alternator problem?

[Stewart1000]

im having a hard time diagnosing my mates car problem, its a VN Lexcen s2. it has a new battery in it that we put in a week or 2 ago. it gets charged for a few hours then it starts and runs fine and you turn it off and try and start it again 5 seconds later and it doesnt work. we usually end up jump starting it from his sisters car, and even then it has a hard time starting, it seems that if she revs her car our car will start easier.
so i was guessing it would be the alternator on the way out, but that wouldn't explain why its still hard to jump start her, even after she has been running.
next time i'm going to bring my multimeter and check the battery but its a good battery im pretty sure.
anyone got any ideas on what to look for or anythign at all.
i know it should be charging around 14.5v mark so ill check that but are there any ways to check the alternator?

 

[Mark]

yeah start the car and run the multimeter across the battery.. batteries are 12v so when the car isnt on u should get a reading of around that.. turn the car on and the reading should just up to around the 14.5 mark.. if it doesnt then u know the alternator isnt charging properly

 

[Stewart1000]

how long does it take to get to the 14.5 mark and then back down to 12 when you shut her down?
i'm going to try and get it diagnosed tomorrow, ill let you know how it all goes. we are also going to try and remove the rear muffler and ill weld a pipe in place for some cheap thrills lol

 

[Mark]

it should be more or less instant