It is highly recommended that the charge controller be within one meter (approximately 3.25ft) of the battery bank and in the same room or enclosure. Be sure all rooms and enclosures are well ventilated. Lead acid batteries produce flammable hydrogen gas.
Significant voltage drops occur not only with excessive distance but with improper wire size. Check the back page of the Phocos catalog to view a quick guide for wire sizing.
Measure the voltage at the controller, and measure the voltage at the battery terminals. If there is a 0.5V difference or more, reduce the wiring distance or decrease the wire gauge.