Jumping a Car

Just when your day couldn’t be worse, you find your car dead. Turning the key gives you the dreaded clicking, or even worse, no results. A light has been left on, leaving you stranded. What now?

Jumper Cables

The first and most frequent solution is jumper cables. Refer to your owner’s manual first for how to jumpstart your car as sometimes they have a specific way or location to jump the car, such as some Mercedes vehicles having specific jumpstart lugs in the hood, even though the battery is somewhere else. The general process is as follows: inspect your battery for damage, leaks, corrosion or other issues. If you see your battery is bulging, this also indicates a failed battery. Do not attempt to jumpstart a car with a damaged battery, as they contain lead, acid, and sometimes hydrogen gas, and can explode. After inspection, you can connect your dead car to the donor car. Ensure your cables can reach both batteries without touching any moving parts. Avoid touching any connectors to anything not described, as this can create a short and start a fire. First connect a red cable to the positive (+) or red connector of the dead car. With a lower charge, this is safer in case you touch any bodywork and short out the dead battery. Next, connect the other end of the same jumper lead to the positive connector of the donor battery. Next, connect the black jumper to the negative (-) or black connector of the donor battery. Finally, connect the other end of the black lead to a piece of bodywork or exposed metal on the dead vehicle, away from the battery. When you connect the last connector, this can create a spark, so making the final connection away from the battery is the best way. Next, start the donor car, and allow it to run for a few minutes, charging the dead car for a bit. Next, attempt to start the dead car. If it fails, don’t keep trying to start the car: allow the battery to charge further. Keep an eye on the jumper leads, and ensure they don’t get hot. Jumper leads are designed to carry a lot of current, but may not be able to handle starting current. After starting, allow the dead car to run for a few minutes to allow the battery to charge. Finally, disconnect the jumpers in reverse order, starting with the body jumper on the dead car, the negative jumper of the donor car, the positive jumper of the live car, and finally the positive of the dead car. Again, ensure the jumpers only touch what they are meant to connect to.

Jumper Pack

But what if you’re alone? Jumper packs come in all shapes and sizes and some come with a built in light and tire inflator for more than just dead-battery emergencies. Others, thanks to innovations in lithium technology, are much smaller and can stow away in a vehicle by the spare tire or a small tool compartment. Keep in mind batteries self-discharge, so periodically check the charge, and even consider setting a calendar notification to check the battery. Follow the instructions that come with the battery pack to use it properly. Generally, connect red to positive on the car, black to negative on the car, then switch the pack on. Start the car, then remove the pack.

Battery Charger

If you find yourself able to, you can also use a standard car charger. There are generally two kinds, ‘standard’ and ‘smart’. Older-style chargers, or ‘standard’ chargers use a large transformer. These are robust, but heavy. Newer chargers use special circuitry controlled by a microcontroller, or small computer to check for safety. These are lighter, however they can sometimes prevent you from charging your car, and may break more easily. Following the directions for the charger, clip the terminals to the car battery and body, and start charging. Sometimes it’s best to disconnect the battery from the car, which can be done by disconnecting one of the terminals. Automatic chargers will stop once the battery is charged to prevent overcharging the battery.

Troubleshooting

Sometimes even armed with the knowledge and tools, you still can’t get your car to start. Ensure you make good metal-to-metal contact with the battery and clips. Wiggling the connections can help make a better connection, but ensure there is no power present either with a charger or a jumper pack, or disconnect body ground with jumper cables before doing so. Some jumper cables are of low quality, and can’t carry enough power to even charge a dead battery. A muiltimeter is a useful electrical debugging tool and is a definite way to check if this is the case. A battery that is being charged will be around 13-14 volts. If you measure the dead battery at 12 or lower even while the donor car is connected and running, this can indicate your jumpers are no good.

Final Notes

Be aware to not short out any connections either between terminals, between clips or from one clip to bodywork. This info may not seem useful to electric vehicles, but many electric vehicles also have a 12 volt standard car battery to power the interior equipment, and to enable the high voltage battery, and this battery can be run down as well. Jumping an EV is possible, but ensure you follow the owner’s manual carefully. When in doubt, it may be best to call a service to help you with your car power issues.