I've got a '02 Jeep Grand Cherokee. About three weeks ago, it suddenly
failed to start -- no lights, no chimes, no meters -- this just an hour or
so after driving it without a hint of battery problem. The battery (which
came with the car) has one of those little windows in it, showing green
(which I presume to mean charged). But putting a charger on the battery
showed (on the charger's meter) that the battery was dead. I put another a
new battery in the car, the car started fine, and has run without incident
for three weeks now. The old battery I charged overnight. The charger
meter read fully charged. I unplugged the charger (still connected to the
battery) and left it for several days. I plugged the charger back in and
quickly the meter showed the battery to still be fully charged. I've done
this several times over three weeks. The old battery is clearly holding the
charge. The new battery (in the car) is clearly holding a charge.

My questions: why would a battery that continually holds a charge suddenly
go dead like that one time, but then easily continue to hold a charge when
recharged? And, why would one battery that holds a charge continue to
function well in a car when another battery that holds a charge suddenly
lost that charge in the same car? Connections were always tight and solid
(I tested).

Bottom line: is the old battery likely to flunk out again once I put it in
one of my cars? Is there a difference between holding a charge sitting on
my garage floor and holding one while hooked up to my engine (when a
different battery is maintaining its charge in the same location)?

Jim Beaver