Glad it worked well for you to up the voltage by wiring the 4 panels in series/parallel. You could have accomplished the same thing by upping the wire gauge to the controller. Once the voltage drop gets up to 2 V or so, the controller can't put out enough voltage (needs at least 14.5) to fully charge the batteries. Wiring the panels in series cuts the voltage drop in half with the existing wiring.

David