RV.Net Open Roads Forum: Tech Issues: Solar Panel Shadows and Bypass Diodes

RV Blog

  |  

RV Sales

  |  

Campgrounds

  |  

RV Parks

  |  

RV Club

  |  

RV Buyers Guide

  |  

Roadside Assistance

  |  

Extended Service Plan

  |  

RV Travel Assistance

  |  

RV Credit Card

  |  

RV Loans

Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Tech Issues

Open Roads Forum  >  Tech Issues

 > Solar Panel Shadows and Bypass Diodes

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 3  
Next
Sponsored By:
CA Traveler

The Western States

Senior Member

Joined: 01/03/2004

View Profile


Offline
Posted: 01/16/15 07:51pm Link  |  Quote  |  Print  |  Notify Moderator

The following data was collected from my 3x250W flat mounted solar panels on 1/16/15 in my storage area in the Phoenix area. The graph shows the significant transition as the sun just covers the 3rd rear most panel while the front 2 panels are in full shade. The Vmp is 92V for the 3 panels in series.

Prior to the transition the sun is covering 2/3rds of rear panel which is producing about 17V and the remaining section is in bypass mode as are the other 2 panels. Then at the transition the 3rd panel is producing its full power while the other 2 panels remain in bypass mode.

This shows an advantage of series panels with bypass diodes and an MPPT controller. For a compatible situation with parallel panels and PWM there would be no power for the batteries prior to the transition.

After the transition the graph shows the MPPT60 controller adjusting for Vmp to obtain maximum power to the batteries. Ie Array voltage is being reduced and array current is increased.

Solar Controller Graphs - Updated and date of test corrected
[image]


Storage area overview
[image]

Sun transition on the 3rd panel
[image]

* This post was last edited 04/15/15 12:32pm by CA Traveler *   View edit history


2009 Holiday Rambler 42' Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2014 Grand Cherokee Overland

Bob


pianotuna

Regina, SK, Canada

Senior Member

Joined: 12/18/2004

View Profile


Offline
Posted: 01/17/15 06:25am Link  |  Quote  |  Print  |  Notify Moderator

Hi CaTraveler,

Thanks for the information. What are the units on each graph?


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

CA Traveler

The Western States

Senior Member

Joined: 01/03/2004

View Profile


Offline
Posted: 01/17/15 06:51am Link  |  Quote  |  Print  |  Notify Moderator

Oops - The battery amps was showing on the wrong scale. Graph updated above and now showing time scale.

* This post was last edited 01/17/15 08:01am by CA Traveler *   View edit history

2oldman

NM

Senior Member

Joined: 04/15/2001

View Profile


Offline
Posted: 01/17/15 01:38pm Link  |  Quote  |  Print  |  Notify Moderator

Good post. Some of my panels in partial shade will partially shut down, others will completely shut down.

atreis

IN

Senior Member

Joined: 08/29/2005

View Profile


Offline
Posted: 01/18/15 06:54am Link  |  Quote  |  Print  |  Notify Moderator

Kyocera panels (and perhaps others?) have multiple bypass diodes that will allow portions of the panel to continue to operate when partly shaded. Many of the really cheap panels have no bypass diodes, or only have one for the whole panel.


2021 Four Winds 26B on Chevy 4500


brulaz

Ontario Canada

Senior Member

Joined: 02/27/2013

View Profile



Good Sam RV Club Member

Offline
Posted: 01/18/15 07:20am Link  |  Quote  |  Print  |  Notify Moderator

CA Traveler wrote:


...
This shows an advantage of series panels with bypass diodes and an MPPT controller. For a compatible situation with parallel panels and PWM there would be no power for the batteries prior to the transition.
...


Don't understand this statement.

When all panels are under full shade, what does parallel versus serially connected panels have to do with power output? Or bypass diodes?

EDIT: Never mind, I get it, finally. That one panel was initially not under full shade. Rather it was under partial shade allowing the bypass diodes to do their thing.

I understand that mppt can be better in full shade.

* This post was edited 01/18/15 08:00am by brulaz *


2014 ORV Timber Ridge 240RKS,8500#,1250# tongue,44K miles
690W Rooftop + 340W Portable Solar,4 GC2s,215Ah@24V
2016 Ram 2500 4x4 RgCab CTD,2507# payload,10.8 mpgUS tow

12thgenusa

Loveland, Colorado

Senior Member

Joined: 12/08/2009

View Profile



Good Sam RV Club Member

Offline
Posted: 01/18/15 07:49am Link  |  Quote  |  Print  |  Notify Moderator

I recently (before Christmas) went over to check my trailer in storage after a snow storm. Before I checked the panels I loaded up the electrical system and found that it would only produce about 91 watts. I went on the roof and found that one panel was completely snow covered and the other was about 1/3 to 1/2 covered. I swept off the snow and went back down to check production again. It was now at 198 watts. This is about spot on for my panels currently mounted flat, with 5 degree roof slope to the South at about 30 degrees F. Panels are wired in parallel.

Here is a nice tutorial on bypass diodes. Their primary function is to prevent hot spots and damage to the panels, but a nice benefit is partial production in partial shade.


2007 Tundra DC 4X4 5.7, Alcan custom rear springs, 2009 Cougar 245RKS, 370 watts ET solar,
Rogue MPT-3024, 440 AH GC2 bank, ProWatt 2000,100% LED lighting


pianotuna

Regina, SK, Canada

Senior Member

Joined: 12/18/2004

View Profile


Offline
Posted: 01/18/15 07:53am Link  |  Quote  |  Print  |  Notify Moderator

Hi brulaz,

If the panels have bi pass diodes and are poly or amorphous then some power is going to go to the controller.

For example, at solar noon in June in rain, I sometimes get 3 amps of output from the controller. Under perfect conditions with loads on the battery bank I get 17 amps. The panels are in series parallel for a vmp of 33 volts. This allows the controller to output some current 30 minutes after sunrise.

mena661

Southern California

Senior Member

Joined: 03/21/2009

View Profile


Offline
Posted: 01/21/15 04:18pm Link  |  Quote  |  Print  |  Notify Moderator

Missed this one entirely. Great post!


2009 Newmar Canyon Star 3205, Ford F53 V10
Trojan L16 6V's 740 Amp-hours


jrnymn7

Ontario

Senior Member

Joined: 12/18/2013

View Profile



Posted: 01/21/15 04:27pm Link  |  Quote  |  Print  |  Notify Moderator

CA Traveler said;

"For a compatible situation with parallel panels and PWM there would be no power for the batteries prior to the transition."

Is this an accurate statement? Wouldn't the panels just put out less amperage?

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 3  
Next

Open Roads Forum  >  Tech Issues

 > Solar Panel Shadows and Bypass Diodes
Search:   Advanced Search

Search only in Tech Issues


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:




© 2022 CWI, Inc. © 2022 Good Sam Enterprises, LLC. All Rights Reserved.