Motorcycle Repair: Battery Tender vs. standard charger, trickle charge, winter storage

Question
What is a Battery Tender and how does it differ from a standard Sears or Wal-Mart auto battery charging unit?  Mine is selectable between 6 or 12 volts, but no "trickle charge" setting.  Is this important during winter storage?
(Getting ready to store my first bike for the late fall/winter season!)

Answer
A battery sends a constant current, depending on what you set it to, to the battery. If left on, after the battery is charged, for a long period it will ruin the battery.
A battery tender sends a current to the battery until its charged and then shuts itself off. As the battery drains over time it will kick back on and charge the battery. Using one will make your battery last longer if you park it for long periods of time
Good luck and happy riding
Mike