grid tie panels off grid!!!!

[davechezz]

Hi all

posted earlier in week about 4 panels i have bought..and found out that they are not 12v or 24v but grid tie panels of approx 20v!!!! Can I wire these in to 2 sets of 2 in series to charge a bank of 24v batteries?

Regards
dave

[organic farmer]

As I understand, you have four photovoltaic panels, that each produce 20vdc.

There is no such thing as a 'grid-tie' panel.

If you wired all four of these panels in series you should be able to produce 80vdc.
Or you could set them up in two strings of two in series and produce 40vdc.
.

[littleharbor]

I believe I was the one who answered your question and explained what is required. If the explanation wasn't clear enough I would have been happy to clarify my answer.

60 cell grid tie panels are considered 20 volt "nominal" when compared to 36 cell, 12 volt and 72 cell, 24 volt panels. Their voltage isn't high enough to properly charge a 24 volt bank of batteries and is too high to efficiently charge a 12 volt bank with a conventional PWM charge controller. When used in an off grid scenario you would need an MPPT charge controller to step down the voltage to match your batteries and series wire panels when necessary to raise your voltage higher than your battery bank needs leaving the controller to do it's magic.

A quick google search shows a Vmp of 29.6 volts and a Voc of 36.6 volts.

If you want to charge a 12 volt battery bank a single modulehas sufficient voltage to work with an MPPT controller. If you are going 24 volt then you would need to series wire at least 2 panels and use an MPPT controller.

....or take Organic Farmers answer because it sounds like he knows what he is talking about..

[davechezz]

Thanks for the answer and the one the other day i did reply ( think it was to you) regarding series wiring! Im afraid i am very green with this and need as much advice as i can get in easy to learn steps!!!

kindest regards Dave

[peakbagger]

How you deal with the panels depend on what you want to do with them. Be aware if you put a voltmeter across a "12 volt panel" that is could read 17.5 volts if there is load across the terminals . 20 volts sound suspicious, its low for a grid tie panel. It would helpful for you to post the data that is usually on the back of the panel. Once we know the panel characteristics and the proposed use, possibly charging 12 volt batterys? then its lot easier to make recommendations.

Assuming that they are higher voltage panels, you can buy MPPT charge controllers that will convert the higher voltage form the panel to the voltage you want to the output voltage. Alternatively you can buy a PWM controller and just get a bit less out of the panel. MPPT controllers are more expensive than PWM so its a trade off.

[davechezz]

Hi thanks for the reply.
i posted in the section solar living the other day and that post has all the specs for the panels and other hardware i have. If you could find time to read it and then let me know what i could do with them i would be most grateful for any advice you may have

kindest regards Dave

[inetdog]

As long as you use an MPPT Charge Controller instead of a PWM CC you can use a string input voltage that is much higher than the battery voltage.
If you are starting out with a PWM CC and do not want to replace it, then you will have to accept losing out on half or more of the power output of your panels.

[Sunking]

Hi all

posted earlier in week about 4 panels i have bought..and found out that they are not 12v or 24v but grid tie panels of approx 20v!!!! Can I wire these in to 2 sets of 2 in series to charge a bank of 24v batteries?

Yes as long as you use a MPPT Controler.