What another solar question ????? - Fiberglass RV


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Old 05-02-2016, 08:30 AM   #1
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Name: todd
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What another solar question ?????

Hi All,

I am interested in putting solar panels on or by my TV, I would like to have the batteries there because the Casita is rather tight and does not have the space for two AGM's ( of course one could be in the cabin and one in the battery compartment but just for the sake of argument I want both in the truck). Also I would like to have the camper in the shade and the truck in the sun.

I know RVSue has done it, and I have asked her and unfortunately she can not answer how her system works. She has 24v volt panel that feeds two optima batteries and there is a third optima in her casita. There is a power cord running to the casita that attaches with an Anderson plug. I suspect she has an inverter in her TV.

Can someone please tell me how one would connect this system up. I am thinkin two 125 amp/hr AGM's or so and a 300 watt panel.

Thoughts/Suggestions

Thanks
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Old 05-02-2016, 08:52 AM   #2
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I have a 17 ft Casita Spirit Deluxe with a single 27F deep cycle battery and a 100 watt Renogy portable solar panel . We have camped for extended periods of time without utility hookups and have not had a battery / power issue. We do have LED lights and are not attempting to run any 120 VAC appliances. In my estimation, one would have to have a special need or use a lot of power to warrant 3 batteries and 300 watts of solar.
You could put 2 of the batteries in series and charge them at 24 VDC . 24 VDC would help eliminate voltage drop but your trailer still only accepts 12 VDC.
At some point and usage a generator makes more sense. Solar in not the answer in every case. A generator may be the cheaper / practical alternative . The weight of 2 batteries and the weight of a generator are probably a tossup. I am not a fan of generators but they should be considered.
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Old 05-02-2016, 09:22 AM   #3
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Thanks Steve,

Alot of times on the forum you get replies that don't address the question. Not that I don't respect your comments but I would like to know because I don't and somebody must.

If the batteries are on the truck what is the best way to get that power to the camper. Running 24 volts does cut down alot on wire losses.

Convert to ac and run a lead that way.

run dc to an inverter on the camper, are there otherways?

And how does one use that camper battery?

FYI I am gearing up to full time and I want to be prepared.

have a LD-17, a single 100 watt renogy, 30 amp charge control PMW, and a shunt connected to a battery meter so I know exactly how much is coming and going out. The parasitic loads alone are 0.12 amp per hr.

I would like to have enough reserve for cloudy days, I need a cpap and maybe the furnace and I already have a yamaha 2400 generator. I want to not worry about if I have enough juice.
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Old 05-02-2016, 09:38 AM   #4
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A couple of things to consider -

What are your actual electrical needs? If you haven't done an assessment of your actual usage, it might be worth doing this before putting together a system. As Steve notes, he does fine with one battery & a 100 Watt panel. Others may need more. His use of LED lighting is probably the best electrical usage reduction device available. While an oversized system is probably more practical than an undersized one, the cost differences between a 100 watt portable panel & 300 watts system mounted on the roof is considerable.

Some other sizing considerations - Do you winter camp? Permanently mounted, non tillable panels will produce well below their rating with low angle winter sun & shorter daylight hours. In my case, I have 195 watts of solar panels on the trailer roof & a pair of 6V, 232 amp hour batteries. That provides all my needs (including using an inverter to make toast & a pot of coffee) during the summer, but I found I needed to add a 160 watt portable panel during the winter, even in the southwest where there were mostly clear skies.

Do you want/need an inverter? If so, where will you locate it? If it is in the TV, you will need high voltage wiring & connectors to get the 120V output to the trailer, and a safe way to tie it into the trailer wiring.

On the other hand, if it is in the trailer, you will need very large wire (and connectors) between the TV & trailer to prevent voltage drop below the low voltage shut off on the inverter. To operate a 1000 watt inverter at full load you will likely need a pair of 4/0 cables (about 5/8" diameter) between the tow vehicle & the trailer.

The majority of 300 Watt, 24V panels are actually 36V panels that will require a more expensive MPPT controller to work with 12V batteries. Doing the same with a pair of 150 Watt, 12V panels will allow a PWM controller, and for small systems, not much of a change in efficiency. There is considerable controversy on the choice between MPPT & PWM controllers, but in general, most agree that for small (under 400 - 500 watt) systems, there is more usable power by using the additional cost of the MPPT controller to buy an additional panel & use a PWM controller.

On Edit - Your post while i was typing mine suggests you were considering a 24V system to feed a trailer mounted inverter. That would cut the current in half, and allow the use of a PWM controller with a 24V panel so that may be a practical compromise between running 12V or 120V between the TV & trailer. Again, while going to 24V would reduce the necessary wire size, it is still going to be fairly large cables & connectors, depending on the size of the inverter. If you are going to use the 24V TV battery bank to supplement the 12V trailer system, you will need a DC to DC voltage converter (which could be an inexpensive solar PWM controller).
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Old 05-02-2016, 10:30 AM   #5
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Quote:
Originally Posted by tmaken2157 View Post
...
Alot of times on the forum you get replies that don't address the question. Not that I don't respect your comments but I would like to know because I don't and somebody must....
I think you mean most of the time...

ME: "Honey, I'm going to to the store and get some beer."
WIFE: "Are you sure you want to do that? Do really need more beer? How much is it going to cost? Can't you wait till it is on sale? How much do you drink anyway? Etc.."
ME: "Nevermind, I'm going to the bar instead."

Since you have the same TriMetric meter that I have, I know that you have a good handle on your needs and wants. I do think that having a need for medical gear is one of the few good reasons to have a generator for a back-up in the worst case scenario, and would likely allow you to scale back a little to match your typical usage instead of theoretical maximum, but that is up to you.

I suppose you could set it up just like many of the dual battery setups documented all over the net, two 12 volt batteries in parallel or two 6 volt golf batteries in series for example, just move the batteries to the tug. The important thing is to use the proper cabling, esp to the trailer.

Knowing the total max load you will pull from the batteries and the distance to it, you can figure the wire gauge and fuse. Don't plan on going very far from the trailer however (your plan to have trailer in the shade and tug in the sun might not work most of the time). Some sort of high current connectors will be needed. Anderson Powerpoles are typical not water proof although they do have boots for their high current "SB Series" connectors.

Are you using the bed of a pick-up for the batteries?

If 120 VAC is only needed for the CPAP, then have you looked at 12 VDC models? I have no experience with them but I have seen other people use 12 VDC CPAP machines in camping trailers.
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Old 05-02-2016, 10:50 AM   #6
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Thanks Folks, We are getting close. For now disregard the particulars regarding appropriate size and whats really required. I don't know how much I need, but winter sun angles, my cpap, the furnace coming on, the tv going, fans, water pump, the parasitics...they all add up but this year I will be taking better notes. Believe me I have been doing my home work and thats why I'm confused when I saw RV Sue's blog, she did have professional to the install

Lets say two batteries, panel and 1000-1500 watt inverter in the truck bed.

I believe her system is running 120 volt back to the camper through an inverter and appropriate wire. Where/how would one tie that power into the camper.

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Old 05-02-2016, 11:33 AM   #7
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With the solar panels attached or near your tow vehicle ,and the batteries , solar controller , and inverter in your TV , you could run 120 VAC from the inverter and just plug your trailer as if you were plugged into a pedestal. The trailer doesn't know or care what the source of the 120 VAC is. The trailer's converter will allow your to charge your onboard battery and you could also run your CPAP or other small appliances on the trailer's 120 VAC circuits. Since the maximum current a 1500 watt inverter can supply is 12.5 amps at 120 VAC , a 12/3 cord would allow you to park your TV 50 ft away from the trailer. You could build a power center in your TV with a 120 VAC pigtail coming off the inverter and then just plug the 12/3 extension cord into the inverter's pigtail and plug the trailer into the other end of the cord. It's a lot easier to roll up and store a 12/3 cord than a coil of 4/0 wire.
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Old 05-02-2016, 11:58 AM   #8
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Sounds pretty reasonable and basically simple.

Thanks Steve
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Old 05-02-2016, 12:05 PM   #9
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One advantage of the inverter in the TV is the cooling fan noise while not loud is noticeable inside a camper.

On the down side going to 110 v inside the TV and plugging in your camper you will probably be hitting your converter which will then go through a second transformation (with I expect some power loss) to power the 12 volt circuits.

What about just making a Bargman 7 pin plug extension cord that only has power and ground wire, just plug in your TV battery and solar setup to the trailer plug. etrailer sells single pair 10 gauge wire with jacket for $1.21 per foot and that should work.

https://www.etrailer.com/Accessories...ka/10-2-1.html

Come to think of it this would charge any onboard battery as well as run the 12 volt systems. I guess you could even look at running the TV hitch power wire off your solar/battery in the TV while going down the road rather than wiring into the alternator. Might have to work out the ground wire since they are a different circuit than the lights.

Or just use that wire and a trolling motor 12 volt plug. One on the TV and one pigtailed to the trailer 12 volt system or with spade connectors that plug into the trailer plug at the hitch.

My own inclination would be to try to feed in 12 volt where 12 volt system of trailer expects 12 volt feed. Only if I required 110 volt AC broadly would I want to go through the shore power cord, I just think there would be too high of losses running through the transformer to power 12 volt and potential for some 110 volt item to draw down the batteries, say leaving a coffee pot on. Or a 110 heater plugged in. I'm on battery I want things to function like I'm on battery.
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Old 05-02-2016, 02:57 PM   #10
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Name: todd
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I like the inverter sound being in the truck. According to Steve If we need ac for anything I can just use an extension cord.


I also really like your suggestion Rogerdat that keeps things separate.

So

"Or just use that wire and a trolling motor 12 volt plug. One on the TV and one pigtailed to the trailer 12 volt system or with spade connectors that plug into the trailer plug at the hitch."

Sorry to sound dumb but would a connection like that also help to charge the trailer battery. I assume all batteries should be the same type and age ideally.


I see in my future a situation where I have two rv's, one for a home base that is "larger" and roomier, and the casita for the warmer weather adventures, so I would prefer to have the bulk of the solar systems in the truck.

Thanks for your input, much appreciate



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Old 05-02-2016, 04:41 PM   #11
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As mentioned you do need to get a handle on your power requriements and then size your inverter accordingly. What do you plan on using in your trailer that could possibly require a 1000-1500 watt inverter? The cost of properly sized wire between your truck and trailer will make you cry.


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Old 05-02-2016, 04:48 PM   #12
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Another thread on CPAP
CPAP machine & Boondocking/Dry Camping


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Old 05-02-2016, 05:00 PM   #13
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As mentioned you do need to get a handle on your power requriements and then size your inverter accordingly. What do you plan on using in your trailer that could possibly require a 1000-1500 watt inverter? The cost of properly sized wire between your truck and trailer will make you cry.


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The last time I purchase 4/0 THHN CU wire it was almost $5 / ft
That price was based on buying a 1000 ft spool and was at wholesale cost . As I said before if the OP placed the inverter in his TV and ran 120 AC from the inverter to the trailer ,he could get by with a #12 /3 ext cord , at a cost of $40 for a 50 ft cord. If the OP plans on running an electric coffee pot , frypan , toaster , hair dryer etc a 1500 watt inverter make sense. Plus leaving $400 to $500 worth of 4/0 cable laying on the ground is awfully tempting to thieves. There is a reason utilities use higher transmission voltages
IE - Less line loss , lower current , the ability to run smaller conductors and a huge cost savings.
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Old 05-02-2016, 05:24 PM   #14
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"I assume all batteries should be the same type and age ideally."

Yes or your new battery will be only as good as the old one


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