Help interpreting Solar info please

Submitted: Sunday, Jan 01, 2006 at 21:23
ThreadID: 29297 Views:5705 Replies:5 FollowUps:4
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Howdy all, I am looking at buying a Uni-Solar 128w Flexible Laminate Solar Panel with the following electrical characteristics

Rated Power: 128 W
Nominal Voltage: 24 V
Peak Power: 128 W
Peak Voltage: 33 V
Peak Current: 3.88 A
Open Circuit Voltage: 47.6 V
Short Circuit Current: 4.8 A

it is from the States hence the 24V. I have been buying bits and pieces as I go along to spread costs, I have already bought a PowerTech 20A Solar Charge Controller (http://www.jaycar.com.au/productView.asp?ID=MP3129) with the following characteristics,

Specifications
*Battery Voltage: 12V
*Maximum PV panel open circuit voltage: 26V
*Continuous load/charge current: 20A
*Maximum charge/load current (5 mins): 25A

My question is that the open circuit voltage on the panel is greater than that of the charge controller, so my charge controller won't work with it? But i am confused as I got a 20 Amp charge controller that can easily handle a 128 12 volt panel? I just don't understand why my charge controller is to small for a 128 Volt panel. I guess it's because the regulator is a 24 Volt regulator, so if it was a 12 Volt regulator my charge Controller would be fine? If so is there any way I can modify the panel to work with my charge controller? Thanks alot.
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Reply By: Michael B - Sunday, Jan 01, 2006 at 21:41

Sunday, Jan 01, 2006 at 21:41
Hey Lunar,

And I thought that I had problems.......If u get yours sorted, give me a answer to my question........

Michael B (SA)
AnswerID: 146241

Reply By: hl - Monday, Jan 02, 2006 at 06:47

Monday, Jan 02, 2006 at 06:47
That's a big mother of a panel!
And your regulator is not suitable as the no load voltage will be far too high.
You need a regualtor designed for a 24V panel, unless that panel can be wired to provide 12V output.
Cheers
AnswerID: 146274

Reply By: Footloose - Monday, Jan 02, 2006 at 08:36

Monday, Jan 02, 2006 at 08:36
What are you trying to power with the solar power ? If it's a 12v battery then get a panel that supplies 12v.
AnswerID: 146287

Follow Up By: Lunar - Monday, Jan 02, 2006 at 15:52

Monday, Jan 02, 2006 at 15:52
yeah that's the original intent but this one is REAL cheap and u can role it up so ideal for camping, was hoping to be able to modify it for use over here, even if I had to spend another 100 or so to modify it it would still be a very good deal.
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FollowupID: 399848

Reply By: Mike DiD - Monday, Jan 02, 2006 at 21:20

Monday, Jan 02, 2006 at 21:20
Solar Panels are essentially constant current sources - whether you connect it to a 24 volt battery or a 12 volt battery, you will get about 3.5 amps from it when in direct sunlight. (Into a 1 (one) volt battery you will get abt 4.5 amp)

However if you connect a 24 volt panel to a 12 volt battery you are only getting half the power of it - so it's only going to be as effective as a 12 volt 60 watt panel.

Mike
AnswerID: 146348

Follow Up By: Lunar - Monday, Jan 02, 2006 at 23:01

Monday, Jan 02, 2006 at 23:01
Thanks Mike, sounds like I'm back to the drawing board :(.
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FollowupID: 399895

Reply By: Pajman Pete (SA) - Friday, Jan 06, 2006 at 16:44

Friday, Jan 06, 2006 at 16:44
What about one of these:

24 Volt Solar Regulator

Charge two batteries in series at 24V and draw your power from them in parralel at 12V. You will need some diodes in the wiring but any sparky should be able to sort that out for you.

Pete
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AnswerID: 146827

Follow Up By: Pajman Pete (SA) - Friday, Jan 06, 2006 at 16:54

Friday, Jan 06, 2006 at 16:54
That didn't work,

try this one:

Regulator

Ebay item 5850561750 if I still haven't got it right!

Cheers

Pete
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FollowupID: 400291

Follow Up By: Lunar - Friday, Jan 06, 2006 at 17:43

Friday, Jan 06, 2006 at 17:43
Thanks mate, starting to get a bit complicated and I like kiss, I already have a PV I am happy with, I spent more on it so I could get accurate readings, but cheers for the info and good thinking.
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FollowupID: 400298

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