battery is not chargin and is plugged in

here is how to fix it

1.  Turn off the notebook.
2.  Unplug the A/C cord
3.  Disconnect the battery.
4.  Hold down the power button on the laptop for 8 seconds.
5.  Reconnect the battery
6.  Plug in the cord.
7.  Everything should work, Repeat as needed.  (worked on my wife's HP laptop)

dell laptop batteries

i have 4 dell laptops in my house and 3 of them have batteries that are smoked.  I am a software engineer and i know you don't keep the laptop plugged in all the time because there batteries have memories etc.  The weird thing is that with these laptops it wasn't like slowly they were losing life, it was like all of the sudden my battery died and then i would plug it in and it would be fully charged, then unplug it and it would give me the low battery warning.  Of course hibernate if I didn't plug it in fast enough. 

So my questions are:

1. Why is this happening so quickly?  Why isn't it a slow progression of battery life loss?
2. Is this really a battery issue or the charging mechanism in the laptop?  I have read something about the mechanism to charge the battery could get shorted out.