There are several possible causes for this problem.
1. Does your smoke detector have a pause button?
If so, this button may have been pushed by mistake. This means that the alarm will beep once every minute for the next (max.) 15 minutes while it is in pause mode. Wait a moment and see if the detector continues to beep.
2. Are you sure it's the smoke detector?
Other devices produce similar beeping sounds or warning signals.
3. Even "new" batteries are not always really new
When batteries are stored, especially in cold areas, they lose their voltage faster. Always check the expiration date on the package when you buy new batteries. The one included with your detector is also subject to this. An included battery may not last as long as expected; this is inherent in included batteries. In that case, replace the battery and see if the problem persists