Yeah, the battery doesn't last forever. It is basically a battery back up like you may have for your computer. You plug in the back up to your main power supply, then the pump into the backup. They will usually last a few days, because the sump doesn't draw that much electricity. Hopefully that is long enough to get your power back.
Then there is the manual backup system, dunking water pitchers into the catch and pouring them down the laundry sink.
The water pressure backup is probably the best bet if you can afford it.
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