Since the battery is the heart of a car's electrical system, a dead battery will bring all systems to a stop. You won't be able to start the engine nor will the headlights, radio or interior lights work. The most obvious symptom of a dead battery is when the car won't start. After parking for a while, the car just makes a labored "rrr rrr" sound or even worse, a click with nothing happening. The battery may die if something electrical was left on while the car was parked, either headlights or something less obvious.
1. Low Charge
If there is a low charge, the horn may sound weak, the headlights may be less bright than usual, and some things may work while others don't. If the battery is completely dead, the vehicle is going nowhere.
Jumping a battery from another car or portable battery will only work if the battery was dead. If jumping works, a dead battery was the problem.
The smell of acid or burning from a battery show that it is dead or may need to be replaced.
A battery can be dead because the alternator has not been recharging it. In this case, jumping the battery won't last long because the charge will drain again quickly. The alternator needs to be replaced.