If the battery won't start your car, you usually refer to it as "dead," even though that's not technically correct. A battery that's merely discharged - from leaving your headlights on or from a damaged alternator -- can be recharged to its full capacity. But a battery that's at the end of its service life can't be recharged enough to restore it to a useful power level. Then it truly is dead, and must be replaced.

If the battery is discharged, not dead, you can jump-start it from another fully charged battery. About 30 minutes of driving should allow the alternator to charge your battery until you take it to a service station for a full charge. But if the alternator or another part of the electrical system in your car is damaged, they won't be able to recharge your battery. So if your battery keeps discharging, before you replace it, have your electrical system checked. What looks like a bad battery could be an electrical system problem. If you have a bad component in the electrical system, it will keep draining a new battery, and you'll be stranded again and again.
SAFE BOOSTER CABLE OPERATION
  • When jump starting a vehicle, always wear proper eye protection and never lean over battery.
  • Inspect both batteries before connecting booster cables. Do not jump start a damaged battery.
  • Be sure vent caps are tight and level.
  • Make certain that the vehicles are not touching and both ignition switches are turned to the OFF position.
  • Refer to the vehicle owners' manual for other specific information.
  1. Connect positive (+) booster cable to positive (+) terminal of discharged battery.
  2. Connect other end of positive (+) cable to positive (+) terminal of assisting battery.
  3. Connect negative (-) cable to negative (-) terminal of assisting battery.
  4. MAKE FINAL CONNECTION OF NEGATIVE (-) CABLE TO ENGINE BLOCK OF STALLED VEHICLE, AWAY FROM BATTERY.
  5. Start vehicle and remove cables in REVERSE order of connections.