Im a total novice when it comes to using a multimeter so which setting do i use? Sorry
Set the meter to 20 DCV.
…
Tester
Positive on the terminal and neg on the cable?
Bounced around for a couple minutes then settles on o.oo
That was reading from post to cable
Tested from post to cable 0.00
If the cable is disconnected from the battery, reconnect it.
With the meter, place one lead on the positive post and one on the negative.
The reading should be about 12.5 volts.
Start the engine with everything turned off.
With leads back on the battery posts, the reading should be 13.2-14.5 volts,
If not, place the red lead of the meter on the large cable connection sticking up from the back of the alternator, and the black lead on the alternator body.
The reading should be 13.2-14.5 volts.
Report back the results.
Tester
Battery 13.1 alternator 13.1
Could it be the mega fuse?
That link illustrates nothing. The article states “within 75 minutes”. A few minutes is within 75. I guess I’m done spending time reviewing your links. And I so thought we could get along… 
That test needs to be done at 2000 RPM, not idle.
HOW TO TEST ALTERNATOR CHARGING VOLTAGE
Most alternators that are charging properly should produce a voltage of about 13.8 to 14.2 volts at idle with the lights and accessories off. Always refer to the vehicle manufacturer’s specifications. Many Asian vehicles, for example, have higher charging voltages of around 15 volts.
When the engine is first started, the charging voltage should rise quickly to about two volts above base battery voltage, then taper off, leveling out at the specified voltage.
The exact charging voltage will vary according to the battery’s state of charge, the load on the vehicle’s electrical system, and temperature. The lower the temperature the higher the charging voltage, and the higher the temperature the lower the charging voltage. The “normal” charging voltage on a typical application might be 13.9 to 15.1 volts at 77 degrees F. But at 20 degrees F. below zero, the charging voltage might jump as high as 14.9 to 15.8 volts for a short period of time. On a hot engine on a hot day, the normal charging voltage might drop to 13.5 to 14.3 volts
KEY-OFF CAR BATTERY DRAIN
If your car battery is less than six years old and tests okay, and the charging system is working normally, your battery may be running down because of a key-off current drain (also called “parasitic battery drain”).
When you turn the ignition off, switch the lights off and remove the key from the ignition switch (or the smart key fob from the vehicle), the electrical load on the battery should drop to almost nothing. On older cars that do not have computers or other onboard electronic modules, the key-off load on the battery is typically only a few milliamps (if it has a clock or a digital radio), or it may drop to zero (no load at all). However, on late model vehicles with computers and numerous electronic modules, the key-off drain on the battery can range from 20 to 50 milliamps, and as much as 300 to 400 milliamps on some applications. On some Fords, the electrical system will continue to pull as much as 850 milliamps (almost 1 amp) for up to 20 minutes or more after the ignition has been turned off.
The key-off current drain is used by the modules to keep their memories alive. The chips that store certain settings and learned information are called the “Keep Alive Memory” (KAM).
Many modules have internal timers that either turn off the module to put it into a “sleep mode,” or power down the module to a “standby mode” to reduce the parasitic power drain on the battery after a predetermined length of time when the key is turned off. Some of these modules power down in steps and time out at different rates. It may take up to a half hour before all of these modules reduce their current drain on the battery to minimum levels.
Tester
The alternator is defective.
Tester
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