Another SOLAR question!!!

[joem789]

We have been living in a TT full time for well over a year. Now its high time we start weaning ourselves off of grid power. We will be moving our camper onto land without shore power. So we plan to get a generator. Primarily for running tools and such. But also as a crutch by plugging into the camper. But overall, we want to implement solar as much as possible. But GRADUALLY due to cost.

My biggest question here is this. (And I apologize if this has been discussed before, I couldnt find it)

Would it make sense to put together a smallish solar system and plug the generator and solar inverter into an auto transfer switch? Then plug that into the RV main outlet? Eliminating any modifications inside? I have a basic understanding of electricity and wiring. And realize that I would need to consider any DRAW there might be inside, sucking the life out of the batteries.

The idea here is to keep the solar batteries separate from the camper converter system. At present, we have a single deep cell on the camper, like traditionally seen. And I wonder if I might have to unhook that battery to keep from charging it using the solar batteries.

I hope someone can give me a good answer on this. THANKS!!

PS. Another reason I am thinking about keeping my solar system separate from the camper inside wiring is because we will eventually build a cabin that I will "move" the solar system to.

[Doug33]

The other factor may be location, which you do not list in your profile. This is especially true in the winter when the sun is at its lowest. The further north you are, the less sunlight you will get in the winter. So there will be significant fluctuations in availability throughout the seasons.

[joem789]

Ok. I ended up with (2) SolarWorld panels, 250 watts each. They are 30v panels. I ended up getting the MPPT Tracer 2210RN Solar Charge Controller since it was only $100 and seems to get rave reviews. I also got some 10AWG copper wire (50') since I am putting the panels on top of the RV right above where the battery bank sets. Finding batteries in my area is limited. So I went to Sams Club and picked up (2) Duracell GC2 Golf Cart batteries.

I am amazed at how the panels will put out the 30V even in a shade. They seem very efficient. But I am no expert.

Do I need to worry about the wire that runs from the camper to the battery? Normally this camper came out with a single low hour 12v deep cycle. I am taking it off and putting the two 6 volt batteries together. If the wire is okay, then do I have to worry when I go to add two more batteries in parallel? I just didnt know if this would put a heavier load on the camper wire.

[JiminDenver]

You can run things off of your solar system, you just have to have a big system and small loads. With a 230w system I can turn on every light, fan and even the furnace and have the solar provide the power. That power stops as soon as a cloud goes by or the sun goes down, so having a battery is kind of important.

I would suggest getting a general feel for what you need and how you will set it up before picking out specific components. Each interacts somehow with the others and a poor choice now can be limiting as you go along.

[joem789]

That's good to know. And thanks alot for clearing things up on the inverter. You mentioned that a PWM controller is only about $35+. Any particular one you would recommend? I had actually been looking at this Morningstar model, which apparently is overkill and expensive? http://www.amazon.com/MorningStar-ProStar-Battery-Controller-30/dp/B0070OS4JS

[pianotuna]

Solar charging plays well with other forms of battery replenishment.

joem789 wrote:
Thanks! That's helpful.

The other thing here is this. And I think a real important one. Having my solar system connected to the battery(or batteries) for charging. All the while they are still connected to the TT as usual. What happens if I decide to connect the camper to my generator while the solar is charging the batteries? It seems to me that the camper electrical system will try to charge the batteries at the same time as the solar? Will this be a problem? Will I need to disconnect the camper charger from the batteries at the fuse panel?

[Golden_HVAC]

SunElec.com had a 140 watt 12 volt solar panel for $229 a few weeks ago.

I would recommend spending the money on a PWM controller, not a more expensive MPPT controller. They are only about $35 for a 20 amp controller, good for 2 of the 140 watt panels.
Your RV will consume about 35 AH daily just to run the refrigerator, CO meter and propane leak detectors. This is about what one 120 watt panel will make in one day.

I lived full time in a RV with 400 watts of solar panels, and 4 golf cart batteries. Normally I did not need to run the generator, but might if I used more than 120 amp hours overnight. I liked to watch a lot of satellite TV each night.

I would also recommend a small inverter, like 200 - 500 watt size. It can plug into cigarette lighter, and run small things like a laptop, DVD player, TV set, all at once. I would not recommend a larger inverter, as they discharge the battery to quickly, and are not nearly as energy efficient.

I have a built in 1500 watt inverter, but normally use my portable 300 W inverter instead. It will use about 2 AH less than the larger one.

Good luck,

Fred.

[Muddydogs]

Nope doesn't matter if the solar is connected while camper is plugged in. What you need to know is the solar controller regulates the incoming solar to only charge at so much, most controllers are setable. The trailer converter if a 3 stage converter will change the voltage going to the batteries and if not a 3 stage then the converter is probably charging around 13.6 volts.

So when your trailer is plugged in and your batteries are charged your converter is only running a maintaining charge of say 13.6, well if your solar controller is set at 13.6 then the controller will basically shut off the flow from the solar panel. If your solar controller is set for 14.6 volts charging then your converter would be putting in 13.6 volts and the solar will make up the other 10 volts.

If you don't want your solar charging when plugged in then adjust your solar controller to the lowest charge setting. Most don't worry about adjusting anything when camping and leave their solar set around 14.6 and if they happen to run the generator it takes care of itself. The only time I touch my controller is when the trailer is in storage and the batteries are charged, I will then set my controller to a maintainer charge of 13.6 so I don't boil out the water with the trailer setting for a month or so.

[joem789]

Thanks! That's helpful.

The other thing here is this. And I think a real important one. Having my solar system connected to the battery(or batteries) for charging. All the while they are still connected to the TT as usual. What happens if I decide to connect the camper to my generator while the solar is charging the batteries? It seems to me that the camper electrical system will try to charge the batteries at the same time as the solar? Will this be a problem? Will I need to disconnect the camper charger from the batteries at the fuse panel?

[pianotuna]

Your biggest energy draw may be the laptop--depending on how many hours it is used.

A hair drier is going to require a 1000 inverter. That will demand 100 amps from the battery bank.


Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT.

Here is a link to the rather special spreadsheet that N8GS has created to help size solar battery charging systems!

Solar spreadsheet by N8GS

[joem789]

ok. thanks.

[ewarnerusa]

The 12 volt plug would work okay for a very small inverter, like 300 watts max, to run the TV. A hair dryer? No chance. It is the heating element in that that is the big draw. Over 1000 watts.

[joem789]

That's good news. It sounds simpler than I made it out to be. And I still need to solve the inverter issue. Whether or not I need to wire one to the batteries. Or if I can just use a small one plugged into the cigarette lighter in the bedroom. I honestly do not know how strong the wiring is for it. Whether it can handle a hair dryer or something with a "motor". Will it just blow the fuse or burn the camper down? lol

[time2roll]

joem789 wrote:
But my biggest question there would be how to connect a solar charge controller to the existing battery while leaving the 12V camper wiring connected for use? Does the controller basically go in between the batteries and the controller? Or does it all just hook together onto the battery?

Solar connects direct on the battery. NO other changes needed.

Controller will have two terminals to connect the panel and two separate terminals to connect to the battery. Controller close to the battery for best results.

Before:
Battery ---> RV

After:
Panels ---> Controller ---> Battery ---> RV



(load terminals are generally not used for RVs)

[Muddydogs]

Solar controller hooks to the battery posts along with anything else hooked to the posts. No need to unhook anything as all you are doing is charging the batteries.