Is battery bad if you jump start?

It depends on the circumstances and how the jump start is performed. Jumping a car with a dead battery can be done safely without damaging the battery if it is done correctly and using proper equipment. However, if the jump start is done incorrectly, such as connecting the jumper cables in reverse or leaving them connected for an extended period, it can damage the battery or other electrical components in the vehicle. It is always recommended to follow the manufacturer's guidelines and use proper safety precautions when performing a jump start. If done properly, a jump start should not harm a healthy battery.