Red = Positive
Black = Negative
Why do the battery charger cables have to be connected in this order?
The reason why you connect the battery cables to the dead car battery
1st is you have 3 metal cable ends dangling and potentially touching metal car parts, so a dead battery is less likely to cause any sparking, since it has little or no voltage. So that is the safest starting point for your jumper cables.
The
2nd battery cable clamp goes to the positive end of the good battery instead to minimize completing any circuits until we are ready to.
Then the
3rd end of the battery cable goes to the ground of the good battery. Remember, we still have not completed the circuit yet, until the
4th battery cable clamp is attached to ground. This is why this order of attaching the battery cables to your car batteries is the safest way to do it. It minimizes unnecessary sparking until the charging circuit is completed. This is good practice because excessive and unnecessary sparking could cause car batteries to fail.
Since the bad battery is weak, and to
prevent exploding, it's ground clamp gets connected last, but not directly to the ground battery post. To prevent sparking directly on the battery, you connect the 4th battery cable clamp to a metal frame part of the dead car, which is connected to the minus pole of the battery. Car batteries have their ground cable also wired to the chassis of the car, so by clamping to a good metal chassis point, this is electrically equivalent to connecting to the ground post of your car battery.
And get a good set of jumper cables to keep in your trunk at all times..you'll never know when you need it 
Cheerz
