Hybrid battery charges but discharges all of a sudden, from 6 or so full charge lines to none. Can I switch off hybrid battery and run the car like a non hybrid car using 12 volt battery in the car? With check engine and IMA light on, I was getting 32 MPG on the highway from past two years even though dealer said hybrid battery need to be replaced spending about 3500. Now from past couple of weeks I am getting around 21 MPG after the battery sudden discharge often.