...and while testing things, here is something I just tried based on the code in my previous post using the ADCIN command:
Code:
' Start program

MAIN:
    ADCON1 = %00110000   ' I prefer to be sure to have FRC for the beginning at least
    VRCON  = %00010000   ' Enable the VP6 reference
    ADCIN 13, Bat_Value  ' ADCON0 = %10110100 where bits 5:2 are the 0,6V reference's channel address (1101 = 13)
    LCDOUT $FE,2,DEC5 Bat_Value
    PAUSE 1000
GOTO MAIN

END
The results are @5VDC I read 8640 and 9790 @4,2VDC (?!) but it looks to work somehow.