The Additional / Replacement WV 5 Battery is the perfect edition to provide even longer continuous cleaning, combining both batteries will allow up to 70 minutes of perfect streak-free results. Simply unclick the battery from your WV 5 and click the second battery back into place. The additional battery can also be used in conjunction with the WV 5 charging station, allowing you to store and charge both your Window Vac and the spare at the same time.