TW> All of them I know about use sealed Lead Acid Batteries.   
   TW> They are "Float" type Batteries and they do not tolerate deep   
   TW> discharges very well so if you run them all the way down too many times   
   TW> they need to be replaced.   
      
   True.  I have an extra UPS that I'm not using at the moment, but I leave it   
   plugged in and charged all the time.     
      
   If you leave them off for long periods of time, they will end up not working   
   anymore.  We have had "spare" UPS batteries sitting in our computer room at   
   work sometimes for up to 2 years.  When you go to use them, they almost never   
   work after sitting that long with no charge.   
      
   - Mark   
      
   --- WWIVToss v.1.51    
    * Origin:  http://www.weather-station.org * Bel Air, MD -USA (1:261/1304.0)