2012 Focus Battery light issues

[ctwogroup]

What's going on here??
a. Whilst driving my grand daughter's Focus, the battery light occasionally comes on for approx 3 mins and then goes off and doesn't come on again.
b. When the battery light is on and I have been able to test the alternator it is charging 14 volts!!
c. When the battery light comes on and I stop the engine immediately then restart the engine, the light doesn't come on again!!
d. This only occurs occasionally as I said, we can drive the car for weeks with no occurrence of the battery light!

I have tried to follow a wiring diagram but there are so many versions out there it is difficult to find the correct one.
I have been told it could be an earth issue, a faulty battery and/or a faulty alternator(regulator)

It's becoming annoying now, so any ideas from you guys that would help me narrow this annoying glitch would be welcomed.

Many thanks