What should i do with the 3rd panel while i wait for the other 3?
Unless you have a long distance between the charge controller and the array, Run your strings so they are closest to 2x the battery bank voltage. If you are running a 48 volt battery bank, check to see if you will exceed the limits of your charge controller.
Next time please include;
Wire length is 8 feet for 4 panels and the other two will be 12 feet from battery bank VMP is 31 volts on all 6 panels. Thinking of adding 2 more in Aug for 8 total
Bank is 8 Trojans L16 strung at 24
At 24 Volts how many panels do you think my Xantrex could handle ?
It's an interesting question. I suspect you can put as many on as you want and the controller will handle them, reducing output to 60 amps. Most panels that could cost effectively be handled, is limited by the 60 amp maximum output, at @28 volts would be 60amps x 28volts = 1680 watts and since panels NOCT (Normal Operating Cell Temperature) value runs about 75% of the panel rating, you can add a 1/3 of that value or about 2240 watts.
8 panels for 265 watts x 8 = 2120 watt array, looks like a pretty good number.