Honda civic struggling to start

[rpfn140378]

Hi guys, my wife today was having some difficulties to start my civic to go to work.
The car has a new bosch battery that I fitted myself last May. Today was minus 2 degrees here where I live but for the last few days the temperature was a bit lower than that and the car was starting as usual.
I was commenting with one of my friends and he came up with one idea that I never heard about. He said to me to start the engine and disconnect the positive cable of the battery, if the engine is still running it is because the alternator is charging normally, if the engine dies it is because the alternator is going bad and I need a new alternator.
Has anyone heard anything similar or tried this?

 

[RonJ]

Don't do the test your friend suggested. It has potential to damage sensitive electrical components, such as the ECU.

You need to better describe the starting problem. Is it that the starter won't crank the engine or that the starter cranks the engine fine but the engine won't start?