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Posts: 4
Reply with quote  #1 
Hi guys and gals. This is my first post and I'm glad to find you here. Ok to my question-s. I found some commercial grade solar panels online that are damaged and in considering picking them up. They are Q Cells Q.Plus L-G4.2 335W 72-Cell Polycrystalline solar panels. See attachment for details They are damaged but I'm sure I can salvage at least 3 of the 4 and possibly all four. I hesitate due to my lack of knowledge in wiring panels being as I currently only have two panels witch are 12v panels that I simply use each without charge controller to charge their prospective individual battery. These panels being 335w with 46.8 open voltage i'm not sure whether or not these can be used as home application and if they can how to wire sinse they are way more than 12v panels. I do understand I could wore my batteries in series to compensate the extra voltage. But the particulars I'm not sure about. If someone has knowledge of these type panels help would be greatly appreciated before I purchase. They are listed at a very good value and would go a long way in expanding my solar ability but uncertain of the purchase at this time. Thank you in advance. Jt

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Posts: 5
Reply with quote  #2 
You will need a 1600 watt + charge controller. Best results to wire in parallel.  Do not connect these to a battery directly. You will then need to understand your charge controller and how it will work with your system. 

Posts: 4
Reply with quote  #3 
Thank you for responding. Wasn't sure these commercial panels could be used for home use. If you think they will work I am going to make purchase? I can buy all four for $150 so even if I can only get two working I think it would be well worth it. Thanks again

Posts: 4
Reply with quote  #4 
Thanks for reply. I was unsure if these commercial panels could be used fir home use. But if you think they are a good value instead of buying more suitable panels then I will make purchase. These are damaged but I feel I will be able to repair three of them one is crushed. Thank again.

Posts: 4
Reply with quote  #5 
Could you give me an example of a charge controller as so i could do some research. Thanks

Posts: 116
Reply with quote  #6 


These are a couple of controllers that are often used in off grid builds. You will see a number or rating on them such as 250/100 at x volts. In most cases what that means is the controller can handle up to 250 volts dc maximum coming in to it from the panels. That includes worst case scenarios such as in the winter when your panels can actually output a higher voltage than what they are normally rated for. Your panels are rated max at about 47 volts. If the temperature in your area gets to say 30 degrees F then the panels can output up to 20% higher voltage. Say 56.4 volts. So in this case you could put 4 panels in series which keeps the maximum voltage at 4 x 56.4 = 225.6 Vdc. The current should maintain at no greater than the 9.54 Amps rating at short circuit.

The second number(100) in the charge controller rating is the maximum current it can output to charge the batteries. You would need to match the controller output voltage to the battery voltage that you want to maintain. If you want a 24 volt system then you would get maybe a 250/100 rated at 24 volts. The controller will have a range of voltages to set to know when to charge heavily(low battery) and when to charge lightly(nearly full battery) that you should be able to set. Hope this helps.


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Posts: 3,053
Reply with quote  #7 
Consider this one:
Depending on your battery voltage it may work, they have others.

Charge controllers are generally rated in AMPS (output), so the higher your battery voltage, the more watts they can handle. The "Kid" is rated at 30 amps. At 12v this is only 360 watts, but at 48v it can handle 1440w, so the higher voltage is advantageous.

You can get inverters in any common voltage, but if you MUST have 12v, you'll have to get a bigger controller or use several in parallel ($$$).

Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
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