Solar Charger

[Chris Jones]

I have a U Haul CT 13 and I am not sure if the Solar Charger is working. I know it can be tested, but how? This is the last wild in my CT I have everything else working. Any info on these would help me out because I have never used anything like this. Thanks

[cpaharley2008]

I'd unplug the battery and the electric to the trailer and put my meter to the leads to see if any current is flowing from the solar panel.

[Chris Jones]

So this thing should make power without a load? I'll give it a look as soon as I can find my meter. Thanks for the quick answer.

[cpaharley2008]

Yes it is always charging if subject to light, the controller regulates the output but it is always working in the daytime. If you know where the controller is you can test it there also.

[Chris Jones]

Originally Posted by cpaharley2008

Yes it is always charging if subject to light, the controller regulates the output but it is always working in the daytime. If you know where the controller is you can test it there also.

Well it has power coming to it and from it to the batterie box wires. But it does not put out enough to run any of the inside lights. I will put a batterie in there and see how it maintains the state of charge over time.

Thank you so much for the help.

[Thomas G.]

Chris, I found that my controller was bad and that the panel itself hardly put out anything.

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.

I replaced my panel with a 60 watt panel, which will do some serious charging. The original was only designed to prevent the battery from going stone dead when the trailer sat for a long time.

This place has pretty good prices on solar panels and controllers.

12 Volt Solar Panels

[cpaharley2008]

May only be a 15 watt battery maintainer panel. Pictures would help.

[Chris Jones]

Originally Posted by cpaharley2008

May only be a 15 watt battery maintainer panel. Pictures would help.

That's the controller. It clicks when I turn on lights without the batterie hooked up. Might be why it will not run any of the inside lights without a batterie hooked up because it wasn't designed as a stand alone unit. But if the sun is out I won't need lights on the inside anyway.

[Carol H]

Originally Posted by Chris Jones

Well it has power coming to it and from it to the batterie box wires. But it does not put out enough to run any of the inside lights. I will put a batterie in there and see how it maintains the state of charge over time.

Thank you so much for the help.

Chris I doubt if it was originally set up to run anything directly off of it. Solar panels are most often set up to recharge the battery with the lights running off the battery not directly from the panel.

I seem to recall though that original reading here once that the solar panels on the old U-hauls were actually very small 3 watt?? & not really meant to fully recharge the battery - only meant to avoid battery sulfation while the trailers sat at the rental lot.

If it is a 15 watt though it should be able to recharging the battery in full sun in the course of a day with no load on the battery or at least my old 15 watt panel did.

[Thomas G.]

Originally Posted by Carol H

Chris I doubt if it was originally set up to run anything directly off of it. Solar panels are most often set up to recharge the battery with the lights running off the battery not directly from the panel.

I seem to recall though that original reading here once that the solar panels on the old U-hauls were actually very small 3 watt?? & not really meant to fully recharge the battery - only meant to avoid battery sulfation while the trailers sat at the rental lot.

If it is a 15 watt though it should be able to recharging the battery in full sun in the course of a day with no load on the battery or at least my old 15 watt panel did.

It is way less than 15 watts. It is an amorphous cell which only produce about 5 watts per square foot when new.

[mmeyer]

Originally Posted by Thomas G.

It is way less than 15 watts. It is an amorphous cell which only produce about 5 watts per square foot when new.

I looked at the one I took off the VT the model /serial number starts with a 84 and ends with -15 which would likely indicate built in 1984 and 15 watts. CT 's may be different.
Michael J

[Thomas G.]

Originally Posted by mmeyer

I looked at the one I took off the VT the model /serial number starts with a 84 and ends with -15 which would likely indicate built in 1984 and 15 watts. CT 's may be different.
Michael J

Dunno. I know that when I tested the output of mine it was only a watt or two after 27 years.

[mmeyer]

Originally Posted by Thomas G.

Dunno. I know that when I tested the output of mine it was only a watt or two after 27 years.

When I feel better I will dig out my decade resistor box and do some measurements, I know it will charge 10 ah 12v gel cells.

[Thomas G.]

Here is a video that shows how to measure solar panel output.

Solar Panels - How to Test - AltE Video Tip - YouTube

[mmeyer]

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.

[Brian B-P]

Originally Posted by Thomas G.

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.

[Thomas G.]

Originally Posted by Brian B-P

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.

[Chris Jones]

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.