There ha been a bug with newer lights; serial numbers beginning in NAxxxxx where we have seen some firmware issues with. The battery should be fine, but the firmware reads the battery level incorrectly.
We have a fix due for release in the near future. But in the meantime, if you're using the iOS app, you can press and hold on 'forget this light' and you will be given an option to reset the light. Upon doing this, you should see the true battery level. Our apologies for the inconvenience.