Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
 

Go Back   Montana Owners Club - Keystone Montana 5th Wheel Forum > MOC Technical Forums > Solar, Charging Systems, Batteries and Electrical
Click Here to Login

Reply
 
Thread Tools Search this Thread Display Modes
 
Old 10-14-2012, 05:46 AM   #1
Alwims
Montana Master
 
Join Date: Aug 2010
Location: Wheatland
Posts: 675
M.O.C. #10623
Question about my solar setup

As I set right now, I'm running 2 Uni-Solar PV128 watt panels in series into a Morningstar TS MPPT 60 controller to 4, 6 volt golf cart batteries. I need some advice from you folks running the Uni-Solar panels. I have room on my roof for 3 more PV68 panels. How would you recommend I wire them? At the moment, I'm only going to add 2 PV68 panels and I figure I'll wire one of each to the 2 PV128 panels in series and run the 2 sets parallel to the controller. How would I wire the 3rd PV68 if I decide to add it? I hope this makes sense.
 
Alwims is offline   Reply With Quote
Old 10-14-2012, 09:02 AM   #2
7.3Ford
Montana Master
 
7.3Ford's Avatar
 
Join Date: Oct 2009
Location: Indian Land
Posts: 1,142
M.O.C. #9808
Alan,

Anything in parallel has to match. If you want to put three more 68W on, you need to put the one 68W and 128W in series, then parallel the two sets. You can then put the last 68W in series with the two parallel sets.


__________________
2015 Montana 3611RL - 2020 RAM 3500 SRW 4X4
John Walker, Indian Land, SC
Blog https://RoVIngWalkers.blogspot.com/
7.3Ford is offline   Reply With Quote
Old 10-14-2012, 09:16 AM   #3
Alwims
Montana Master
 
Join Date: Aug 2010
Location: Wheatland
Posts: 675
M.O.C. #10623
That's kind of what I was thinking, but I just wanted to hear it from the experts. I finally got my controller hooked up and working perfect. Had trouble with getting it shipped, long story. Haven't seen anything over 245 watts yet, but it's been mostly cloudy since I hook everything up. I'm looking forward to my pair of 68's I ordered yesterday getting here this week. Thanks
Alwims is offline   Reply With Quote
Old 10-21-2012, 03:37 AM   #4
Alwims
Montana Master
 
Join Date: Aug 2010
Location: Wheatland
Posts: 675
M.O.C. #10623
[s]I've been thinking, reading, and figuring, etc. Things my wife says I shouldn't do, but that's another topic all together. Since I would be well under the MPPT 60's voltage Voc limit, would it make more sense to wire all the panels in series, I'm only talking about the 2 128's and the 2 68's at this time. The 68's got hung up in shipping and should be here tomorrow so it has given me lots of time to think.[/s]

Never mind, figured it out going to wire per my original post in this thread.
Alwims is offline   Reply With Quote
Old 10-22-2012, 02:22 PM   #5
7.3Ford
Montana Master
 
7.3Ford's Avatar
 
Join Date: Oct 2009
Location: Indian Land
Posts: 1,142
M.O.C. #9808
Hi Alan,

I have wired them both ways, can't says as I have seen any difference. Unless you live down South, 245 Watts this time of year is good.

I think Greg, read somewhere the 40 to 50 volts is optimum for 12 volts systems.


__________________
2015 Montana 3611RL - 2020 RAM 3500 SRW 4X4
John Walker, Indian Land, SC
Blog https://RoVIngWalkers.blogspot.com/
7.3Ford is offline   Reply With Quote
Old 10-23-2012, 03:18 AM   #6
Alwims
Montana Master
 
Join Date: Aug 2010
Location: Wheatland
Posts: 675
M.O.C. #10623
Thanks a lot John. Now you've confused the heck out of me. We are in South South South Texas. I can see Old Mexico out of my living room window. What does living South have to do with whether I wire them Series or Parallel?
Alwims is offline   Reply With Quote
Old 10-23-2012, 03:51 AM   #7
dieselguy
Montana Master
 
dieselguy's Avatar
 
Join Date: Feb 2005
Location: Haysville
Posts: 4,261
M.O.C. #3085
I think he was refering to your location as in angle of suns rays and maybe clearness of the days ... not parallel or series.
dieselguy is offline   Reply With Quote
Old 10-23-2012, 04:14 AM   #8
Alwims
Montana Master
 
Join Date: Aug 2010
Location: Wheatland
Posts: 675
M.O.C. #10623
I believe you're correct, after rereading the statement. My bad. Need more coffee.
Alwims is offline   Reply With Quote
Old 10-23-2012, 05:51 AM   #9
Gkerlin
Montana Master
 
Join Date: Feb 2012
Location: Beaufort
Posts: 545
M.O.C. #12221
Quote:
quote:Originally posted by 7.3Ford

Hi Alan,

I have wired them both ways, can't says as I have seen any difference. Unless you live down South, 245 Watts this time of year is good.

I think Greg, read somewhere the 40 to 50 volts is optimum for 12 volts systems.


John is right. I can't remember where I read it now or I'd post the link, but for the Tristar MPPT on a 12v system the most efficiency is gained if your are running in the 40-50v range on the pv side. I don't recall if that was for all brand controllers or just the Morningstars. I think it was the latter.

Obviously this assumes that you are using correct wiring sizes and all other things considered. It was just a sweet spot for the controller. Above or below that 40-50v spot some energy is lost in conversion. For our purposes I don't know how much that would really matter or factor into my design considerations, but just one more piece of info.

Having a128 & 68 in series is right about where you want to be anyway. That's around 49v

If you go with the third 68 and wire it in series with the 2 parallel strings as John mentioned, it only adds 16v to that equation anyway. I'd much rather have the extra panel and take the slight theoretical loss of efficiency. You'll still be generating more power with it.
Gkerlin is offline   Reply With Quote
Old 10-23-2012, 07:53 AM   #10
Alwims
Montana Master
 
Join Date: Aug 2010
Location: Wheatland
Posts: 675
M.O.C. #10623
Wire sizing isn't a problem as I learned a long time ago that bigger is better when working with DC voltage. I built a junction box and am running as short a run as possible of the 10 gage wire from the panels to my junction box, 4 gage from the junction box on the roof to the MPPT controller and 4 gage from the MPPT to the batteries. 4-0 gage everywhere else. Unfortunately the 3rd 68watt panel is going to have to wait as I have run out of money. As a mater of fact, we are so broke that if it took a nickle to fly around the world, we'd have to walk. My $1000 solar system turned into $2000 + real quick.

My wife looked at me and said, "why are you fretting, this happens everytime you take on a progect like this" Why does she always have to be right???????
Alwims is offline   Reply With Quote
Old 10-23-2012, 02:11 PM   #11
7.3Ford
Montana Master
 
7.3Ford's Avatar
 
Join Date: Oct 2009
Location: Indian Land
Posts: 1,142
M.O.C. #9808
Quote:
quote:Originally posted by Alwims

Wire sizing isn't a problem as I learned a long time ago that bigger is better when working with DC voltage. I built a junction box and am running as short a run as possible of the 10 gage wire from the panels to my junction box, 4 gage from the junction box on the roof to the MPPT controller and 4 gage from the MPPT to the batteries. 4-0 gage everywhere else. Unfortunately the 3rd 68watt panel is going to have to wait as I have run out of money. As a mater of fact, we are so broke that if it took a nickle to fly around the world, we'd have to walk. My $1000 solar system turned into $2000 + real quick.

My wife looked at me and said, "why are you fretting, this happens everytime you take on a progect like this" Why does she always have to be right???????
Alan,

Don't forget you will get 30% of cost back on your IRS taxes. My Solar cost was $2,155 and I got $647 off of the taxes I owed. You need to fill out Form 5695. On first question (Ask you about primary residents), you answer NO, and go to page 2 and fill out the info.

Of course if you don't owe any taxes, you won't get any credit, but you can carry it over. I think you can only get $1,500 off of any one year, but you can carry the rest over to the next year.

I live in NC, and this time of the year, sun has moved South, so I don't see full power. Since the Montana sites in storage, I don't have exact numbers handy, but out of 544 Watts of panels, I see around 460 Watts. In Summer time I will see more than 544 Watts. Hope that helps.
__________________
2015 Montana 3611RL - 2020 RAM 3500 SRW 4X4
John Walker, Indian Land, SC
Blog https://RoVIngWalkers.blogspot.com/
7.3Ford is offline   Reply With Quote
Old 10-24-2012, 02:39 AM   #12
Alwims
Montana Master
 
Join Date: Aug 2010
Location: Wheatland
Posts: 675
M.O.C. #10623
I was just looking at the taxes part of all this yesterday and I thought I saw you say in another thread to answer no to the first question. So if we are due a refund we don't get the 30%? Don't ya just love our federal gov? Seems like our government needs to learn what the word "credit" means............in more ways than one. Well gota go put the 2 68's up on the roof, too windy yesterday.
Alwims is offline   Reply With Quote
Old 10-24-2012, 03:14 AM   #13
Gkerlin
Montana Master
 
Join Date: Feb 2012
Location: Beaufort
Posts: 545
M.O.C. #12221
Quote:
quote:Originally posted by Alwims

I was just looking at the taxes part of all this yesterday and I thought I saw you say in another thread to answer no to the first question. So if we are due a refund we don't get the 30%? Don't ya just love our federal gov? Seems like our government needs to learn what the word "credit" means............in more ways than one. Well gota go put the 2 68's up on the roof, too windy yesterday.
Now calm down there buddy and don't get in an anti government uproar

You can claim the credit.

The first question is just asking if it was for your main home and eliminates one specific credit. You'll go to part two and add your solar costs on line 15 and calculate your credit on line 20.

Remember to add up all of your costs... Wiring, controllers, panels etc. Any thing used in the installation.

And a credit is a credit... If you are due a refund your refund will only be bigger.

For instance. If your system cost $2,000 then your credit will be $600. That's $600 off of your tax liability. When you do your taxes and take all of your deductions and exemptions etc... and get to the final line where you calculate taxes... The $600 will come off that number. If you don't owe $600 the excess will roll over to the next year and you can take it off of your taxes then.

Some round numbers For instance: Lets say your calculated tax liability is $5,000. Lets also say you've had $6,000 withheld thru out the year. That means you would be getting a $1,000 refund.

But now since you get the solar credit - that is taken off of the $5,000 tax liability and instead your liability is $4,400. You still paid in $6,000 So you get $1,600 refunded.
Gkerlin is offline   Reply With Quote
Old 10-24-2012, 08:52 AM   #14
Alwims
Montana Master
 
Join Date: Aug 2010
Location: Wheatland
Posts: 675
M.O.C. #10623
Oh, ok, Since you explaned it that way, I feel much better now. Just got finished installing the 2 68's and now it's Miller Time or as the wife says, Ice Tea Time. Oh well I like both equally well. Sure is hot down here in the RGV, 92° while I was up on the roof.
Alwims is offline   Reply With Quote
Old 10-24-2012, 09:25 AM   #15
Gkerlin
Montana Master
 
Join Date: Feb 2012
Location: Beaufort
Posts: 545
M.O.C. #12221
Wow... 92. Did they go up ok? I waited till I got a cool day to put mine up as I heard the plastic really sticks to the black mastic as it gets hotter.

So your set up for now is going to be a 128 + 68 in series and two strings like that in parallel correct?

I really think you are going to love them. Mine was putting out more power than I really needed so far but I'm sure I'll figure out ways to still run my batteries down
Gkerlin is offline   Reply With Quote
Old 10-24-2012, 10:25 AM   #16
Alwims
Montana Master
 
Join Date: Aug 2010
Location: Wheatland
Posts: 675
M.O.C. #10623
Actually it got up to 92° before I got done. It was in the low 80's when I started. I did a bunch of sealing while I was up there. I learned to keep the panels cool with the first set so the plastic comes off clean. "So your set up for now is going to be a 128 + 68 in series and two strings like that in parallel correct?" Yes, correct. We already love them.

We've been running all the DC in the trailer off the battery bank for a while now, (I completely unplugged the onboard battery charger), and would go into absorb mode around 1pm everyday. We went into absorb mode at 11am today, about an hour after I flipped the switch on the new setup. Can't wait for my inverter to get back from the manufacturer for a warranty problem.

Most folks don't know how good it feels to know that if the grid in this country fails, we can a least survive with some semblance of normalcy. We are not survivalists, but strong believers in the old saying, "If you fail to prepare, you prepare to fail.

Alwims is offline   Reply With Quote
Old 10-24-2012, 10:57 AM   #17
Gkerlin
Montana Master
 
Join Date: Feb 2012
Location: Beaufort
Posts: 545
M.O.C. #12221
I hear you... We live on the Atlantic Coast and last year had to live in the RV for a few days after Hurricane Irene when our power was wiped out.
Gkerlin is offline   Reply With Quote
Old 11-03-2012, 06:25 AM   #18
Alwims
Montana Master
 
Join Date: Aug 2010
Location: Wheatland
Posts: 675
M.O.C. #10623
My solar system is up and working perfect. Now comes the hard part, figuring out this tax rebate thing. I know I can file the sales tax I paid, but what about shipping? I've been all over the Gov site and can't seem to find that answer. Any help?
Alwims is offline   Reply With Quote
Old 11-03-2012, 06:29 AM   #19
Gkerlin
Montana Master
 
Join Date: Feb 2012
Location: Beaufort
Posts: 545
M.O.C. #12221
All costs related to the purchase is part of your final cost. That includes parts, shipping, taxes, etc. Just don't deduct the taxes elsewhere.

If you paid anyone for labor that is part of the cost as well.

FYI my day job is an accountant.
Gkerlin is offline   Reply With Quote
Old 11-03-2012, 06:40 AM   #20
Alwims
Montana Master
 
Join Date: Aug 2010
Location: Wheatland
Posts: 675
M.O.C. #10623
Labor was all me. You could send me a consulting invoice, but please don't. Thanks again for the info.
Alwims is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Solar question Ozz Solar, Charging Systems, Batteries and Electrical 9 01-04-2015 01:41 PM
Solar Question Exnavydiver Sitting around the Campfire 5 05-11-2014 04:19 PM
Solar Question K&Gs3400RL Solar, Charging Systems, Batteries and Electrical 3 07-01-2012 07:45 PM
Solar question boje Boon-docking 2 07-22-2011 10:13 AM
Check out this Solar Setup TheCoachPotatoes Boon-docking 7 02-08-2011 06:03 AM

» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3
Disclaimer:

This website is not affiliated with or endorsed by Montana RV, Keystone RV Company or any of its affiliates. This is an independent, unofficial site.


All times are GMT -6. The time now is 06:55 PM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.