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Thanks for posting
It's not unusual for the battery to lose two bars overnight. The batteries don't give much warning when they go out, I'd recommend that before buying it you invest in a bout $100 and have a dealer do a complete "health check" of the engine control and hybrid system which would include a HV battery analysis to detect weak cells and any other areas of concern. HV batteries and major components like ac/dc inverters tend to be a little expensive as are most parts for the Prius. The batteries tend to have problems at this mileage.