Recently I bought a versapak compatible Dustbuster. I left the batteries in the vacuum and for charging even during months of non use. Now the batteries are toast and can’t hold a charge for more than two minutes. I bought new Black&Decker batteries. Should I remove the Dustbuster from the vacuum after it charges? How long does it take to charge? Can I leave the Black&Decker batteries in the charger for extended periods of time? I would really appreciate your views regarding this. Thanks.