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Old 05-19-2020, 08:04 AM   #1
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Basic RV Electrical Flow

All,

While looking through some threads and then some pictures of wiring I had taken, I thought I'd make a basic power flow diagram. One item I'm not sure about is how do the battery and AC/DC converter power mix? Where does it switch between battery power and power supplied via DC converter (when using gen or shore power)? Attached is a diagram I was making, does it look accurate?

Thanks-
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File Type: pdf RV Wiring.pdf (160.7 KB, 189 views)
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Old 05-19-2020, 11:58 AM   #2
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I'm not an expert, but I think the answer is it doesn't. In the two travel trailers I have owned, the converter has 12V and 120V circuits and a battery charger built into the unit. They functioned this way:

- Battery powers 12V
- Shore power powers 120V. On my older White Hawk, there was no 120V when there was no shore power. On my newer Eagle, there is a separate inverter that supplies some 120V circuits even on battery.
- When on shore power, charging circuit in the converter charges your batteries, thus making it seem like 12V is running directly off the shore power.

So, I don't think there is anything in the converter or elsewhere that is directly transforming the 120V shore power to 12V circuits, it just charges the battery. If you have a separate inverter, it is also hooked directly to the battery. There might be higher end units that include some type of smart inverter right in the "converter" package, but not on units I have owned.

A transfer switch only comes into play if you have multiple high voltage inputs, like shore power and a generator and you want to seamlessly switch between them.
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Old 05-19-2020, 01:20 PM   #3
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A couple things to correct:there is no relationship between the inverter and the transfer switch. The inverter has battery input and 120v input. The inverter does the switching of inputs to power the inverter supported outlets.
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Old 05-19-2020, 01:35 PM   #4
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Quote:
Originally Posted by morleyz View Post
I'm not an expert, but I think the answer is it doesn't. In the two travel trailers I have owned, the converter has 12V and 120V circuits and a battery charger built into the unit. They functioned this way:

- Battery powers 12V
- Shore power powers 120V. On my older White Hawk, there was no 120V when there was no shore power. On my newer Eagle, there is a separate inverter that supplies some 120V circuits even on battery.
- When on shore power, charging circuit in the converter charges your batteries, thus making it seem like 12V is running directly off the shore power.

So, I don't think there is anything in the converter or elsewhere that is directly transforming the 120V shore power to 12V circuits, it just charges the battery. If you have a separate inverter, it is also hooked directly to the battery. There might be higher end units that include some type of smart inverter right in the "converter" package, but not on units I have owned.

A transfer switch only comes into play if you have multiple high voltage inputs, like shore power and a generator and you want to seamlessly switch between them.
When on shore power the converter is always supplying 12 volts to the 12 volts buss bar to run all your 12 volt stuff AND charge the battery. Lighting and 12 volt control circuits are powered by the converter. The converter is powered by 120 volts on a 15 amp breaker. When not on shore power the battery does it all.
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Old 05-19-2020, 02:01 PM   #5
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Thanks for the input.

On the DC powered equipment; All DC powered hardware is only connected to battery and the AC/DC converter is charging the battery when using shore or gen. There is no AC->DC conversion when using shore or gen power.

On the transfer switch; I have a 15A AC transfer switch. (different unit from gen/shore transfer switch) This has 2 inputs, utility (assuming shore or gen) and inverter with a single output/load. I believe this guy powers the 1-2 AC outlets that work when not using shore or gen power. If gen or shore is used, it 'transfers' the source from battery to shore/gen power bypassing the inverter for those outlets. Do you guys think it may be for something else? Attaching a better picture.

The other AC outlets (bedroom, kitchen, microwave or bathroom GFI) only work when connected to shore or gen.
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File Type: pdf RV Wiring.pdf (163.8 KB, 17 views)
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Old 05-19-2020, 02:29 PM   #6
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Quote:
Originally Posted by mini4mw View Post
Thanks for the input.

On the DC powered equipment; All DC powered hardware is only connected to battery and the AC/DC converter is charging the battery when using shore or gen. There is no AC->DC conversion when using shore or gen power.

On the transfer switch; I have a 15A AC transfer switch. (different unit from gen/shore transfer switch) This has 2 inputs, utility (assuming shore or gen) and inverter with a single output/load. I believe this guy powers the 1-2 AC outlets that work when not using shore or gen power. If gen or shore is used, it 'transfers' the source from battery to shore/gen power bypassing the inverter for those outlets. Do you guys think it may be for something else? Attaching a better picture.

The other AC outlets (bedroom, kitchen, microwave or bathroom GFI) only work when connected to shore or gen.
There is AC to DC conversion when on shore power and Gen. That is what the converter does. My neighbor in camp has the same trailer as me with NO battery installed. The converter supply's to 12 volts to run the lights and the 12 volt control circuits for the equipment. He has no battery installed so it is not charging one. Your inverter is supplying you with 120 volts via the battery so you can watch TV while boon docking and anything else you wanna plug in to those two outlets.
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Old 05-19-2020, 02:49 PM   #7
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Right, sorry, I wrote that from a point of view in my head...

shore/gen AC power is converted to DC, DC only charges the battery. All DC equipment is only supplied power by the battery. DC equipment (lights, air conditioner, heater oven, etc) does not get power directly from a converter when plugged into AC power.
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Old 05-19-2020, 03:22 PM   #8
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Quote:
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Right, sorry, I wrote that from a point of view in my head...

shore/gen AC power is converted to DC, DC only charges the battery. All DC equipment is only supplied power by the battery. DC equipment (lights, air conditioner, heater oven, etc) does not get power directly from a converter when plugged into AC power.
Yes they do.12 volt control circuits and lights. See post #6. Neighbor is there 24/7 for 4 months. just like me. 2002 and 2008 wildcat 5er's.
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Old 05-19-2020, 03:28 PM   #9
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and to add to the mix some items still have to have batteries connected to operate on 12 volts.
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Old 05-19-2020, 04:03 PM   #10
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So how does the DC hardware connect? How are the power lines separated between battery power and converter? Are perhaps anchored to the same bus (at fuse panel perhaps), which would be series and just increase amps but keep voltage at 12?
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Old 05-19-2020, 04:29 PM   #11
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So how does the DC hardware connect? How are the power lines separated between battery power and converter? Are perhaps anchored to the same bus (at fuse panel perhaps), which would be series and just increase amps but keep voltage at 12?
I do not have a clue what you just said. A converter is a battery charger. It is powered by 120 volts. The output is 12 volts connected to the 12 volt fuse panel buss and to the battery. The actual output is 13 something but I don't remember. There are 2 reverse polarity fuses on the converter for converter protection from a miss wired battery. There is an inline resetable fuse within 6' of the battery. I don't understand your last sentence at all.
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Old 05-19-2020, 06:51 PM   #12
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"The output is 12 volts connected to the 12 volt fuse panel buss and to the battery"

So the AC/DC converter and the battery are connected to the 12V DC fuse buss. This is how AC provides DC power and battery also provides power.

What I meant by in series was that converter attaches to buss and battery attaches to buss. So you maintain 12V but you have converter amps + battery amps resulting in increased total amps at the 12V fuse panel (when attached to shore/running gen).
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Old 05-19-2020, 07:44 PM   #13
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Quote:
Originally Posted by mini4mw View Post
"The output is 12 volts connected to the 12 volt fuse panel buss and to the battery"

So the AC/DC converter and the battery are connected to the 12V DC fuse buss. This is how AC provides DC power and battery also provides power.

What I meant by in series was that converter attaches to buss and battery attaches to buss. So you maintain 12V but you have converter amps + battery amps resulting in increased total amps at the 12V fuse panel (when attached to shore/running gen).
I think my head is about to explode. Seems we are trying to make it more difficult than it needs to be.

First off, no battery=no inverter. It would be stupid to try to use an inverter by feeding it with 12 volts from a converter. I would assume that the transfer switch that works with the inverter will default to the 120 volt shore/generator input, if present, rather than switching to the inverter if it was powered up.

12 volt items are all powered by battery and/or converter. The converter will easily run all 12 volt items up to its limit. If your slide pulls big amps when extending, I would feel better having it fed by battery which could supply more current (typically) but since others operate without batteries, the converters must be up to the task.

Thinking about how I would wire a rig, I would bring the battery cables to a junction block and then to the fuse panel. I would also connect the converter to the junction block so it would be fed to the 12 volt battery buss prior to the fuse panel.

You asked about the amps available with both battery and converter. Just how many amps do you need? The amps available from the battery is only limited by cable size and length. If sized correctly you would get all the amps you would ever need from the battery. Forgetting about the inverter, the big 12 volt power draws that come to mind are slide motors and maybe an awning motor, which would be far less, and maybe the furnace which also would not be a major draw. I am just trying to think of things I run without shore power. Once again I skip the inverter since it is only used for TV in my case and it just loves to eat batteries.
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Old 05-19-2020, 07:48 PM   #14
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Quote:
Originally Posted by mini4mw View Post
"The output is 12 volts connected to the 12 volt fuse panel buss and to the battery"

So the AC/DC converter and the battery are connected to the 12V DC fuse buss. This is how AC provides DC power and battery also provides power.

What I meant by in series was that converter attaches to buss and battery attaches to buss. So you maintain 12V but you have converter amps + battery amps resulting in increased total amps at the 12V fuse panel (when attached to shore/running gen).
There is no total amps. Think of this as the Converter being the shore power and the battery being the generator. The battery and the generator do not add together. the converter supplies the 12 volt systems AND charges the battery. The battery only supplies the 12 volt systems.
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Old 05-19-2020, 07:51 PM   #15
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Jim, trying to discuss electrical systems on internet forums is a waste of time. Too many people who know enough to be dangerous or just plain guess proliferate the posts.
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Old 05-19-2020, 08:00 PM   #16
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I believe we're partially crossing paths on what we are talking about. It is difficult in writing. I'll get the electrical layout and dig more into it.

Thanks for the help.
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Old 05-20-2020, 07:10 AM   #17
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When on shore power the converter is always supplying 12 volts to the 12 volts buss bar to run all your 12 volt stuff AND charge the battery. Lighting and 12 volt control circuits are powered by the converter. The converter is powered by 120 volts on a 15 amp breaker. When not on shore power the battery does it all.
Neat. I didn't know this. On my White Hawk, I added a cheap disconnect on the + battery terminal and even with shore power hooked up, if I disconnected the battery there was no 12V power. Didn't think twice about it because I always had a battery.
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Old 05-20-2020, 11:23 AM   #18
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Neat. I didn't know this. On my White Hawk, I added a cheap disconnect on the + battery terminal and even with shore power hooked up, if I disconnected the battery there was no 12V power. Didn't think twice about it because I always had a battery.
Exactly, our trailer is currently plugged into shore power with the battery removed and all DC equipment is running as usual off the converters DC buss and fuse panel.
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Old 05-20-2020, 01:26 PM   #19
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Just following up for a little more closure. The wiring is not nearly as simple as I was expecting, but still easy to follow when reviewing the electrical diagrams. Some items are wired only to incoming 120V while the remaining 12V are dual homed to AC->DC converter and battery. Attaching a pic from the last question I was trying to understand.

If you email customer service with VIN/model they will send the wiring schematic which hopefully no one ever needs to use, but it certainly helpful when you do. Better to be prepared.
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Old 05-27-2020, 07:14 PM   #20
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Converter output voltage is 13.2 volts minimum. A good converter has three output levels: 13.2, 13.6 and 14.4 volts. Battery output voltage is 12.7 volts maximum. Electricity flows from higher voltage to lower voltage. In other words, the converter will supply ALL power needed for lights, etc. and will maintain battery charge.

A lot of confusion results from reading Trailer Life magazine. The info put out by the so called experts is crap. Converters do not "kick in". Batteries cannot be charged and supply power at the same time. Batteries do not power loads when on shore power, etc. My qualification is a degree from Purdue University in Electrical Engineering a long time ago. Yes, I know. Our football team leaves something to be desired. Hi Norty!
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