N5445 Laptop Battery/Charging Question

Hey. I have a N5445 HP Pavilion laptop that I probably bought around January 2002. Still works fairly well, except that the battery I had in it refused to charge, so I always had to have the thing plugged in, because the battery always showed 0% and wouldn't turn on unless plugged in.

I recently purchased a new battery for it. It came yesterday - I plugged the new battery in and the thing turned on without being plugged in. The battery indicator showed 48% charge. I plugged it in to the outlet to charge. My charge light came on and my quick menu battery icon told me that the battery was charging. However, the thing never went above 48%.

I've heard things about new batteries not wanted to charge, etc., etc., but I'm beginning to think something's wrong here. Is it a problem with the battery, my AC adaptor/battery charger (whatever you call those things), or is it somehow a problem with my PC or something?

Any help would be appreciated.
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