05:26:01 PM »
We use a 20amp DTDP switch to go between shore (E) and Xantrex inverter (I).   Center position is OFF.  We also have two 6v golf cart batteries and a small 3.2cf refrig.  ~$7 Home Depot, ACE Hardware, etc.
« Last Edit: August 16, 2016, 05:28:32 PM by Len and Jo »
Len & Jo
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We 'B' RVing   Berkley, Michigan
Van Development:   https://youtu.be/5Xqk_G6k95M
12 Years of Travels:  https://youtu.be/UMIf17CzdZo

supermanotorious

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #9 on: August 16, 2016, 05:32:31 PM »
I'm getting ready to install a DPDT again, in our new hauler. My way is harder to set up but has the best outcome- totally automatic, you don't have to think to remember to flip a switch.
Home is Phoenix, AZ
2008 Skyline Freestyle M-240 Way-Lite
2003 Harley Davidson Dyna FXDX
2003 Chevrolet Avalanche 2500 8.1L 496ci 4x4
1994 Four Winns Freedom
various quads, off-road gokarts, mini bikes
Phoenix Winch wakeboard winches

sprinterlivingkc

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #10 on: August 16, 2016, 05:34:23 PM »
We use a 20amp DTDP switch to go between shore (E) and Xantrex inverter (I).   Center position is OFF.  We also have two 6v golf cart batteries and a small 3.2cf refrig.  ~$7 Home Depot, ACE Hardware, etc.

ooooh!  thats the exact fridge and batt combo that Im setup with!  Can I ask how long you can get away with running the fridge before the batts get too low?  Ive also just ordered a new xantrex 1500 watt inverter....curious what you're experience is with running that fridge? 

sprinterlivingkc

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #11 on: August 16, 2016, 05:36:48 PM »
Plug all the appliance cords into an outlet strip, either portable or a large hardwired one.   Then plug that strip into either the inverter outlet or a shore outlet, using an extension cord if needed. Here are a bunch of outlet strips, and you can get most sizes inexpensively at Walmart, Home Depot, etc.
http://www.tripplite.com/products/power-strips~20

You can make a simple power transfer switch using a DPDT (Double Pole, Double Throw) switch. Not a light switch. They are not expensive, under $10 for even a large size (30A or so).
http://www.learningaboutelectronics.com/Articles/Double-pole-double-throw-switch-DPDT

You read my mind....I realized after posting the question that I could simply extend the shore power outlet under the bed with a power strip and mount it next to the inverter.....

I was looking at the DpDT switches and wondered if theyd actually work....thanks!  I may still do that!  And theyre nice and small....and cheap!  thanks again guys.

sprinterlivingkc

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #12 on: August 16, 2016, 05:37:48 PM »
I'm getting ready to install a DPDT again, in our new hauler. My way is harder to set up but has the best outcome- totally automatic, you don't have to think to remember to flip a switch.

Can I ask how you install that dpdt switch?  Im not sure I'll get it done before leaving, but sure would be nice to have it be automatic....Im a forgetful guy.

Len and Jo

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #13 on: August 16, 2016, 05:41:03 PM »
Refrig run time depends on your specific power draw.  We can run 2 days in hot weather (85F+) and 3-4 days in cooler weather (72F-).  BUT the Xantrex has a low battery warning alarm build in the triggers at 11.5 volts.  When our batteries get to about 70% SOC the Xantrex will beep for a half second when the refrig kicks on.  So not wanting to hear that we recharge at 75% SOC with the generator (assuming parking in shade and solar not keeping batteries charged).
Len & Jo
The Green Tardis
We 'B' RVing   Berkley, Michigan
Van Development:   https://youtu.be/5Xqk_G6k95M
12 Years of Travels:  https://youtu.be/UMIf17CzdZo

Rene T

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #14 on: August 16, 2016, 05:42:21 PM »
Can I ask how you install that dpdt switch?  Im not sure I'll get it done before leaving, but sure would be nice to have it be automatic....Im a forgetful guy.

It's not automatic if you have to physically switch it back and forth.
Rene & Lucille & co-pilot Buddy
AKA  Pep N Mem
2011 Chevy Duramax 2500 HD 4X4
2011 Montana High Country 343RL
From the Granite State of NH
& Florida Snowbird in Lakeland FL

supermanotorious

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #15 on: August 16, 2016, 05:46:11 PM »
The DPDT relay I linked above, your inverter output goes to the normally closed contacts on the input side of the DPDT relay, your incoming shore power goes to the normally open contacts on the input side of the DPDT relay, you also connect incoming shore power to the magnet (coil), then your coach wiring goes to the output contacts of the DPDT relay

I'll make a diagram and post soon

Page 4 of this thread shows my work http://www.rvforum.net/SMF_forum/index.php/topic,91264.90.html

I'll make a cleaner write up with the next project, your install will be more simple as you do not need to worry about bypassing a converter's charging wire
« Last Edit: August 16, 2016, 05:55:33 PM by supermanotorious »
Home is Phoenix, AZ
2008 Skyline Freestyle M-240 Way-Lite
2003 Harley Davidson Dyna FXDX
2003 Chevrolet Avalanche 2500 8.1L 496ci 4x4
1994 Four Winns Freedom
various quads, off-road gokarts, mini bikes
Phoenix Winch wakeboard winches

supermanotorious

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    • Phoenix Winch LLC
Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #16 on: August 16, 2016, 07:15:19 PM »
here it is (I hope)

the bottom middle terminals are the coil, which when shore power is present, automatically throws the relay to shore, you only need to piggy back a thin gauge wire from shore power to the coil

hopefully you can see that since the inverter is on the normally closed or connected side, you  waste no energy keeping the inverter selected

Home is Phoenix, AZ
2008 Skyline Freestyle M-240 Way-Lite
2003 Harley Davidson Dyna FXDX
2003 Chevrolet Avalanche 2500 8.1L 496ci 4x4
1994 Four Winns Freedom
various quads, off-road gokarts, mini bikes
Phoenix Winch wakeboard winches

John From Detroit

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #17 on: August 17, 2016, 05:09:31 AM »
I have an inverter that powers SELECTED outlets on this RV when I'm not plugged into shore power

Microwave
Televisions and associated electronics
GFCI chain (kitchen, Bath, patio, Dining Table)
And the outlet at the co-pilot's feet. (Television circuit)

Optionally (30 amp DPDT switch) it can power the fridge and bedroom outlets (same circuit)

The switch came from an electrical supply house,, Yes they are expensive.

The Inverter is an "inline" type True Sine wave

What this means is simply this.. When the fuse failed and half the park (My half of course) lost shore power a couple weeks ago.. The Televisions and computers did not BLINK,, they kept on working,,, ,The Microwave clock did not go out or blink 12:00 12:00 when power came back.. In fact had the Air Conditioenrs not stopped I'd not have noticed.

The switch is built into the Inverter.

In-line inverters not only make 120 vac out of 12vac when no shore power is present.. but if you have shore (or generator) power they do the INVERSE and convert 120vac to 12vdc to recharge. ... Kind of like a UPS. (Kind of exactly a UPS)
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GA_Boy

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #18 on: August 17, 2016, 10:53:45 AM »
When I had the "B" I ran 12/2 wire parallel to my existing wiring and connected to different color recepts.  The other end had a male 20 amp plug to use with the inverter. If I need the inverter I would plug in my yellow recepts, turn on the inverter and use as needed.  It would run everything except the A/C. It ran the small Microwave OK. 
SEE PICTURES
Marvin
 (http://i938.photobucket.com/albums/ad222/GA_Boy/Van%20RV/1200wattinverter_zps9d706b9d.jpg)

(http://i938.photobucket.com/albums/ad222/GA_Boy/Van%20RV/Yellowis110Vfrominverter_zpsf28e187e.jpg)

(http://i938.photobucket.com/albums/ad222/GA_Boy/Van%20RV/Yellowis110Voltfrominverter_zpsa2b39ca0.jpg)

Old Radios

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #19 on: August 17, 2016, 02:21:49 PM »
If you are mainly running on batteries you might want to ditch the electric coffee pot and get an old fashioned percolator and use it on the stove. We've been using one for a few years and don't miss an electric at all.   My wife thinks the coffee tastes better.
2006 Fleetwood Tioga 26Q
2010 Harley Softail Custom Toad
2015 Harley Softail Deluxe Toad
2015 Ford Focus Toad
Upstate (the other) New York

Len and Jo

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #20 on: August 17, 2016, 11:06:33 PM »
I personally do not see a problem with throwing a toggle switch.  We are using the inverter 120vac while driving. If we stop in an RV park that has shore power we have to get out a power cord to plug in the van so remembering to turn off the inverter and switch the toggle over from inverter to shore is a minor point.  We also have a small night light plugged into a duplex outlet near the front of the van so we can visually see that our outlets are powered. 
Len & Jo
The Green Tardis
We 'B' RVing   Berkley, Michigan
Van Development:   https://youtu.be/5Xqk_G6k95M
12 Years of Travels:  https://youtu.be/UMIf17CzdZo

robertusa123

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Re: A/B switch to switch between AC shore power and DC house battery?
« Reply #21 on: August 22, 2016, 04:06:44 PM »
The easiest way to do that is with a standard 3way light switch.     The common screw goes to rv outlets and stuff. One of the travlesr go to shoure power and the other to invider.   You would share the neutral and ground
1996  26ft. 3 kids 2 dog and the wife too

 

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