You left the lights on in the car while you were hiking, but the good news is you have a set of jumper cables. The bad news is, your car is the only one parked at the trail-head that day so there's no other car to attach the cables to. A jumper pack can bypass the middleman. A handy device that almost pays for itself the very first time you need to use it.
Release the hood latch and lift the hood. Place the hood prop in designated hole on the underside of the hood to hold it up. The hood prop is either on the left or right side of the fender rail, or sometimes along the front rail, and in rare cases on certain vehicles, it is tucked on the underside of the hood and there will be a designated hole on one of the rails for it. Some hoods have hydraulic props that will hold the hood open and no hood props will be required.
Locate the battery. Some car batteries are not in the motor cavity. In these cases you're going to be looking for a red plastic cylindrical cap with a large + sign on it. This is a jump post for the battery. These jump posts can be in a variety of locations depending on the make and model of your vehicle, but most manufacturers place them in conspicuous places for occasions such as this. If all else fails, refer to your owner manual.
Remove the plastic jump post caps by lifting them off by hand. You may also see a similar looking black cap with a - insignia on it for the negative jump post. If not, you can use the frame of the car. If the battery is in the motor cavity, you can attach the jump pack directly to it.
Ensure the jump pack power switch is in the off position. Attach the red positive alligator clip of the jump pack to the red positive battery terminal or jump post. Attach the black negative alligator clip to a non moving metal part of the car away from the battery, but within reach of the battery jump pack. A part of the frame would be okay, but do not attach to the painted fender. If you have a jump post option for the negative terminal, you can attach the black negative clamp to that.
Locate the power button on the jump pack and turn your head away from the jump pack and battery when you turn it on. This is a safety precaution as batteries have hydrogen gas and lead acid inside them. The hydrogen gas is highly flammable and can explode in certain circumstances. By connecting the black negative clamp to a metal ground and not directly to the battery, you have diminished this risk.
Check to make sure the jump pack itself and the cables are not going to interfere with moving engine parts. Go to the car and turn the ignition on and try to start. If the vehicle starts, go directly to the jump pack and turn the power switch to off. Disconnect the negative clamp first and then the positive. If the vehicle does not start, you'll need to shut the power switch of the jump pack off and try to reconnect following the same procedures. A lot of battery corrosion can prohibit a good connection from the jump pack to the battery. Digging the alligator clip into the soft lead compound of the positive terminal with the power switch of the jump pack off might be a way to get a cleaner connection in a hurry. Allow the jump pack to cool down for a couple of minutes in between non-successful start-ups.
