Chosen Solution
After I replaced the battery on my iPhone 3GS, the phone will not hold charge and can only work if you leave it plugged in. Essentially this bypasses the battery. The phone worked well for 1 day after the battery was replaced. Now it dies after you unplug the adapter.
angeleavila, there are lots of problems with the batteries. Check with the vendor where you bought the battery from. you could ask for an exchange. the other thing to do, is to check the numbers for compatibility. Also, check by reinstalling your old battery, that way you can be sure that it is the new battery that is causing this problem. Hope this helps, good luck.