First did you follow this guide to the letter? [guide|10759] If not what else did you do?
I’m suspecting your PRAM settings got messed up as you didn’t turn off the system before pulling the battery connection.
Lets give this ia try [https://support.apple.com/en-us/HT204063|Reset NVRAM or PRAM on your Mac]
If that fails you’ll need to go to your network settings Preferences > Network
Delete the current WiFi entry and create a fresh one. You’ll need your to know your AP’s network name and its WPA password.