Dead battery. It happens to everyone eventually. You leave the headlights on overnight, or the battery is old and gives out. Knowing how to jump start a car means the difference between getting home and calling a tow truck.
ChrisFix walks through the right way to do it - the cable connection order matters for safety, and most people get the last connection wrong. This takes about five minutes once you know the process.
Pull the running car close enough that jumper cables can reach both batteries. The cars should not touch each other. Turn off both engines and take the keys out of both ignitions.
Pop both hoods and locate each battery. Find the positive terminal (marked with a + and usually a red cable) and the negative terminal (marked - with a black cable) on each one.
Untangle your jumper cables so you have one red and one black end in each hand. From this point on, do not let the clamp ends touch each other.
Clamp the red (positive) cable onto the positive terminal of the dead battery. Wiggle it to make sure the copper teeth grip the metal post. You start here because the dead battery has less energy, so it's the safest connection to make first.
Tip
Set the loose black clamp on a piece of plastic while you walk to the other car. You don't want it touching any bare metal and accidentally grounding out.
Walk to the car with the good battery, carrying both loose cable ends. Keep them apart. Clamp the red cable to the positive terminal. Then clamp the black cable to the negative terminal.
Both cables are now attached to the good battery. Only one connection remains.
This is the step most people get wrong. Do NOT connect the last black cable to the negative terminal of the dead battery. Clamping there creates a spark right next to the battery, which can ignite hydrogen gas fumes.
Instead, find a bare metal bolt or bracket on the engine block, away from the battery. A strut tower bolt or engine mount bracket works well. Avoid anything near fuel lines or moving parts. Clamp the black cable firmly to that ground point.
Tip
Some cars have a designated ground point specifically for jumping. Check your owner's manual. It's usually a bare metal stud or bracket marked with a ground symbol.
Before starting anything, look at where the cables hang under both hoods. Make sure they're not draped over cooling fans or the serpentine belt. A cable caught in a spinning fan will ruin your day fast.
Once the cables are clear, start the car with the good battery and let it idle for two minutes. The alternator charges the dead battery during this time.
After two minutes, try starting the dead car. If it fires up, move on to removing the cables.
If it cranks slowly but won't catch, let it sit five more minutes and try again. You can also have someone in the good car rev the engine to about 2000 RPM while you turn the key. The alternator spins faster at higher RPM, pushing more current to the dead battery.
Tip
If all you get is a single click, the battery might be permanently dead with a shorted cell. Before giving up, double-check that every clamp has a solid connection and try a different ground point.
Removal order is the reverse of connection. Remove the black ground cable from the dead car first. Since it's clamped to the engine (not the battery), any spark happens away from hydrogen fumes.
Then remove the red cable from the dead battery. Walk to the good car and remove the red cable, then the black cable. Keep the clamp ends from touching metal as you go.
