Solar Charger - Page 2 - Fiberglass RV

Thread Tools Search this Thread Display Modes
Old 01-04-2013, 05:17 PM   #15
Senior Member
mmeyer's Avatar
Name: Michael J
Trailer: U-Haul VT
Posts: 449
Figure I would just go "old school" and measure voltage through 3 or 4 precision resistors using the decade resistance box, from which I can calculate amps , graph it up and see what I get. Knowing amps and volts I can calculate watts. The panel does not have any open circuit voltage or short circuit amp data.

mmeyer is offline   Reply With Quote
Old 01-05-2013, 05:49 PM   #16
Senior Member
Brian B-P's Avatar
Name: Brian
Trailer: Boler (B1700RGH) 1979
Posts: 5,000
Originally Posted by Thomas G. View Post
To test the solar panel, disconnect the wires from the panel to the controller mounted on the side of the battery box. Attach an ammeter lead to each wire end while in full sun. That panel is about 5 watts, so you should get about 0.4 amps or so.
Tom, did you calculate 0.4 amps as 5 watts divided by 12 volts? That is not valid, because the panel output will only be 5 watts under and ideal load, and that's not your ammeter.
  1. Connect just an ammeter (which has nearly zero resistance) and you measure the short circuit current, at nearly zero voltage. The panel can't push this much current through any load; in full sun it should be significantly higher than 0.4 amps for a 5 watt panel.
  2. Connect just a voltmeter (which has nearly infinite resistance) and you measure the open circuit voltage, at nearly zero current. The panel can't push any current through a load at this voltage; in full sun it should be much higher than 12 volts for a "12volt" panel (about 20 V is typical).
  3. Connect the panel to a charged "12V" battery, check both the current flowing through the panel and battery and the voltage, then multiply current (in amps) by voltage (in volts) to get actual panel output power (in watts). A fully charged battery should be at a voltage which is reasonably close to ideal for a panel intended to charge 12V batteries; in full sun the panel should produce close to its rated output.

The later posted video may explain this, but I rarely bother with YouTube videos, and especially not on a wireless internet connection.

Update: I did try watching the video... a minute and a half before he said anything about testing, another minute to actually start (although they showed the panel specs - without explanation - during that time), and then it stalled. I'm guessing it might have been useful somewhere in the last three minutes.

1979 Boler B1700RGH, pulled by 2004 Toyota Sienna LE 2WD
Information is good. Lack of information is not so good, but misinformation is much worse. Check facts, and apply common sense liberally.
STATUS: No longer active in forum.
Brian B-P is offline   Reply With Quote
Old 01-05-2013, 05:54 PM   #17
Senior Member
Thomas G.'s Avatar
Name: Kinga DeRode
Trailer: For Sale Or Rent
Rooms to Let 50 Cents
Posts: 5,094
Originally Posted by Brian B-P View Post
Tom, did you calculate 0.4 amps as 5 watts divided by 12 volts? ...........
Yes, I recommended this as a quick and dirty test to see if it was putting out anywhere near the original amperage. My own UHaul panel only put out about 100 mA in full sun - that is when I decided to replace it.
UHaul and Burro owners, join the UHaul Campers on Facebook.
Thomas G. is offline   Reply With Quote
Old 01-05-2013, 06:03 PM   #18
Senior Member
Chris Jones's Avatar
Name: Chris
Trailer: U Haul CT 13
Posts: 240
Well I figured out that it might not have been putting out what it was supposed to. I washed the trailer today and it seems that the thick green layer of crud might have been keeping it from working very well. A good wash and hooked it to the group 29 and let it see what it can do.

Chris Jones is offline   Reply With Quote


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
Solar Trickle Charger & Dead Battery V'sGlassSleeper Problem Solving | Owners Helping Owners 11 03-19-2010 07:29 PM
Solar Panel Trickle Charger? Steve Dunkel General Chat 17 02-21-2010 12:42 PM
Solar Charger and Panels Frederick L. Simson Modifications, Alterations and Updates 109 08-11-2008 10:41 PM
Solar Powered Battery Charger Rich S Electrical | Charging, Systems, Solar and Generators 6 10-17-2006 09:19 AM
Solar charger questions Steve Rosenberg Care and Feeding of Molded Fiberglass Trailers 17 12-01-2005 01:00 AM

» Trailer Showcase


Janey B


Ben M
» Upcoming Events
No events scheduled in
the next 465 days.
» Virginia Campgrounds

Reviews provided by

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 04:12 AM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.