When you don't use all the energy generated by your solar panels during the day, a solar batterycan store the excess so you can use it at another time. For example, at night or on particularly cloudy days when your panels aren't generating as much energy. This means you can use even more of your renewable and free. The reason why solar batteries often won't provide your home with back-up power is due to the safety risks involved in doing so. Your solar panels and battery are connected to the main grid. During a power cut engineers will. Solar batteries with back-up power have a relay (a switch) which will automatically disconnect your electricity supply from the grid when it detects a. This depends on the size of the inverter in the battery. In a solar battery back-up system, the battery needs to hold enough power for your everyday use while keeping some energy in reserve in. This depends on the type of back-up system you have. Some lower cost batteries will automatically discharge their stored energy when a.