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Old 24-09-2012, 22:06   #1
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Solar panel output

Hey all, just wondering if someone can give me an idea about solar panel output. I have three 85W solar panels all connected to an amp meter, from there it goes into the solar regulator which then flows into the batteries. Problem is that im only getting about 2 amps out of all three panels in full overhead sun.

i know the panels are about 20 years old, and im thinking they may be past their use by date. Anyone who may be able to give some insight into this is most welcome. Thankyou, Luke. SV Catalpa
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Old 24-09-2012, 22:11   #2
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Re: Solar panel output

How are the panels wired? Serial or Parallel? Do you have any specs on the panels especially their working voltage? What kind of charge controller? What is the state of the battery charge when you are measuring the amperage?

Sum

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Old 24-09-2012, 22:28   #3
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Re: Solar panel output

panels are wired in parallel, max panel voltage is 20, then runs to a standard amp meter, then to a Solar Regulator. Batteries are anywhere from 70 to 100% charged. I thought the amount of amps being put in to the batteries would vary depending on the state of charge, but it keeps the standard 2 amp rate all the time. i can hear the regulator cutting in and out occasionally as well.
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Old 24-09-2012, 22:29   #4
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Re: Solar panel output

the working voltage is 12.
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Old 24-09-2012, 22:34   #5
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Re: Solar panel output

You can test the panels with a good multimeter that has a clamp-on current meter. Disconnect the panels from everything so that all you have are the leads from one panel (or the terminal blocks on the panel if that is how they are configured). Put your multimeter on DC Volts and read the voltage (in full sun) across the terminals. This will give you the open circuit voltage. If these are 36-cell panels (most likely for 85W, but could be elsewise) you should see something in the 20-22V range.

Cover the panel with something so that it has no light (none!). Short the wires together, then put your clamp-on ammeter on the shorted leads. Remove the cover so that the panel is in full sun. Measure the current. Again, if they are 36-cell panels you should probably have something like 5A. Re-cover the panel to re-connect the panel.

That's the easy testing, can tell you pretty quickly if the panels have basic function. After that you have to put an actual load on the panels to see if they actually put out power. You could connect them direct to the battery (bypass the controller) if you have a way to measure current. If they charge at a higher current that way then either a) the controller is the problem or b) the batteries are fully charged (or the controller thinks so). A short test like this should not be a problem for the batteries.

Is there a diode between the controller and the batteries? That can cause 0.5-1.5V drop and fool the controller.

Lastly, if your panels have bypass diodes that are not protected from reverse polarity (at they age they likely weren't), and were ever connected reverse polarity without a fuse in the line then the diodes could be damaged and you won't get much out of them (a study of small village power systems in Thailand found 18 out of 31 systems were not working after installation because of this one problem Bypass Diode Failure).
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Old 24-09-2012, 22:38   #6
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Re: Solar panel output

Quote:
Originally Posted by Catalpa1 View Post
panels are wired in parallel, max panel voltage is 20, then runs to a standard amp meter, then to a Solar Regulator. Batteries are anywhere from 70 to 100% charged. I thought the amount of amps being put in to the batteries would vary depending on the state of charge, but it keeps the standard 2 amp rate all the time. i can hear the regulator cutting in and out occasionally as well.
It should vary especially down at the 70%. How many batteries, voltage (1 or 2 12 volt or 6 volt in series or more than one bank)? Are you sure the batteries are good? No bad cells? They charge by other means? Have you disconnected the panels and tried one at a time.

It sounds like the controller might not even be a PWM but an older on/off type. Still the panels should be putting out more than that.

Hopefully someone will hit on the answer for you,

Sum

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Old 24-09-2012, 23:04   #7
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Re: Solar panel output

Just to add a little more to the discussion, I have panels fitted also and found a cable joint had corroded, a new joint solved that and I later bought a new MCCP controller and that made a noticable difference.
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Old 26-09-2012, 12:42   #8
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Re: Solar panel output

Thanks for your input guys, found it really helpful. im going to follow all your advice to check them, but im thinking i may just upgrade the whole system. I've been slowly refitting the boat anyways and it would be nice to know that I'll have the power there when i need it.
Thanks again for all your help, I'll let you know how it all goes...
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Old 26-09-2012, 12:55   #9
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Re: Solar panel output

A very simple test is to put a ~ 50-100 watt bulb on each panel, one at a time. You can tell by the bulb's apearance, though adding an ammeter to the circuit is better. I've done this.

You really should be seeing 4-15 amps total, depending on the variables (shade, SOC). I have 2x85.
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