what can cause a complete electrical failure 2005 impala? The battery is good.

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I disconnected the positive battery cable to do some mechanical repairs. When I reconnected the battery, it would not crank; the instrument panel was dead; no turn signal, but emergency flashers and brake lights worked and a chiming sound was heard. I left the battery connected overnight; the next morning the electrical system was completely out as if system wide failure. The car battery is 12.64 volts at present, also tried jumpstart with 12.78 volt booster. The electrical system remained dead.