Solar for RV

6 Posts
Apr 27, 2009 11:31 am
Solar for RV

I'm considering installing a solar system on a RV. I figure I use about 50ah a day. Our normal camping is from Friday afternoon to Sunday afternoon. So I figure should we have a cloudy weekend the batteries should catch up through the week. I also do have a Kipor 2000 generator for backup. I have 2 Interstate 27 batteries, 100ah per. What I'm thinking of starting with are 2 Kyocera 135 panels hooked series with a MPPT controller. I'm not sure which controller to go with. Either the Morningstar MPPT or the Blue Sky 3024iL (also open for other suggestions). What is everybody thought on this setup?
 
578 Posts
Apr 27, 2009 12:13 pm
Re: Solar for RV

2 130 will be too much for the sunsaver mppt.

any controller 30a or higher should be fine on that array.

kyo 135 will have the connectors to wire up in series nicely, but you will have to buy an extension. something like this, that gets cut in half by the user. 

http://store.altestore.com/Cables-Wiring/Wiring-For-Solar-Panels/50-MC2-Connector-10-AWG-MaleFemale/p5986/

if you go with the 130's, make sure you get appropriate wire and fittings for solar applications, such as pv wire or use-2/rhw-2, strain reliefs and fork terminals rated for the temp and voltage. 

we have that stuff here

http://store.altestore.com/Cables-Wiring/Wiring-For-Solar-Panels/c467/

and here
http://store.altestore.com/Cables-Wiring/Wire-By-The-Foot/c468

ask if you have other questions,  good luck with your project

james
altE staff

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
6 Posts
Apr 27, 2009 02:23 pm
Re: Solar for RV

Thanks
 
6 Posts
Apr 28, 2009 09:58 am
Re: Solar for RV

If I go with 2 KD135GX-LP panels and a Blue Sky SB3024iL controller with battery temp sensor.

Witch is better, panels hooked series or parallel to charge 2 100ah batteries hooked parallel on a 12V system?

If I go parallel what size wire should I run from combiner box to controller with about a 15' run?

Ken
 
19 Posts
Apr 28, 2009 11:50 am
Re: Solar for RV

If I go with 2 KD135GX-LP panels and a Blue Sky SB3024iL controller with battery temp sensor.

Witch is better, panels hooked series or parallel to charge 2 100ah batteries hooked parallel on a 12V system?

If I go parallel what size wire should I run from combiner box to controller with about a 15' run?

Ken

2 12v panels wired in series will give you 24v output.  3 panels wired in series is 36v, and 4 panels wired in series is 48v.

2 12v panels wired in parallel is 12v output.  3 panels wired in parallel is 12v output, and 4 panels wired parallel is still only 12v.  The difference is the amperage increases the more panels you wire in parallel.
 
6 Posts
Apr 28, 2009 01:08 pm
Re: Solar for RV

I was under the understanding that with the MPPT controllers you could input 24V and if hooked to 12V batteries the output would be 12 volt.

If I go with 2 KD135GX-LP panels and a Blue Sky SB3024iL controller with battery temp sensor.

Witch is better, panels hooked series or parallel to charge 2 100ah batteries hooked parallel on a 12V system?

If I go parallel what size wire should I run from combiner box to controller with about a 15' run?

Ken

2 12v panels wired in series will give you 24v output.  3 panels wired in series is 36v, and 4 panels wired in series is 48v.

2 12v panels wired in parallel is 12v output.  3 panels wired in parallel is 12v output, and 4 panels wired parallel is still only 12v.  The difference is the amperage increases the more panels you wire in parallel.
 
19 Posts
Apr 28, 2009 03:38 pm
Re: Solar for RV

I was under the understanding that with the MPPT controllers you could input 24V and if hooked to 12V batteries the output would be 12 volt.

Exactly what would be the reason for essentially wasting half of the output of your 24v array by allowing the controller to reduce the output to 12v?

It's one thing if you're stuck with used inexpensive 72v direct-to-grid panels and looking to use them to charge an off-grid 48v battery bank for example (which they were never intended for).  Then the loss may be deemed acceptable due to the cheap per watt cost of the panels.
But it's another thing entirely to intentionally waste your new panel's output by not correctly designing your system for the correct voltage of your battery bank.
 
578 Posts
Apr 28, 2009 03:51 pm
Re: Solar for RV

you can wire the two modules in series.  the controller (the blue sky mppt you mentioned) will down convert it for you.  it will save you on voltage drop.  that would be the way i would do it.  there is no advantage in your case to wire them in parallel.

james
altE staff

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
351 Posts
Apr 28, 2009 05:43 pm
Re: Solar for RV

Ken (nice name):
I am with James. Wire the panels in series for 24V.
Not only is there no advantage to wiring in parallel, in some lighting conditions it would be a distinct disadvantage.

I am happy to see that you are considering are going for temp sensor. I like them for all systems, but they are even more necessary in an RV situation.

Ken
 
19 Posts
Apr 28, 2009 07:38 pm
Re: Solar for RV

That's the reason why 12v panels typically put out 18v-24v at peak output.

A 24v array would be putting out upwards of 30v at peak output.

Again, that seems like an awful lot of wasted output to have a controller reduce it to 14v for a 12v battery bank.  Unless, of course, you're hooking up a dump load from the controller into a water heater or air heater.

And while we're on the subject....why spend 4 times the amount of money for a Xantrex C40 on a charge controller (Blue Sky SB3024iL) that is supposedly able to maximize voltage (MPPT) if you're just going to dump a bunch of excess voltage into the controller with a 24v array anyways?

It doesn't make sense....dollars or otherwise.
« Last Edit: Apr 28, 2009 07:59 pm by fred flintstone »
 
6 Posts
Apr 28, 2009 08:15 pm
Re: Solar for RV

So which way is better for me go go with?

2 135w panels hooked parallel with the 30a ProStar PMW to charge 12v battery bank

or

2 135w panels hooked series with the BS3024iL MPPT to charge 12v battery bank?

I'm looking to get the most from the system because I think that the 2 135w panels are at their limit to my needs and down the road I might have to add more panels but at the moment money is an issue and looking for a starting point. From what I've read MPPT work best in cold conditions and I won't be using it in the cold. This is just for summer camping 2 days a week.
 
220 Posts
Apr 28, 2009 11:17 pm
Re: Solar for RV

hi folks,

 first a plug for our hosts.. thanks AltE for providing this free forum for the community.

 because this is an exchange of ideas, opinions and hopefully a good tool for those looking for information on renewable energy,(these subject threads are searchable and archived for folks to reference for who knows how long) i see this thread could use some additional resources on the topic of these mppt controllers.

 there is  much written on the subject, but here is a link to a short 1000 word writeup on the subject from a respected guru of renewables with nothing to sell.

 and now let's here it for and from mr. richard perez!

http://www.sendspace.com/file/7sunr4

 the above file was copied without permission from the archives of homepower magazine.

http://www.homepower.com/home/

 ken: good approach here, trying to research things out first before making a choice.

 fred: have a closer look into mppt, even us old dogs can learn new tricks. you may find that this new(ish) technology leaves some of those other controllers in the stone age for certain applications. and is worth at least considering as an option

kind regards, dave
« Last Edit: Apr 28, 2009 11:18 pm by david ames »
 
19 Posts
Apr 29, 2009 12:52 am
Re: Solar for RV

Thanks, I looked into mppt controllers several years ago.  While they have their uses, they aren't the be-all end-all of PV controllers, and the excessive cost must be weighed against the added benefit.
In this instance, is roughly 4 times the cost for the mppt controller worth it over the non-mppt controller such as the Xantrex C40?  It certainly isn't to me, and you read the original poster stating that he wasn't going to be using the system during the times when an mppt controller would be a benefit, i.e. during the wintertime.  He's using the system during the summertime, so why oversell him what he doesn't really need, particularly when he already told you he's on a budget?

Telling people to buy more expensive hardware than they really need was the downfall of the solar movement in the 1970's.  I see that we haven't really learned much in the intervening 30 years, and it doesn't comfort me that things will necessarily go any better this time around.
« Last Edit: Apr 29, 2009 12:56 am by fred flintstone »
 
220 Posts
Apr 29, 2009 02:27 am
Re: Solar for RV

good,.. just trying to spread some info on the topic.
have never noticed anyone doing any of that hard sell around here. they seem to have a more like a just answering peoples questions and showing different options approach.

 ken, now this is only my opinion. for you, with this application any type of controller you choose that is within the needed rating will do the job just fine.

 two 135 watt modules will give you in the neighborhood of 100ah charge per day into 12 volt battery bank(with only a 4.5hour full rated sun day) we most likely will get more in the summer with a good eye on parking places.

 i might consider a larger battery bank and smaller array.

-just my thoughts here and open for debate.

kind regards, dave
 
6 Posts
Apr 29, 2009 07:11 am
Re: Solar for RV

Thanks guys for the help.

I think I will go with a PWM style controller and save a few bucks. I will also concider adding another group 27 battery.

My rough estimate of power usage is 40ah to 60 ah per day. I just installed a Trimetric battery monitor that way I will know what my usage will be. We went camping this past weekend and I had a problem with one of my batteries so I didn't get an accurate handle on what we use. With only the fridge running on gas for 2 days it dropped batteries to 60% and running a gen for hours I couldn't get above 65%. Once I swapped out the bad battery for a good one it went to FULL in minutes.

Thanks again.
Ken
 
1 Posts
Apr 29, 2009 01:23 pm
Re: Solar for RV

Great thread guys.

The energy for a charge controller is about equal once the minimum voltage is reached.  So, if you have 30V input, you will get 12V out and more current than if you have 15V input.  It is more of a question of "how fast do you want to recharge the batteries".  Voltage is the push, current is the energy (Amps is the measure of electrons past a point in a second, or something like that).  So, a higher voltage will give you more amps and a shorter charge time.  That is not always good, batteries live longer on a "trickle charge" than with a jolt of energy.  I would check the battery specs and see what the nominal charge current is, then look at the panels you are considering and review the Watts output (watt = volts x amps). 

Just more to consider.
 
4 Posts
Apr 29, 2009 06:19 pm
Re: Solar for RV

I just finished a instal on our horse trailer with liveing quarters. I went a little bigger than your thinking but we camp for weeks at a time and I didn't want to worry about power and I didn't want to listen to a generator. I'll try to post this link to a articule that I think you will find a great help.
Bob
http://docs.google.com/Doc?id=dcr9s9n5_126x8xdwf2&invite=215280009
 
19 Posts
Apr 30, 2009 11:33 am
Re: Solar for RV

I just finished a instal on our horse trailer with liveing quarters. I went a little bigger than your thinking but we camp for weeks at a time and I didn't want to worry about power and I didn't want to listen to a generator. I'll try to post this link to a articule that I think you will find a great help.
Bob
http://docs.google.com/Doc?id=dcr9s9n5_126x8xdwf2&invite=215280009

I'm about 1/4 way through your article and I just have to say....good job!  That and....methinks you may end up being persona non grata around these parts (and anywhere else solar power components are sold) LOL!  Unfortunate, but inevitable I suppose.
 
4 Posts
Apr 30, 2009 07:06 pm
Re: Solar for RV

Sorry I can't take the credit for this vary smart mans article. I can only follow instructions somewhat but I've read this several times and have garnered allot from it.
 I found this article after I purchased two Evergreen 210 watt panels and the Morningstar Trystar 45 control.
 We just got back from 10 days in a national forest in which we had two days of rain and several days we used the heater all night without any need of a generator.
 This system charges in overcast and even rain!
 I know it's a little overkill but I don't go camping with my horses in the middle of nowhere to sit and listen to a generator drone on for hours.
 This has been my first trial as I just got it installed but it seems to be doing everything I want it to do and allot more.
 I want to thank everyone at AltE for there advice and help with this project. Now all I have to do is convert everyone I go riding with.
 PS- The Trystar 45 control doesn't make any noise with these panels.
 THANKS
 Bob Baker
 
19 Posts
May 1, 2009 08:24 am
Re: Solar for RV

Thanks for the clarification.  I assumed that since your name was 'Robert' that you were the 'Handy Bob' who wrote the article.  No matter, great job linking to it.

So, according to 'Handy Bob's article, those two 135 watt panels should have no problem whatsoever running a moderate-sized RV off-grid.  The key seems to be:
1) Get a controller that can be set to 14.8 volts if needed for wet cell batteries.
2) Locate the controller as close as possible to the battery bank (and not above the RV fridge as is common).
3) Use big wire in your installation.....#6 or #8 ....the bigger the better.
4) Use 2 - 6 volt golf cart batteries wired in series to get 12v in your battery bank, batteries such as the Trojan T105, and follow the battery manufacturer's recommended charging voltage (14.8v for Trojan T105's)
5) Don't ever rely on the RV manufacturer's battery charger as they are underwired and underperforming junk.

There is plenty of other useful information in that article, I simply listed the highlights.  I encourage everyone interested in the subject of PV to read it.
 
351 Posts
May 1, 2009 03:13 pm
Re: Solar for RV

I don’t see why Fred thinks that  Handy Bob’s articles would be “persona non grata around these parts”. There is a lot of good info in them, but it has the danger of being mis-used.

Handy Bob has a disrespect of RV dealers/solar sellers around Quartzsite AZ, not of all people in the solar business. Fred seems to apply a similar disrespect to everyone in the solar business.

Solar systems in RV’s while being similar to residential systems, do have different aspects that you need to consider. And conversely, you cannot apply “what works best for RV’s” to all PV systems.

Golf cart batteries are the entry level batteries of the solar business.  They could even be called the bread and butter of the small system. But for larger systems, they are just training batteries.  There are a lot better batteries out there, particularly for larger stationary systems.

Charging at 14.8 is Trojan’s recommendation; it is not the gospel for every wet cell batteries. Interstate recommends a bulk charge setting of 14.4. 
Note that Handy Bob mentioned a battery temp sensor. While I like them for all installations, they are even more important in RV’s. And, if you are charging above 14.4 volts without one, you are living dangerously. The warmer the ambient conditions, the more important the sensor is. I’ve gotten to the point where I no longer consider them optional.

Wire sizing is important. I generally aim for 3 percent drop or less. It is also important to consider future upsizing of the system. I weigh the cost of going larger now vs. the cost of future rewiring.  But “bigger is not always better”.  #6 and #8 are SMALL wires with a marginal cost difference. Look at the price difference in a 1/0 and a 3/0  before saying bigger is better. Carte blanche oversizing wires can be a huge waste of money.

But the point that I really differ with these gentlemen on, is the value of the MPPT controller.  If you live (or RV) in an area with great solar conditions, you may not see great value in it.  But, where you will see the value of it is in less than optimal conditions. It shows gains in the hours before and after the peak sun period. If you have any type of overcast, marine layer, smoke, smog, dust, etc, that reduces the solar insolation, you can have a boost even during the peak sun hours. 

In my area, I usually see a summertime increase in production that is close to 10%.  Over in the fog belt (closer to the coast) it is closer to 15%.  We never get the 30% boost that the mfgs claim for wintertime, primarily because we don’t have subfreezing, crystal clear winter days. You can count the days below 40 degrees on one hand.  MPPT is not “only useful in winter”.

You do have to try to quantify what this increase is for a particular microclimate, and weigh the value of it. The best way to do that is install one on an existing system with known production and then compare the difference in monthly production.  In my area, it is a no brainer. Yes, it costs more. But it is a lot cheaper than increasing your array by 10%.

 
19 Posts
May 1, 2009 04:13 pm
Re: Solar for RV

No, I said HandyBob /may/ be persona non grata with an article like that.  The article can't be persona non grata because the article isn't a person.

This thread is about RV's so the wiring and battery choices I listed specifically apply to RV's.  (The concepts carry over to other photovoltaic systems however.)

If you read what I posted on controller voltage, you'd see that I specifically stated that 14.8v was what Trojan recommended, and that the proper voltage is what your battery manufacturer recommends, not what your controller manufacturer recommends.

As for mppt, if you read his article, he explains that increasing wire size delivers more volts to the batteries, rather than attempting to 'boost' voltage to the batteries via a costly mppt controller (and subsequent higher voltage array which results in more amperage not more proper charging voltage being delivered by the mppt controller), or by spending even more money for more panels to overcome the inefficiency of an underperforming system.

All in all, HandyBob explodes some popular current PV myths and fads, myths and fads that can be used by unscrupulous salespeople to pad their own wallets and sell people more hardware than they actually need....and have it all work at less than stellar efficiency to boot.
 
19 Posts
May 1, 2009 09:51 pm
Re: Solar for RV



Handy Bob has a disrespect of RV dealers/solar sellers around Quartzsite AZ, not of all people in the solar business. Fred seems to apply a similar disrespect to everyone in the solar business.



False.  For the record, HandyBob clearly states that he believes the majority of players (not just in Quartzsite) in the solar biz (RV or otherwise) are less knowledgeable than they portend to be, and more likely to simply parrot manufacturers dubious claims and figures, and more likely than not to simply push the hardware that will bring them the most revenue. And install it incorrectly or inefficiently.

I simply happen to agree with him.  That isn't "disrespect", its simply a observation of the industry.  Sadly I might add.
 
351 Posts
May 2, 2009 02:07 am
Re: Solar for RV

I do not know why you presume to have the right to lecture me on my English usage (or whatever the hell you want to call it.) 
“The article can't be persona non grata because the article isn't a person.”

Did you see the quotation marks around the phrase Huh
Just for your information, one of the proper uses of quotation marks is to signal unusual usage of a word or phrase.  If you are going to call someone on something, you better be right.

What a pompous, arrogant, north end of a southbound horse.
 
19 Posts
May 2, 2009 12:26 pm
Re: Solar for RV

I do not know why you presume to have the right to lecture me on my English usage (or whatever the hell you want to call it.) 
“The article can't be persona non grata because the article isn't a person.”

Did you see the quotation marks around the phrase Huh
Just for your information, one of the proper uses of quotation marks is to signal unusual usage of a word or phrase.  If you are going to call someone on something, you better be right.

What a pompous, arrogant, north end of a southbound horse.


LOL!  So lacking a valid argument on the subject and confronted with your distortions of HandyBob's article and distortions of my references to it, you resort to namecalling?  WTF?

Is that what happens also when one of the recipients of your purportedly great solar installations dares to question you on what you're doing (or done) and why?  Call them names and become defensive?  LOL!

As long as we're back on the subject of solar, maybe next time you install solar panels in cloudy, hazy, foggy, or otherwise sun obstructed locations you'll use thin film/amorphous panels which are capable of putting out close to their rated wattage even on cloudy days in ambient light instead of the higher priced panels and mppt controllers you love so much.  Ah, but thin film/amorphous panels and standard controllers using thick wire and "training batteries" (for new solar system owners) aren't near the money maker that all of the latest wiz-bang stuff is, eh?

Apparently, you're the exact kind of individual that HandyBob was referring to.  What a surprise.  Thanks for proving HandyBob's point.
 
109 Posts
May 4, 2009 02:35 pm
Re: Solar for RV

Hello Everybody!

Seems like we are getting a little more personal with the replies.  In order to make this board useful, we request that people do not make personal attacks.  When there are disagreements, sticking with facts/hard data is the best way to resolve the issue.

Thanks Guys!  Hopefully this should make this better for everyone involved. = )
 -Nick

AltE
"Making Renewable Do-able"
http://www.altEstore.com/
 
1 Posts
May 5, 2009 11:02 am
Re: Solar for RV

howdy from idaho. mr flinstone would you be so kind to email me at coaltrainhowdy @ gmail.com  thank you
 

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