Being in my sixties, I have jump-started plenty of cars. I’ve always known to be careful about reversing polarity, but I’ve never known why it was so important. So I did some research. Now I get it. Reversing polarity when jumping a car is a serious problem. It is so serious that modern portable jump starters tend to have built-in safety features that protect against reversed polarity.
How Current Moves Through a Car
A car’s electrical system is a complex network of wires, fuses, electronic control units, and more. It is all arranged in a direct current (DC) setup. DC power arrangements are essentially closed-loop circuits that send current in one direction only. Here is the thing: it is important that the current move in the right direction. If it moves in the wrong direction, bad things can happen.
When a car is at rest with the engine off, the circuit between the battery and the starter motor is open. Close that circuit, and electricity will flow to the starter. The starter engages, turns the engine over, and gets the car running. Relaxing the key to stop the cranking process opens the circuit and cuts off electricity flowing to the starter motor.
A similar process occurs when you turn on the headlights. Engaging the switch closes the circuit and sends electricity to the lights. Disengaging the switch opens the circuit, and the lights shut off. Everything works just fine as long as current is flowing in the right direction.
Reversed Polarity Means the Wrong Direction
Reversed polarity in an electrical circuit equates to power moving in the wrong direction. If you were to reverse the polarity while attempting a jump start, you would be sending electricity through your car’s electrical system backwards. Instead of the power going directly to the starter motor, it would complete a circuit through the entire system before finally making it to the starter motor at the end.
Why is this a problem? Reversed connections create high-current surges that can be quite destructive. A high enough surge can overwhelm and destroy diodes in the alternator. It can damage electronic control units, other sensitive electronics, and wiring.
Reversed polarity can even generate sparks. If the sparks are close enough to a car battery’s ventilation, they could start a fire or cause the battery to explode. Also note that fuses are of little value in a reverse polarity situation. They will blow, as they are designed to do, but that generally isn’t enough to stop surges from doing their damage.
How to Prevent Reversed Polarity
As mentioned earlier, manufacturers like Clore Automotive tend to build reverse polarity protection into their jump starters. So even though you should be worried about reversed polarity when using a portable jump starter, built-in safeguards are likely to prevent serious damage.
Reversing polarity is a bigger issue during car-to-car jumping. Reverse polarity could damage both cars in the process. So how do you prevent it? By following a standard step-by-step process for jump-starting.
Whether you are using a portable jump starter or another car, start by connecting the positive cable first. It gets connected to the positive terminal on the dead car’s battery. Connect the negative cable next. But don’t connect it to the battery unless absolutely necessary. Instead, connect it to something metal on the car frame. After the car starts, remove the cables in the same order.
Reversed polarity can do significant damage to modern cars so heavily equipped with sensitive electronics. Always be super careful to avoid reversed polarity when jump starting a car. Visit Clore Automotive to learn about jump starters.
