My 2014 Ford Territory has intermittent voltage drop despite having a new battery

If everything is working properly, it’s less likely to be a stuck or fused relay as that would affect the operation of that circuit. In any case most relay-controlled circuits would probably be disconnected from the power source (the battery) when the car was not being used. Which, of course, brings the ignition switch into play as a suspect, on the basis that it might not be powering the car down fully when switched off.

Typically, problems like this are caused by boot lights or courtesy lights somewhere on the car staying on. In the Territory, these functions are controlled locally by micro-switches (on doors and tailgates etc) and in an overall sense by the body computer. Body computers on this generation of Ford have been known to fail, often with consequences for all sorts of functions including the central locking and possibly the courtesy lighting. Check the car on a dark night to see if there are any lights stuck on.

A security system/alarm is another great source of battery drain. Does the car have an aftermarket alarm? Even if it has just the factory security system, that would be worth checking as a cause for the battery drain. Is the car’s stereo powering down fully when you switch the ignition off? This can also be a cause of flat batteries. Again, the body computer might be the culprit.