alternator

What keeps shredding my alternator belt? Is the alternator bad? Or is the idler pulley bad? Could it be the flywheel? Both alternator and idler pulley will spin a couple revolutions with the spin of a hand. Should they spin longer than that? Can anyone recommend a good replacement alternator?

Reading the posts on adding a second battery to my Sportster. Going with the Perko switch idea, but it appears to have two varients of the switch -- with or without the Alternator Field Disconnect. From the literature this appears to be a failsafe to protect your electrical equipment in the...