All Voltaic batteries are designed to charge and discharge at the same time - this is called pass-through charging.
This means you can have a solar panel or some other power source recharging the Voltaic battery while another device (cell phone, tablet, laptop, etc) is taking power from the Voltaic battery.
If your device uses more power than is being generated by the solar panels, then the battery will eventually drain, but slower than it would normally.
Contact Voltaic Tech Support