Skip to content Winter, frost, and the engine won’t start? A familiar situation. Many rush to get a jump-start from another car, but a single mistake with the cables can lead to expensive electronics repairs. A jump start is a handy way to start a car with a flat battery, but it must be done with care.
Both vehicles must be parked on level ground and secured before jump starting. Drivers should always check for visible damage to the vehicle’s battery, such as cracks, leaks, or corrosion, before proceeding. If the battery is cracked or leaking, or if there is any visible damage, do not attempt to jump-start and call for professional help or a breakdown service instead.
This is especially true for modern cars packed with sensors and control units. The assisting vehicle must have a fully charged battery with the same voltage as the dead battery, usually 12 volts.
Jump starting a car can be dangerous if not done properly, and doing the procedure wrong may lead to costly repairs or even an explosion. Drivers should always prioritize safety and consult a breakdown service if unsure.
Below, you’ll find a step by step guide to using jumper cables safely.
Here’s a brief guide for you on jump starting a car:
To jump start your car, you need jumper cables (also called jump leads) and a second vehicle with a working, fully charged battery of the same voltage (usually 12 volts). Before starting, check the owner’s manual for both vehicles—especially for hybrids and electric cars, as they often cannot be used as “donors.” Jump leads are a simple tool used to start up any vehicle with a flat battery. They feature four fully insulated alligator clips—two red and two black. The red clips (red lead, red jump lead, red clamp, red jump, end of the red) attach to the positive terminals, while the black clips (black lead, black jump lead, black clamp, black jump, black clip) attach to the negative terminal of the working battery and to an earthing point (unpainted metal surface) on the dead car. Only hold the jump start cable by the insulated plastic handles, and wear protective glasses for safety. The diameter of the jump start cable should be at least 16 mm, and for cars with large engines, 25 mm is recommended.
Perform safety checks: inspect both batteries for visible damage, leaks, or cracks, and do not attempt to jump start if any are found. Batteries produce flammable gases—avoid naked flames and sparks. Never attempt to jump start a frozen battery, as it can explode. If you have a start booster or battery booster pack, you can use it as an alternative to jumper cables. Connect the positive lead to the positive terminal and the negative lead to a good earth point (unpainted metal surface). Keep booster packs charged and avoid storing them in extreme temperatures.
Correct Sequence (memorize!):
CONNECTION:
- Ensure both cars are parked, turned off, in neutral or park, and parking brakes engaged.
- Connect the red jump lead (red clip) to the positive (+) terminal of the working battery, then connect the other end of the red jump lead to the positive (+) terminal of the dead battery.
- Connect the black jump lead (black clip) to the negative (−) terminal of the working battery, then connect the other end of the black jump lead to an unpainted metal surface (earthing point) on the engine block or chassis of the dead car—never directly to the negative terminal of the dead battery to avoid sparking.
STARTING:
- Start the engine of the vehicle with the working battery and let it run.
- Attempt to start the dead vehicle (no more than 10 seconds per attempt). If the engine does not start, wait a few minutes before another attempt, and avoid prolonged cranking.
- If the engine starts, turn on the heater and rear window defroster in the jumped car to smooth out voltage spikes.
- Keep the engine running for at least 30 minutes to recharge the battery, or recharge fully with a charger.
DISCONNECTION:
- Disconnect the black jump lead (black clamp) from the earthing point (unpainted metal surface) on the dead car, then from the working battery—always in the reverse order to how they were attached.
- Remove the red jump lead (red clamp) from the positive terminal of the dead car, then from the working battery.
Improper or incorrect connection of the jump leads can result in costly repair or damage to the vehicle’s electrical components. Jump starting is only a temporary solution for a weak or old battery—repair or replacement may be needed. Regular service and battery checks can help detect issues early and prevent breakdowns. Batteries in modern cars may deteriorate faster due to increased electrical demand, and deep discharge should be avoided to maintain battery health. If the dead vehicle does not start after several attempts, call a breakdown service or professional help.
What NOT to Do:
· Do not allow the positive and negative terminals to come into contact.
· Do not get a jump-start from a hybrid/electric car if prohibited by the manual.
· Do not crank the starter for more than 10 seconds.
· If the dead vehicle does not start immediately, wait a few minutes before making another attempt. Avoid repeated or prolonged attempts, as this can increase the cost of repair and may cause further damage.
· Do not turn off the donor car immediately after a successful start.
After a Successful Jump-Start:
The battery will need to recharge fully. Drive the vehicle normally for at least 30 minutes to help recharge the battery, and avoid using unnecessary electrical consumers (music, seat heaters). For a complete recharge, using a stationary battery charger is recommended.
Jump starting is only a temporary solution if your car battery is weak or old—the problem may reoccur, and the battery may require repair or replacement. Avoid deep discharge of the car battery to maintain its health.
Not sure or afraid of harming your car? Better call professionals – it will save your nerves, time, and budget for repairs.
Car Battery Maintenance
Keeping your car battery in top condition is the best way to avoid the hassle of a dead battery and the stress of emergency jump starting. Whether you drive a personal vehicle or manage a fleet of commercial trucks, regular battery maintenance can save you time, money, and unexpected breakdowns. Here are some essential tips to help you maintain your car battery and reduce the risk of a flat battery:
- Inspect your car battery terminals regularly for signs of corrosion. Clean them as needed to ensure a strong, reliable connection for your vehicle’s electrical components.
- Make sure the battery is securely mounted to the engine block to prevent vibration, which can cause internal damage and shorten battery life.
- Protect your battery from extreme temperatures. Both excessive heat and cold can impact battery performance, so park in sheltered areas when possible.
- Avoid letting your battery discharge completely. Deep discharges can significantly reduce the lifespan of your battery, especially in modern cars and hybrid or electric vehicles. Always follow the manufacturer’s recommendations for charging and maintenance.
- Invest in a quality battery maintainer or trickle charger to keep your battery fully charged during long periods of inactivity—ideal for commercial vehicles or trucks that may be parked for extended times.
- Watch for early warning signs of a failing battery, such as slow engine cranking or dim headlights. If you notice these, have your battery tested by a professional mechanic before it leaves you stranded.
- Keep your vehicle’s electrical components, like the alternator and starter motor, in good working order to prevent unnecessary strain on the battery.
- Store a set of quality jump leads or a portable battery pack in your vehicle, along with clear instructions, so you’re prepared for emergencies.
- If you’re not confident in jump starting or battery maintenance, don’t hesitate to call for roadside assistance or consult a professional mechanic. LKW Help 24 offers 24/7 commercial vehicle roadside assistance and heavy-duty truck recovery across Germany, ensuring you’re never left stranded.
- Always refer to your owner’s manual for specific guidance on battery care and jump starting procedures tailored to your vehicle, especially for hybrid or electric cars.
- When working with your car battery, wear protective gloves and safety glasses, and avoid wearing metal jewellery that could cause accidental short circuits. Make sure the area is well-ventilated and keep away from naked flames or sparks.
By following these maintenance tips, you can help prevent a flat battery and reduce the need for emergency jump starting. Prioritize safety, keep your battery fully charged, and remember that professional help is just a call away if you ever need expert roadside assistance or commercial vehicle recovery in Germany.
