bq 2084 dell d620 laptop battery not charging at all or charging to a certain extent

hi i have problem with dell d620 batterys having bq2084 ic in it. these batteries are not charging at all or charging upto certain extent say 60% 80% 90%.while discharging some of these batteries drops to zero from 50% 35% 30%.  shuts down laptop. can u have any suggestion in this regard

  thanks