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Old 07-03-2012, 03:09 PM   #1
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Hello and need help on Solar Controller/RV Converter ether/or switch

First hello people, new to RV solar and excited. I'm attempting to be a weekend boondocker. I have a 2013 Rockwood Ultralite 2501SS (my second TT). Read Handy Bob's blog and so much other stuff I can't remember it all but got very interested. I have a Morningstar SS MPPT 15L with RTS (remote temp sensor) and MSC (PC Meterbus Adapter) on the way. I believe I have my portable solar system figured out with one exception. Just talked to Morningstar and absolutely positively not allowed to run charge voltage from the WFCO 8955 backwards through the SS MPPT. My brain is mush right now but I could swear I have not read about any wiring configurations where I can have my solar power the RV and charge the battery, then have the WFCO power the RV and charge the battery. I'm thinking some kind of ether/or switch with a by pass diode (can you say end around carry?). I could label it simple like SOLAR OFF SHORE and rest assured I wouldn't confuse it after a couple pints OY!

Thanks, Jeff
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Old 07-04-2012, 05:58 AM   #2
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Welcome to irv2.
Here is some more reading for Solar that might help you out.
Would think the control units would control the charge of your batteries while you are using the solar power system.

Needs for boondocking.
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Old 07-05-2012, 08:28 AM   #3
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Thanks for the new resource 007 but pretty much a rehash of all I have already learned.

I guess another way of coming at this is to ask why are there separate negative terminals for battery and load? Do they need to be isolated for monitoring? If so then I have to disconnect the battery negative from the RV frame and connect it to the SSMPPT "battery" negative terminal then connect the SSMPPT "load" negative terminal to the RV frame while in solar mode. I will then have to undo this to get back to shore mode no?

Thanks, Jeff
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Old 07-05-2012, 10:12 AM   #4
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All your negative connections can remain where they are, frame, battery, ground rod, wherever you have them, they are common.

The 'load' and 'battery' positions on the controller are internally connected. The reason for having two different positions and connections is to protect the battery in the event of low voltage.

An example would be, late one night you had to look in a compartment and you forgot and left the light on, the 12 volt light running off the battery bank. You are draining the battery so the controller will disconnect the load at a predetermined battery level, thereby killing the offending light and saving your battery from going DOA.

It's the same with your inverter, it'll drop out at 10 volts to save your batteries too, providing it's a quality inverter.

That's it in a nut shell.
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Old 07-05-2012, 10:57 AM   #5
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Thanks Sundancer87, just got off the phone with Morningstar Tech and your right, they are in fact internally connected. The negative "load" terminal is just so your certain the load is disconnected in your mind. So in my crude little drawing my "transfer" (either/or) switch will move the RV from the load terminals to the battery both positive and negative. I'm thinking I only need to move the positive? What say you?

By the way, I'm doing this portable so the solar panel will only be connected when the switch is in the "up" position as the drawing sits.

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Old 07-05-2012, 07:16 PM   #6
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So after re-reading and digesting I now believe this is correct.


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Old 07-06-2012, 09:53 AM   #7
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I don't quite understand for the switching of the system.

If you want to use the switch as a disconnect when removing/installing the panels or servicing the system then that's a good idea. A simple fused disconnect will work for this purpose. Regarding your question about which leg to disconnect I lean towards positive. My feeling is the positive is basically available at certain locations whereas a ground could be found many places so the safety factor is somewhat lessened. There may be a rule of thumb about this but that's the way I've lived solar for 20 years.

Now, if you are switching because of a converter conflict or solar conflict or generator charging, it's not necessary at all.

Your solar system will be paralleled to the battery bank, the converter will the same way. The generator could be connected to the converter to charge the batteries, this I don't know but would be ok.

To give you and idea of what I live with, 6 6 volt true deep cycle batteries, 12 panels of various age and output but good for 30 plus amps all day, 2400 inverter (no converter), a 20 year old analog charge controller ( do have a 30 amp Morningstar as backup), 400 watt wind generator and a 6010 Honda MH generator that powers my A/C in the middle of summer.
Every connection of these components are paralleled to the battery bank. When I run the Honda generator the inverter charges my batteries while supplying voltage to the A/C. When the wind blows the generator charges the battery bank at the same time the sun is charging the batteries.
All three charging components can be charging the battery bank at one time. No switches except internal to each component and one 400 amp primary total disconnect. The wind machine and solar panels each have their respective disconnects.
Overall, there isn't any need to isolate each of these things form each other.
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Old 07-06-2012, 10:09 AM   #8
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Quote:
Originally Posted by sundancer87 View Post
I don't quite understand for the switching of the system.
Ah ha, Ok, it's for measuring load. When I chop the battery positive lead in half and place the controller in-line with battery positive connected straight to the controller battery terminals and RV positive connected straight to the load terminals I can see what's going on. The only way the RV gets 12v power is through the controller so all RV load is measured. Connected like this the only way for the RV converter to charge the battery is to run backwards through the controller.

Thanks, Jeff
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Old 07-06-2012, 10:41 AM   #9
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There are amp hour meters that will tell you how many amp hours have been consumed from your batteries. These meters count both ways, what is used and what has been replaced.

Metering

There are others also but something to look at if you are wanting to watch your consumption without installing switches and extra wiring.

Cruising Equipment E-Meter Amp-Hour Meter
This is the one I've been watching for 20 years.
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Old 07-07-2012, 09:09 PM   #10
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Ah ha, Ok, it's for measuring load. When I chop the battery positive lead in half and place the controller in-line with battery positive connected straight to the controller battery terminals and RV positive connected straight to the load terminals I can see what's going on. The only way the RV gets 12v power is through the controller so all RV load is measured. Connected like this the only way for the RV converter to charge the battery is to run backwards through the controller.

Thanks, Jeff
NO. The RV gets 12V power from your 12V fuse panel.

I have the Sun Saver Duo. Didn't need the MPPT but did read up on it when I was assembling all my solar equipment.

All your 12V DC loads come off your DC fuse panel already located in your RV or any other wires/fuses/relays you add yourself.

The "load" position on the SS controller is referred to as "light/load" from Morningstar. It is strictly there to allow you power a light(s) or other load that will come on at night and go off at sunrise(night lights). For this capability to work you would obviously have to mount the charge controller where it sees sunlight unlike mine which is in a closed, dark compartment.

I also don't even see how it would be possible to send 12VDC backwards through the charge controller. Even if you tried; the only place power could go is back up to the solar panels. Solar panels dont take 12 VDC and make sunlight, they take sunlight and make DC voltage. Besides the panels have blocking diodes to prevent voltage from flowing the wrong way. So you wont damage anything by charging your batteries from shore power while the charge controller is still hooked up. This is the normal configuration for any solar charging system and I dont know of anybody else who disconnects their controller whenver they hook up to shore power.

All you need to do is wire your panels into the charge controller and run the output from the controller to your battery bank. The solar panels aren't running your loads they are just charging your batteries. If you use the "load" connections on the controller I imagine it would only be a couple small loads. Again the controller and panels aren't powering the loads this way, the controller is just acting as a sunlight activated relay to allow power from your batteries to flow back through the controller to the selected load(s)(even though its not really flowing "back").

There is no need to disconnect any part of the solar system when hooked up to shore power or running a generator to charge the batteries, nothing is gonna flow backwards thru the controller or hurt the controller, you'll just be charging the batteries from more than one location. I've had shore power hooked up charging the batteries at the same time my generator in the sky was shining putting 11 amps into the batteries.

Try not to over analyze too much. Good luck.
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Old 07-08-2012, 07:05 AM   #11
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First let me say thanks for taking the time to respond, it's appreciated.

Quote:
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NO. The RV gets 12V power from your 12V fuse panel.
Correct, AND the 12v fuse panel gets this power from either the converter or the batteries.


Quote:
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The "load" position on the SS controller is referred to as "light/load" from Morningstar. It is strictly there to allow you power a light(s) or other load that will come on at night and go off at sunrise(night lights).
Sorry but you don't have it completely correct here. Yes the SunSaver MPPT has the ability to control lighting but I'm not using this at all. After talking with MorningStar the lighting control function didn't even exist until version 9 of the firmware and even then it's disabled by default. To accurately measure power consumption using the SS-MPPT controller's built in capabilities ALL load MUST be connected to the load terminals. I just have to ensure I never attempt to draw more than 15 amps. I did a quick little survey using an inductive DC amp meter and separate volt meter. Here is what I found at 12.5 volts...

Phantom _ 0.39 amps
Fridge __ 0.75 amps
Fan 1 ___ 1.21 amps
Fan 2 ___ 1.78 amps
Fan 3 ___ 2.54 amps
1 light _ 2.80 amps
Furnace _ 3.76 amps
Stereo __ 0.63 amps

Curious, I set the font of the above table to courier new and spaced everything so it would line up nice but doing a preview it was blasted away, oh well just have to use underscores.

As you can see this is possible. My biggest concern is the possible 7.0 amp draw of the water pump but this is only at the lowest flow just before shutdown. I'll never be using the fantastic fan at the same time as the furnace and am replacing all lights with LED.


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I also don't even see how it would be possible to send 12VDC backwards through the charge controller.
This should be answered now.

Quote:
Originally Posted by RLKBOB View Post
Try not to over analyze too much. Good luck.
Good one.
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Old 07-08-2012, 08:32 AM   #12
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OK, now that I see what you're talking about I still don't think you will need a transfer switch. Even if you run all the loads through the controller so they can be metered the converter(battery charger) is not a load, it's a power source. Your converter should be wired directly to the batteries for charging and there should be a completely independent wire feeding the DC fuse panel from the battery through a ckt bkr, at least this is how mine is set up. To avoid having to use the switch you're talking about just run the charging line from your solar panel(via controller obviously) to the battery, the charging line from the converter directly to the battery and relocate the wire that feeds the DC fuse panel from the battery to the load terminal on your controller.
The converter is never actually directly supplying the DC loads this way, it is just keeping the battery charged and the DC loads are, in turn, being drawn from the battery. This way you could never charge backwards thru the controller.
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Old 07-09-2012, 10:05 AM   #13
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To avoid having to use the switch you're talking about just run the charging line from your solar panel(via controller obviously) to the battery, the charging line from the converter directly to the battery and relocate the wire that feeds the DC fuse panel from the battery to the load terminal on your controller.
The converter is never actually directly supplying the DC loads this way, it is just keeping the battery charged and the DC loads are, in turn, being drawn from the battery. This way you could never charge backwards thru the controller.
I like this idea. If my trailer wasn't brand new with a 5 year bumper to bumper extended warranty I might go ahead and tear the fully enclosed underbelly apart and run this secondary wire from the converter/charger to the battery. While in there I might add more insulation etc.. As it is I have a single #8 red wire disappearing into the underbelly of my trailer with the other end showing up in my WFCO power distribution center. I don't really want to go mucking around in there.

With everyone's help I believe I have it figured out with this Blue Sea transfer switch. When we arrive at camp and finish setting up the final thing will be to switch the switch from it's "shore" position to the center or off position, connect the solar panel to it's water proof quick disconnect plug, switch the switch to the "solar" position and open a cold one.

Leaving is opposite, switch the switch to center, disconnect panel, switch to shore, connect truck.

Thanks all for the good discussion and good ideas.

- Jeff
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