battery charge fault....

[sym]

hi, ive got the battery charge fault message on the display of my car, i changed the alternator today due to the old one having a squeeky bearing, 1st alternator was put in & i got the message up & the alternator was making a hell of a racket so i took it back to the shop but they were shut, so i got another from ecp, it sounds fine but im still getting the message up along with the beeping, ive also put another battery on aswell, whats the chances of having 2 iffy units from 2 different suppliers, does it sound like it could be a bad earth?il get a multi meter & check the voltage but im limited when it comes to electrics, any pointers would be appreciated, thanks, lee