Connecting panels

[Jason Wilkinson]

 Hi to all.   I'm thinking of buying four  24 volt panels  250 watts/7amps.  Was told  " max panels per string is 3. connect them series/parallel  the MPPT controller will do the rest".    My system is 24 volts. I;m thinking series/parallel 2 each gives me 48v/14 amps (volts too high)  or 4 in series 96v/7amps  again volts too high   or all 4 in parallel 24v/28 amps    (i need the amps)  Is it true that no matter how i connect them the MPPT will still give me the max amps into the battery ?

  Jason

[gww]

It is true that with an mppt controller the voltage will be converted to amps.  Most of the good controllers have a voltage limit.  If you exceed the voltage it could damage the controller.  Also when amps are mentioned by controllers they are refering to controllers out put amps, not imput.  You also really have no reason to go higher then two in series unless you have a really long wire run.  If you stay closer to double or less then your battery bank voltage it will convert a little more efficentlly.  4 in series will surpass most controllers voltage limit in cold weather.
gww

[Crispy]

Jason,

You didn't mention which brand / model charge controller. The greater the distance between your panels and the controller the more to your advantage it will be to keep the amps lower in order to be able to use smaller wire. It can be substantial $$$ savings.

Play around with this calculator. The Midnite Classic 150 controller should be able to handle possibly 5 panels in series at 24v 7A each so 4 in series would be no problem at all. Once you get all the numbers plugged in just play with the numbers in the parallel and series boxes to see what effect each configuration has. Hint: Even when you have 4 in series and none in parallel, you still have to put a 1 in the parallel box.  http://www.midnitesolar.com/sizingTool/index.php

gww, He's in Barbados. Not very likely to have hyper VOC issues there 

[gww]

Crispy
Good eye.
gww

[richhagen]

There is still benefit in matching the paralleled strings as closely as practical by voltage for an MPPT controller.  The controller can only adjust the voltage coming into it from all of the strings together.  As an absurd example, if you were to take six identical panels and connect three in series to the controller and the other three individually in parallel to the controller, you would reap much less power than if you were to connect two strings of three for example.  In the first example the voltage would have to drop to what the single panels were able to contribute in order for them to contribute anything, and that would be terribly inefficient for the three in series.  In the second, with two strings of three in series with those strings connected in parallel to the controller, the controller can adjust to the voltage where maximum power comes in, which for the two strings should be similar and therefore make much better use of the panels. 

[Jason Wilkinson]

   THank you guys, since i don't have a charge controller yeah i know  i know)was just thinking of getting the max amps into the battery