Will I harm my new car by disconecting the negative terminal for four months while Iam away???
Maybe.
I would just pick up a trickle charger/battery maintainer. They aren’t that expensive and will keep the battery all charged up and ready to go.
I know nothing about your Prius, but my car and motorcycle say that if you will not be starting the vehicle for more than 21 days, you should disconnect the negative battery terminal, but most winters I just put the cycle on a trickle charger.
I don’t see why it would harm it.
With a Prius, I think we’re guessing unless someone who owns one knows for sure. Call the service department at your dealership.
What battery are you planning on disconnecting? (there are two). Disconnecting the 12V engine starting battery should not hurt anything…The high-voltage hybrid battery should be okay for at least 6 months especially in cold temperatures…
Disconnecting the 12V battery may cause the loss of some computer memory, so it may not run too smooth until it has had some time to adjust. It also may cause some problems with any anti-thierf features.
I have no idea about the motive battery.
Do read the owner’s manual.