How to Correctly Jump Start a Dead Car Battery
Being stranded with a car whose battery is dead is never fun but if you’re prepared, you should at least have a set of jumper cables in your car emergency kit.
Just because you have returned to your vehicle to find the battery drained does not mean that it is all over. Getting back on the road with the same car is actually relatively easy.
You may be wondering why I am writing about this here on UK Survival Guides but I believe that knowing how to jump start a car is very important and is a very helpful skill to learn.
The most common reason for batteries to run out of juice is down to the owner leaving the engine off with power-consuming components running like headlamps, interior lights, or A/C.
It can also be caused due to extreme cold conditions and when a car is left standing for long periods of times. Older batteries also drain quickly and can go flat when you least expect it.
You only need a set of jumper cables and a second car and you can be back on the road in no time.
Although I mentioned that you need a second car, you actually only need a fully charged battery, whether or not it is in another car is irrelevant.
Here’s a guide on how to jump start a car, assuming that the charged battery is fitted to another vehicle.
The cable connections for jump starting often allow only limited current flow, and the less expensive, smaller gauge cables are even more limited than the better ones.
Depending on how dead the battery is, jumper connections may or may not start a vehicle immediately, and may require a few minutes of being hooked to a running car with a fully charged battery to charge it somewhat.
Be especially wary when jump starting modern cars with engine management systems – careless jump starting, particularly if the cables are allowed to spark, can cause damage to the car’s computer components.
Some cars with remote mounted batteries, such as many BMWs, are fitted with special terminals under the hood to allow jump starting, and on these cars the jumper cables should only be connected to the special terminals provided.
- Position the vehicles close enough so that the jumper cables will reach easily between each battery, but, MAKE SURE THE VEHICLES DON’T TOUCH EACH OTHER!
- Make sure the cables are not in the way of the fan, drive belts or any other moving parts when the vehicles are started.
- Make sure the booster battery is the same voltage as the dead one in the vehicle – Nearly all modern car and truck batteries are 12 volts.
- Make sure the ignition switch is in the off position, and the transmission is in Neutral (manual) with the parking brake set, or Park (Automatic).
- Turn off the lights and other electrical loads on the car with the dead battery, though if it is a modern car with a computer, it’s a good idea to turn on the heater blower motor which will minimize the damage an excessive electrical surge can cause.
- It’s a good idea to wear safety goggles, as there is always a chance of an explosion and batteries are full of acid.
Jumper Cable Order
Follow the steps below in this EXACT order:
- Connect the red jumper cable to the positive terminal of the dead battery (or jump start terminal on a car with a remote mounted battery).
- Connect the opposite end to the positive terminal of the booster battery or jump start terminal.
- Connect the black jumper cable to the negative terminal of the booster battery or jump start terminal.
- Connect the other end of the black cable to a well grounded bolt or bracket on the engine block of the vehicle being jumped, not the battery itself. This prevents sparks near the battery which may cause an explosion.
- Start the engine of the vehicle with the good battery and let it run at a moderate speed to charge both batteries.
- Start the engine of the vehicle with the discharged battery.
- Reduce the engine speed to idle on both vehicles and leave all switches off to prevent damage to the vehicle electrical system.
- Remove the jumper cables in the reverse order they were attached, making sure to never touch the red and black terminals to each other.
If the charging system and the battery of the car which had to be jumped is in good condition, 30 minutes of driving should being it back up to a full charge.
Remember, sometime in extreme cold conditions a perfectly functional car may need a boost to get started because batteries put out less energy the lower the temperature, while at the same time need more power to turn in the cold.