Dell Inspiron 6400 Battery not charging

I've had my laptop for almost 3 years. As time went on, when not plugged in, the battery lasted for shorter and shorter periods of time. A few months ago I was using it and had to unplug it, but didn't shut it down (I was going to plug it in across the room, which was a large room.) Before I got to the other side and plugged it in, it died completely. The orange battery light began blinking when I did plug it in.

So I resolved to the fact that the battery was dead and I could only ever use the computer when it was plugged in. I didn't want to spend a few hundred on a new one.

But recently I was shopping on Amazon and realized I could get a new battery for around $50. So I did. It arrived today. I placed the new battery in and the battery light began blinking - alternating green then orange. The power meeter was at 33% when I put it in and it hasn't changed after 8 hours.

Is this not a good battery or should I get a new charger, and is there a way for me to know for sure?

Thanks!
Robin in Hawaii