How to Jump a Battery


Your car is old. Usually that’s a good thing – it’s what makes it a classic. When it’s not so good is when you realize that old cars break down a lot more often than their younger counterparts – six times more often to be exact. In fact, almost 40 percent of those who participated in the 2004 Hagerty Protection Network Hobby Survey have spent some quality time with their car on the side of a road somewhere. Eleven percent of their breakdowns were caused by a dead battery. Here’s what you can do if something similar happens to you.

If your parked car doesn’t want to start, you might have left the lights or radio on and subsequently drained your battery’s power. In this case, it’s wise to grab a pair of jumper cables and a good Samaritan who’s willing to let you leach off his/her battery power. First, verify voltage. If your car has a 6-volt system and the booster vehicle has a 12-volt system, abort the mission. That much voltage can fry your car’s lights, gauges and other electrical components. Next, inspect the battery. If your battery is leaking fluid or is cracked, you’re better off just replacing it. Clean the battery terminals of corrosion as well as possible, making sure to shield your eyes and skin from any battery acid, even if it’s dried. Third, park the booster vehicle as close to yours as possible, without allowing them to touch. Then place the cars in park or neutral (depending on if they’re automatic or manual), turn off the ignition, lights and radio, and unplug anything connected to the cigarette lighter or any other power outlet. Now you’re ready to connect the cables.

Keep in mind that, while jump starting a car is a relatively benign process, there is potential for an explosion caused by the ignition of hydrogen gas that forms as the battery discharges and loses fluid. This is more likely in a car that has been sitting for a long time in an environment with very little air circulation. Still, it’s best to put safety first. By making sure that you connect the cables in the correct order, you’ll reduce the chance of sparks that could ignite any built-up gas.

First connect the positive (red or orange) jumper cable clamp to the positive terminal of the dead battery. Then connect the positive jumper cable clamp to the positive terminal of the booster battery. Next connect the negative (black) clamp of the jumper cable to the negative terminal of the booster battery. Finally, connect the remaining negative jumper cable clamp to any unpainted metal far away from the dead battery, such as the alternator mounting bracket. Do not connect the cable to the negative terminal on your battery – this could lead to an explosion.

Once the cables are properly and securely connected, make sure they’re safely away from any moving parts such as fans or belts, and start the booster vehicle. Let the battery charge for at least one minute before attempting to start the dead car. Once the dead car is started, let both idle for several minutes before disconnecting the cables in reverse order of which they were connected, making sure that none of the clamps touches another until all four are disconnected.

When it’s up and running, it’s wise to drive the freshly charged car to a safe location before turning it off again (in case it will require another jump). It wouldn’t hurt to remove the battery and place it on a charger overnight – just to make sure it’s fully charged.


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