Upsizing Solar PV system

Submitted: Friday, Oct 24, 2014 at 01:58
ThreadID: 109911 Views:1263 Replies:5 FollowUps:2
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We have a dual battery system in our Landcruiser Troopy camper, powered by Solar PV. We originally bought an 80W (4x20W) mono crystalline system, but this was not enough for our fridge and computer charging when we were in Tassie last year.

We expanded this with a 40W semi-flexible panel (bought over the internet), and this gave us enough charge most of the time, depending on clouds and shade. After almost 1 year, the 40W panel died, and there was no response to our emails about this from LenSun HK.

So now, we need to upsize the system once again. I have seen articles and comments that additional panels need to be 'compatible'. I am also thinking about where to store the extra panel/s...

My questions:
- What is 'compatible'? My current mono crystalline panels each output ~20V and 1A = 20W. Should any new panels also output ~20V? Should they be mono crystalline? Can I incorporate the new fully-flexible panels onto the same charge controller?
- What are your experiences with the semi-flexible panels? They take up less space, but how reliable are they?
- Where is a good place to buy 20W or 40W panels?

Happy travelling
Rob
Rob and Rita - semi-retired telecommuting from anywhere!

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Reply By: DmaxQld - Friday, Oct 24, 2014 at 09:35

Friday, Oct 24, 2014 at 09:35
Do you also charge your aux battery from the Troopie's alternator?
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Follow Up By: Member - DrRob - Friday, Oct 24, 2014 at 12:44

Friday, Oct 24, 2014 at 12:44
Yes I do. I have a mechanical Cole-Hersee switch which lets me charge (and use) batteries 1, 2 or both.

I know it's preferable to get a modern, automatic switch/ charger, but I can't justify the cost yet.
Why do you ask?
Rob
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Reply By: oldtrack123 - Friday, Oct 24, 2014 at 11:00

Friday, Oct 24, 2014 at 11:00
HI Rob
20V is an unusual voltage for solar panels
Perhaps more details??
Paralleled panels can be different wattage, but should have the same voltage at their peak power rating..
Depending on makers that voltage should be 17<18V @ PPP
And 21<22V open circuit
Also best to keep to same type


PeterQ
AnswerID: 540786

Follow Up By: Member - DrRob - Friday, Oct 24, 2014 at 13:38

Friday, Oct 24, 2014 at 13:38
The 20V is what I measured from the panels, so this would be the open circuit voltage. The panel specs are 17.5V and max current 1.14A.

The brand is DE-Tech.

So what you're saying, (and the Bantam below) is that I should stick with the same brand, and, if not, go for something with the same output voltage.

And yes. I've used thick cabling and the charge controller/ regulator is near the batteries.

Thanks for the advice.

Rob
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Reply By: MEMBER - Darian, SA - Friday, Oct 24, 2014 at 11:51

Friday, Oct 24, 2014 at 11:51
Just on buying the panels - many users reporting here and elsewhere buy their panels via a number of suppliers on Ebay.... overall, this seems to be a good idea because those suppliers seem to have proven to be reliable and provide good value for $. They include Ozplaza, Bit Deals and Low Energy Developments (I have dealt with the latter, mainly because I could ring them and discuss aspects of the product !.... but I'm sure there are other good dealers). From what I can see, such providers represent the lowest prices around. I bought a 120W folding kit - I paid about $100 more than the cheapest, but it came with a better regulator than the cheapies, had several optional connection cables and a decent quality carry bag - still doing a good job after several years). The foldables cost a bit more but pack smaller of course, but that may not matter in your application; the sellers include the dimensions and the weight for each panel in their listings. I'll leave comment on compatibility and connections to the techno's here.
AnswerID: 540791

Reply By: The Bantam - Friday, Oct 24, 2014 at 12:12

Friday, Oct 24, 2014 at 12:12
Consider that the solar technology is still moving forward at a fair pace.

If you buy now and you buy current technology product, it may pack more power in the same space and may be more efficient.

SO

you may be better off doing your homework and buying alll new pannels and selling the ones you have.

This way you know that you have pannels all the same and are compatable and best efficiency.

On the matter of the 20 volt pannel.

There was an ebay seller that was actually selling 24 volt pannels( there where heaps arround when the subsidy dropped) as 12 volt pannels and either knobling them or recomending a strapping arrangement that was less that workman like.....this pretty well resulted in a section of the pannel doing nothing and the voltage still bing not quite right for a 12 volt system.

The other thing is cabling....significant improvements in efficiency can be had by cabling your system in heavy enough cable and putting the regulator close to the batteries..

cheers
AnswerID: 540793

Reply By: MARIC - Monday, Oct 27, 2014 at 19:19

Monday, Oct 27, 2014 at 19:19
Have a read of Caravan and Motorhome issue number 208.
They have a very comprehensive article on Solar Panels and regulators.
Worthwhile reading.
It is only when you see mosquito land on your testicles that you find another way to solve problems without violence

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