Walking out to your car in the morning to a dead battery is a lousy way to begin the day. If your vehicle was running fine when you parked it, your battery has probably dropped below the charge level necessary to start the engine. Learning how to jump a car battery isn’t difficult, but it can definitely be intimidating for first timers. Here are some of the reasons why your battery might have died and some tips for jumping your battery that will help you get you back on the road in no time.
Why Did My Battery Die?
The most common cause of a dead battery is leaving your lights on all night long, but that’s not necessarily the only way to drain your battery. Other culprits can include an interior light that doesn’t shut off due to a faulty door latch or trunk switch, or even a poorly installed stereo system, subwoofer or car alarm that may be leeching power through a short circuit. Some interior 12v outlets and USB ports stay powered even when the vehicle is shut off, so a phone charger left in place or dash cam could be the culprit. The problem could also be with the vehicle charging system itself such as a bad alternator or voltage regulator. There could also be a simple loose wire. If you find your battery is constantly dying on you, it’s worth heading to your local NAPA AutoCare expert to diagnose the problem. A battery can only be completely discharged so many times until it is out for the count, so it is worth finding out the root cause of the dead battery problem.
There are two basic tools used to jump a car battery. The first are standard jumper cables, which are intended to connect your car’s electrical system directly to that of another vehicle nearby, allowing you to use its juice to get your engine going. Jumper cables have been around for decades. You’ll need to choose the right length of cable; standard units force you to park face-to-face. That’s not always possible on a busy highway, however, where it may be safer to park nose-to-tail and use a set of extended cables. Thicker cables, noted by their lower gauge size, will also transmit electricity more efficiently, which makes for easier jump-starting. Solid copper clamps always beat copper-plated clamps, as the latter design can wear off over time and significantly reduce your ability to jump a car battery. There are even “smart” jumper cables that can warn you if they are connected wrong.
Another option is a portable power pack, which is a self-contained battery you can keep charged in your trunk or garage. The pack can be attached to your car’s battery and save you from having to wait for a rescue. There are traditional jump boxes that contain a small sealed lead acid battery capable of starting most vehicles. Newer jump starters lightweight Lithium Ion batteries for rescue power. There are even batteryless jump starters that use ultracapacitors to build up a starting charge. Most of these portable power boxes also double a power bank for charging USB devices, so they are handy for camping and tailgating.
Making the Jumper Connection
Regardless of whether you use jumper cables or an emergency power pack, learning how to jump a car battery requires you to understand how to make the right connection with your vehicle’s electrical system. Always check your vehicle’s owner’s manual for any special instructions for hooking up jumper cables. You also need to locate your battery as not every manufacture placed it under the hood anymore. Some vehicles may have special remote connections points or the battery may be located in an odd place like under the rear seat or in the trunk. Your owner’s manual will give you the exact location of your battery if there is every any doubt.
Although you are likely familiar with the concept of connecting the positive terminals and negative terminals together using jumper cables, it’s a good idea to clamp to the chassis of the car being jumped instead of the dead battery’s negative pole. This provides you with a stronger ground — the battery itself has to ground out through the chassis, so you are cutting out the middleman — and ensures that any sparks that might fly are located far away from the battery, which could be venting flammable gases. Connect the jumper cables to the dead vehicle first, followed by the helper vehicle (which should not be running yet). When the vehicles are connected start the helper vehicle and let it run for a few minutes to give the dead battery a bit of a charge. After a few minutes you can try and start the dead vehicle. If it doesn’t start after a few rotations or is slow to turn over, stop and let the battery continue to charge from the running vehicle. You may have be patient and wait 10-15 minutes for a good charge depending on the vehicle’s starting needs.
If you are using a portable battery pack, you’ll follow the same steps: positive cable to positive terminal, negative cable to negative terminal or ground pole/chassis. Lastly, make sure that the pack is on and ready when you crank the ignition on your vehicle.
Once the dead vehicle finally starts remove the jumper cables or battery pack in reverse connection order. If you used a portable battery pack make sure to switch the pack off. Do not shut off the now revived vehicle until it has been driven for at least 20 minutes. Driving is preferred to simply idling in place as it brings the engine RPM up and past the minimum alternator speed required by some vehicles to charge. Lastly if never hurts to swing by your local NAPA Auto Parts store or NAPA AutoCare to have your battery tested.
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Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time. I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.