A car engine can start with a new battery even if the alternator is bad, but it won't be able to run for long. The alternator is responsible for charging the battery and supplying power to the electrical system while the engine is running. Without a functioning alternator, the battery will eventually drain and the engine will stall.
If you are able to start your car with a new battery, it is important to have the alternator checked as soon as possible. Driving with a bad alternator can damage the battery and other electrical components.
