On Wed, 09 Jul 2008 06:47:07 -0700, Evan Platt wrote:

Any batteries, short of sealed lead acid, will start to hold less of a
charge over time. How old are the phones? The newer the technology,
the better they'll be at holding a charge, but still after a year or
so, it may be time to buy new batteries.

No phone weighing less than 15 pounds uses a lead acid battery. About the
last phone to use a lead acid battery were bagphones of the early 80's.

Cordless phones used to use NiCads but now use NIMH batteries or Lithium Ion.

The usuall failure occurs as a result of running the battery after one of the
individual cells has completely discharged. The other cells will force
current through the discharged cell therby charging it in reverse and shorting
it out.