You have to run the BIOS one time and set everything back the way you had it. Then SAVE IT!!!
Once that is done, then everything should be back to normal.
If that doesn't work then put back your old battery and then re-setup everything in the BIOS and then SAVE IT!!!
The batteries in today's computers will outlast the life of the computer by 10 years. These are 20 year batteries. There is a possibility that you had a bad battery, but chances are you just wanted to change it because you could.
If it is an old 486 or P1, then its time to change the battery and make sure you replace it with the same battery type and size. Then enter the BIOS change everything back the way you had it and then SAVE IT!!!