Yes, battery backup sump pumps are available, important, and require some knowledge of check valves to correctly and effectively install. They are powered by a 12 volt, deep cycle, car-type battery mounted in a plastic case. The battery is powered by a battery charger with electronic controls & sensors so that the sump pump runs off the battery and the charger keeps the battery charged. During a power outage the sump pump continues to operate as long as the deep-cell battery provides power to the pump. In normal conditions this is about two to four days depending on the frequency of pump cycle. Automatic backup generators offer longer protection for prolonged power outages.
Sump pumps are the active, pumping part of getting the water out of your basement drain tile system when wet weathers cause the basement to “leak”. Successful sump pump operation is most critical during bad weather such as heavy rain storms with high winds, so the backup option offers good, short term protection during inclement weather. It is a great idea to install a battery backup sump pump system if you have a finished lower level or walk-out basement. The battery backup is insurance that the sump pump continues to operate even if the electric power is lost. This better protects the value of your finished space. Redundant sump pumps are better professionally installed to get the check valves effectively piped. The GFCI or ground fault electric outlet that powers these sump pumps is also better installed by an experienced electrician for safety reasons.
My company, Mosby Building Arts, consults on the design and installation of redundant sump pump systems for basements prone to water intrusion. It is also a good way to keep a good, operating sump pump and then add a second battery backup sump pump to the already effective system. The standard sump stays installed in the bottom of the sump pit with a backflow check valve installed in the exhaust pipe to the exterior of the house. The second battery sump pump switch gets installed higher in the sump pit so it starts operating if or when the first pump gets overwhelmed or does not operate. Backflow check valves must be correctly installed so the pumps push the water to the exterior of the house and not simply blow the water back through the other pump into the sump pit. Some extreme situations where power loss occurs may suggest a backup power generator to keep pumps running when electric is out.
In summary of this type installation, most daily operations of the sump pump continues to be done by your existing sump pump and the battery unit is mounted to run only when needed. It is wise to test the operation of both pumps regularly, usually monthly, to assure they operate correctly and effectively.