[cheryl j (OP)]

It will power the laptop if the battery is dead, and my battery will charge with my daughter's adapter. Why won't my adapter charge my battery?

[RD]

It will power the laptop if the battery is dead, and my battery will charge with my daughter's adapter. Why won't my adapter charge my battery?

You computer's battery management settings are worth a look ...

... For example, your battery settings may cause trouble if you have set the computer to shut down when the battery level drops too low and set the low battery level at too high a percentage ... If these settings have been changed, it's easy to suspect a power malfunction even though there's no physical problem with the battery or charging cable. The easiest way to make sure that your settings aren't causing problems is to restore the power profile to default settings.  ...

, see #7 ... http://www.pcmag.com/article2/0%2c2817%2c2404105%2c00.asp

[syhprum]

If your battery will charge with another charger there can be little wrong with the settings of you computer.
Byte the bullet and buy a new charger from a store that is willing to test on your computer.

[cheryl j (OP)]

Yeah, I think it is the adapter itself. I hate to invest in a new one since the lap top itself is fairly old. It just seemed strange that it would power the laptop but not charge the battery. You'd think it would be all or nothing.

[syhprum]

PSU devices often start out with a bridge type rectifier feeding into a large capacitor which then feeds into the chopper type electronics, bridge rectifiers have a nasty habit of partially failing and putting out a reduced voltage with a greater ripple.
The chopper electronics "bravely" try to cope with this but the end result is that the PSU outputs less than its rated output voltage that may well be enough to get the computer going but not enough to charge the battery.
It is quite difficult to measure the actual voltage the PSU is putting out without dismantling but if you do you will probably find it is about 10-15% low with some mains frequency ripple on it.