Reviving a dead battery. If a car won’t start because of a weak battery, it can be started by connecting jumper (booster) cables to a car that will run. Both cars must have the same type of battery, which generally is a 12-volt negative-ground, identifiable by the terminal with a minus sign or NEG being connected to body metal and usually also to the engine.
Bring the live car close to the dead one, but not touching it. Set the parking brakes; put both transmissions in Park or Neutral. Turn off lights, electrical accessories, and the ignition keys on both cars. Remove vent caps (if present) from both batteries, then cover the holes with clean rags.
Connect one jumper cable from the positive post or terminal (marked with a plus sign or POS) of the dead car to the positive post or terminal of the live car.
Because the bolts on a side-terminal battery have very small heads, the clamps may not make good contact. If they are available, install battery charging adapters; connect the clamps to them.
Connect the second cable to the negative post or terminal of the live car and to an unpainted bolt on the engine, away from the battery, of the dead one. Both cables must be clear of fans, belts, and pulleys.
Start the live car, then the dead car. When both are running, disconnect the cables in the reverse order, starting with the cable clamped at the dead car’s engine.
To recharge the dead battery enough to restart the car, drive the car at least’/z hour before stopping. Have the battery fully recharged promptly.