Battery issues can be a result of manufacturer error, water damage, or user error by way of frying the battery with a charger that outputs anything other than 12.6 volts, OR the unit is so old that the battery has naturally deteriorated past a point of acceptable function.
We have some troubleshooting articles that can help. However, if you've already tried diagnosing the issue yourself, please open a support ticket above so we can assist you in getting the DemerBox to us for a diagnosis and/or repair.
Here's an article on how to make sure you are charging the DemerBox properly.
If you think your DemerBox battery isn't lasting very long, please check out this article for more details.