If you have a Standard Solar Fountain which only works when in direct sun and you would like it to run more consistently regardless of changes in weather, passing clouds, or not having direct sun on it all day, you can't add a battery to your original solar panel but you can order an IntelliSolar kit (which comes with a solar panel, battery pack, and pump) from our parts dept. This will allow you to turn it on and run it during the day, or turn it off and charge it up during the day. After it's charged you can turn it on at any time such as in the evening and the battery will run the pump. Here is a link to our various kits:
https://smartlivinghg.com/collections/solar-kits
The other option is using an AC adapter to run your Cascade Fountain or Tabletop Fountain on electricity. This is for use with fountains where the plug is out of the water, not for birdbaths where the plug is under water. Here is a link to the AC:
https://smartlivinghg.com/products/a6v-ac-usa