i could be wrong, but it sounds to me like your alternator just isn't putting enough oomph out at idle. i'd look for an replacement alternator that kicks more out at idle, or i think you can change the pulley size on it, for more current/rpm at the expense of HP.
i think a conditioner, tank circuit et al will only help if the low battery alarm is a momentary thing. if it continually complains until you rev-up, i don't think they will help.
just my two cents.