RV Trip Planning Discussions

Go Back   iRV2 Forums > RV SYSTEMS AND TECHNOLOGIES FORUMS > Going Green
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
 
Thread Tools Search this Thread Display Modes
 
Old 02-21-2015, 09:22 AM   #1
Senior Member
 
Join Date: Jun 2004
Posts: 1,114
Mixing solar panels

I am in the process of installing solar on my new MH. I don't full time but do boondock while travelling. We're pretty frugal with power usually keeping the max down to about a 12 amp draw during the evening for about 3 hours + mostly just the minimum level during the daytime. Don't run the microwave or the coffee pot off 12 volts. Probably less than 50 Ah total per day. Also have Honda 2000EU which I don't mind running occasionally. Anyway on to the solar question. I was looking at the Tracer 40A mppt controller but now thinking about using the Midnite Solar Kidd controller due to quality\support concerns. I have two 160 watt panels 22.4 volt max. Can I add a 100 watt panel to utilize more the Kidd capacity? I ran the calc on the MS calculator and it says it's ok. The 100 watt panel I'm looking at has the same Voc and Vop parameters as my 160 watt panels. Should I run all three in parallel or series?
__________________

__________________
2014 Southwind 32VS
2013 Nissan Xterra PRO-4X
PbdBlue is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 02-21-2015, 09:35 AM   #2
Community Moderator
 
CountryFit's Avatar


 
Join Date: Sep 2011
Location: Between the Oceans
Posts: 6,499
Blog Entries: 4
batterypro is more authoritive on this, i would do 3 paralell. if you go with serial the current will be limited by the lowest watt one thus you are losing the two higher panels' full capacity.
__________________

__________________
Steven & Polly
2000 Country Coach Intrigue 40'
2014 Ford C-Max Energi
CountryFit is offline   Reply With Quote
Old 02-21-2015, 02:24 PM   #3
Senior Member
 
Join Date: Jun 2004
Posts: 1,114
Quote:
Originally Posted by CountryFit View Post
batterypro is more authoritive on this, i would do 3 paralell. if you go with serial the current will be limited by the lowest watt one thus you are losing the two higher panels' full capacity.
I'm thinking parallel also if for no other reason than to reduce shading effects but does series have an effieciency advantage other than wire size?
__________________
2014 Southwind 32VS
2013 Nissan Xterra PRO-4X
PbdBlue is offline   Reply With Quote
Old 02-21-2015, 03:16 PM   #4
Senior Member
 
BatteryPro's Avatar
 
Join Date: Jan 2015
Posts: 344
Never Series Connect Different Size PV Solar

Quote:
Originally Posted by PbdBlue View Post
....I have two 160 watt panels 22.4 volt max. Can I add a 100 watt panel to utilize more the Kidd capacity? I ran the calc on the MS calculator and it says it's ok. The 100 watt panel I'm looking at has the same Voc and Vop parameters as my 160 watt panels. Should I run all three in parallel or series?
Hi,

If the Vmp of different size solar modules is close, I usually specify 0.5 volts or less, then they will work together fairly well in parallel. What you should never do is put different size solar modules in series. The lowest current module will act as a load to the higher current modules in that string.


Quote:
Originally Posted by PbdBlue View Post
I'm thinking parallel also if for no other reason than to reduce shading effects but does series have an effieciency advantage other than wire size?
The primary benefit of series wiring is that higher voltage means less loss for a given power. This means you can use smaller wire which costs less and is easier to run. However, MPPT charge controllers are less efficient converting high voltage than lower voltage. So while wire loss may be less, conversion losses will be higher. See the attached chart. Notice how different Wattage modules affect efficiency? Now notice that the higher voltage you use, the lower the efficiency across the entire power range.

So if you use the right size wire, lower voltage, parallel connections will perform better.

Larry
Attached Thumbnails
Click image for larger version

Name:	Screen Shot 2015-02-21 at 3.02.59 PM.png
Views:	175
Size:	80.0 KB
ID:	86669  
__________________
I have a vast knowledge about PV solar, batteries and inverters. I'll try to provide the best answer if I know it and hopefully correct some "Campfire" talk. Full-time 1999-2004. Part time now. '92 Hawkins, 360AH Lithium Battery, 1480 Watts PV solar.
BatteryPro is offline   Reply With Quote
Old 02-21-2015, 04:23 PM   #5
Senior Member
 
Join Date: Jun 2004
Posts: 1,114
Quote:
Originally Posted by BatteryPro View Post
Hi,

If the Vmp of different size solar modules is close, I usually specify 0.5 volts or less, then they will work together fairly well in parallel. What you should never do is put different size solar modules in series. The lowest current module will act as a load to the higher current modules in that string.




The primary benefit of series wiring is that higher voltage means less loss for a given power. This means you can use smaller wire which costs less and is easier to run. However, MPPT charge controllers are less efficient converting high voltage than lower voltage. So while wire loss may be less, conversion losses will be higher. See the attached chart. Notice how different Wattage modules affect efficiency? Now notice that the higher voltage you use, the lower the efficiency across the entire power range.

So if you use the right size wire, lower voltage, parallel connections will perform better.

Larry
Thanks. The panels match each other within 100 millivolts. The total Iop for the panels is about 23 amps. The run to the controller will be ~15 feet. Would 8 ga wire be a reasonable choice or should I jump down to 6 ga?
__________________
2014 Southwind 32VS
2013 Nissan Xterra PRO-4X
PbdBlue is offline   Reply With Quote
Old 02-21-2015, 07:01 PM   #6
Senior Member
 
Bumps's Avatar
 
Winnebago Owners Club
Join Date: Sep 2013
Location: FTer Class of 2015 Origin: Evergreen, Colorado
Posts: 1,560
Quote:
I was looking at the Tracer 40A mppt controller...
You may have a different experieince, but I tried two of the Tracer MPPT charge controllers and they both failed. They did fine while the RV was stationary, but did not tolerate road vibrations very well. I switched to the MorningStar TS-MPPT60 and have had no problems. \ken
__________________
Ken, Deb, & Gadget (WIT Club, FMCA, SKP, and grateful volunteers with Habitat for Humanity and SOWERs), traveling in a well-behaved 2005 Winnebago Vectra 40FD w/1100w solar, some gee-golly-whizbang, and a TRAILERED 2015 Cherokee TrailHawk toad.
Bumps is offline   Reply With Quote
Old 02-21-2015, 08:54 PM   #7
Senior Member
 
Join Date: Jun 2004
Posts: 1,114
Quote:
Originally Posted by Bumps View Post
You may have a different experieince, but I tried two of the Tracer MPPT charge controllers and they both failed. They did fine while the RV was stationary, but did not tolerate road vibrations very well. I switched to the MorningStar TS-MPPT60 and have had no problems. \ken
Read a lot. Quality and support after sale were big factors in my decision not to go with the Tracer.
__________________
2014 Southwind 32VS
2013 Nissan Xterra PRO-4X
PbdBlue is offline   Reply With Quote
Old 02-21-2015, 10:28 PM   #8
Senior Member
 
chboone's Avatar


 
National RV Owners Club
Ford Super Duty Owner
Join Date: Sep 2010
Location: Horse Town USA, CA.
Posts: 3,298
Here is some good reading on Solar, especially about STC and NOTC ratings.

AM Solar's Educational Pages for RV Solar Systems
__________________
1999 35 ft. Dolphin 5350, F53, Banks System, 5 Stars Tune, Air Lift Air Bags, Koni Shocks, Blue OX TruCenter, TigerTrak track bars F&R, Roadmaster 1-3/4" rear auxiliary sway bar, 2004 F450 Lariat Pickup 6.0 Diesel Crew Cab DRW, 4X4, GVWR 15,000, Front GAWR 6,000, Rear GAWR 11,000, GCWR 26,000, 1994 36ft Avion 5er, GVWR 13,700, 2,740 Pin Weight.
chboone is offline   Reply With Quote
Old 02-22-2015, 07:25 AM   #9
Senior Member
 
Join Date: Jun 2004
Posts: 1,114
Quote:
Originally Posted by chboone View Post
Here is some good reading on Solar, especially about STC and NOTC ratings.

AM Solar's Educational Pages for RV Solar Systems
Thanks. I already read that and it was helpful. I had a simpler solar setup on my old MH so this isn't my first go at it but the first with multiple panels and MPPT. Looking around it seems if I stick with the supplied MC4 connectors that it's difficult to find cables larger than 8 ga.
__________________
2014 Southwind 32VS
2013 Nissan Xterra PRO-4X
PbdBlue is offline   Reply With Quote
Old 02-22-2015, 11:42 PM   #10
Senior Member
 
chboone's Avatar


 
National RV Owners Club
Ford Super Duty Owner
Join Date: Sep 2010
Location: Horse Town USA, CA.
Posts: 3,298
Quote:
Originally Posted by PbdBlue View Post
Thanks. I already read that and it was helpful. I had a simpler solar setup on my old MH so this isn't my first go at it but the first with multiple panels and MPPT. Looking around it seems if I stick with the supplied MC4 connectors that it's difficult to find cables larger than 8 ga.
AM Solar cuts off the MC4 connectors, butt splices, and uses epoxy fill heat shrink for 10 ga on the roof. My panels didn't have MC4, just had a junction box each panel.
__________________
1999 35 ft. Dolphin 5350, F53, Banks System, 5 Stars Tune, Air Lift Air Bags, Koni Shocks, Blue OX TruCenter, TigerTrak track bars F&R, Roadmaster 1-3/4" rear auxiliary sway bar, 2004 F450 Lariat Pickup 6.0 Diesel Crew Cab DRW, 4X4, GVWR 15,000, Front GAWR 6,000, Rear GAWR 11,000, GCWR 26,000, 1994 36ft Avion 5er, GVWR 13,700, 2,740 Pin Weight.
chboone is offline   Reply With Quote
Old 02-23-2015, 09:28 AM   #11
Senior Member
 
Join Date: Jun 2004
Posts: 1,114
I can get 8 ga with MC4 connectors. The max current of the panels is 23A (which I doubt I will see very often if ever). I think 8 ga will probably be adequate.
__________________
2014 Southwind 32VS
2013 Nissan Xterra PRO-4X
PbdBlue is offline   Reply With Quote
Old 02-23-2015, 04:40 PM   #12
Community Moderator
 
CountryFit's Avatar


 
Join Date: Sep 2011
Location: Between the Oceans
Posts: 6,499
Blog Entries: 4
handybob recommends 6g between panels and controller and 4g from controller to batteries. Here his blog https://handybobsolar.wordpress.com/...ging-puzzle-2/
__________________
Steven & Polly
2000 Country Coach Intrigue 40'
2014 Ford C-Max Energi
CountryFit is offline   Reply With Quote
Old 02-23-2015, 05:25 PM   #13
Senior Member
 
BatteryPro's Avatar
 
Join Date: Jan 2015
Posts: 344
Handy for Bob and everyone to know

Quote:
Originally Posted by CountryFit View Post
handybob recommends 6g between panels and controller and 4g from controller to batteries.....
Contrary to what Bob or anyone says, the PV wire size and controller to battery wire size should always be calculated, not guessed at. To say one needs to use 6 AWG without knowing the voltage or distance is wrong.

If you are using a PWM only controller, you don't need two different sizes of wire. The current flowing through the whole circuit is the same at the battery as it is at the PV solar modules as it is at the controller. Likewise, the charge controller can be placed anywhere in the circuit because it is simply an on-off switch. While Bob has a passion for telling people what to do, it is important to know why.

For example, [moderator edit] a 327 Watt PV module. To run 30 feet and have less than 1% voltage drop, I can use 14 AWG wire! That is a tiny wire compared to #6. How do I do it? The operating voltage is at 54.7 volts and the current is at 6 amps. If someone told you to use 14 gauge wire for 327 Watts you would think that's WAY too small. (FYI, I never run any PV wire with less than #10)

Now, let's compare that to using 2 160 Watt CTI modules. That's 320 Watts. To have under 1% drop I would need to use #4 AWG. That's bigger than the "recommended" 6 gauge. Why? Because the PV modules are operating at 17.5 volts and 17.72 amps. A very big difference in the voltage and current.

So it should be clear that wire size should always be calculated, not guess at.
__________________
I have a vast knowledge about PV solar, batteries and inverters. I'll try to provide the best answer if I know it and hopefully correct some "Campfire" talk. Full-time 1999-2004. Part time now. '92 Hawkins, 360AH Lithium Battery, 1480 Watts PV solar.
BatteryPro is offline   Reply With Quote
Old 02-23-2015, 05:36 PM   #14
Senior Member
 
BatteryPro's Avatar
 
Join Date: Jan 2015
Posts: 344
What is the operating current (Imp) of each PV module?
What is the operating voltage (Vmp) of each PV module?
These are different than the Isc, short circuit current and Voc, open circuit voltage.

If you let me know I will show you some calculations.
__________________

__________________
I have a vast knowledge about PV solar, batteries and inverters. I'll try to provide the best answer if I know it and hopefully correct some "Campfire" talk. Full-time 1999-2004. Part time now. '92 Hawkins, 360AH Lithium Battery, 1480 Watts PV solar.
BatteryPro is offline   Reply With Quote
Reply

Tags
panel, solar



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Choice of solar panels tlaffourtit RV Systems & Appliances 2 02-18-2015 08:01 AM
2015 DS 4018: Solar Panels tomakat Newmar Owner's Forum 1 01-28-2015 06:24 AM
How to hard wire solar panels into RV electric Service Rockymntnman Fleetwood Owner's Forum 21 12-25-2014 04:51 AM
Solar Charging Controller for two portable panels SkiSmuggs Boondocking 3 09-05-2014 10:29 AM
"Stick-on" solar panels danes-on-tour RV Systems & Appliances 2 05-27-2014 12:08 PM

» Featured Campgrounds

Reviews provided by


All times are GMT -6. The time now is 02:54 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
×