Enthralling question on laptop battery

[clayton_e]

A friend of mine has an older mac laptop with a battery problem. Sometimes after charging the battery will suddenly decharge in the charger, requiring an hour or so to recharge it again. It charges off one of those old battery chargers that plugged into the wall instead of charging in the laptop.

Any idea why this happens? Any way to counter it?

[Q.E.D]

Is it the type of charger with a “Condition” button? These are for the older NiCd cells, and worked on the (wrong) theory that preventing NiCd memory required occassional deep-cycling of the battery. Perhaps there is an intermittent short in this switch or the circuit it is connected to.