Battle cred is earned and lost during battle mode. If you defeat someone with more battle cred than you, you will earn 15 battle cred. If you lose to someone with more battle cred than you, you will lose 5. If you beat someone with more battle cred than you, you will get more battle cred, and conversely, if you lose to someone with less battle cred than you, you will lose more than 5 battle cred.