How do I make sure my finished basement stays dry?

I have a sump pump with a battery backup. However during one overnight period recently, the sump pump died, the battery backup worked for a few hours and then it died, and by the following day the basement was flooded. The battery backup was beeping but we didn't hear it upstairs. Short of digging a second well for another sump pump, what can I do to really minimize the chance this happens again?