Jump-starting a car is a common roadside emergency, but what happens when you're faced with a dead battery and only have access to a vehicle with reverse polarity? This guide provides a safe and accessible method for learning how to jump start a car backwards, minimizing the risk of damage to your vehicle's electrical system. This is an advanced technique and should only be attempted if you are comfortable working with car batteries and electrical systems. Improper techniques can cause serious damage.
Understanding Reverse Polarity Jump Starts
Normally, jump-starting involves connecting the positive (+) terminals to each other and the negative (-) terminals to each other. However, in a "reverse polarity" jump start, the negative (-) terminal of the good battery is connected to the positive (+) terminal of the dead battery, and vice-versa. This is usually done when the battery terminals are difficult to access or when there's limited space between the vehicles.
Important Note: This method is not recommended as a standard practice. It increases the risk of damaging sensitive electronic components in modern vehicles, compared to the standard method. Always try the standard jump start method first.
Why You Might Need This Technique
Several scenarios might necessitate a reverse polarity jump start:
- Difficult Terminal Access: Some vehicles have battery terminals tucked away in hard-to-reach locations, making standard connection challenging.
- Limited Space: Parking situations might prevent you from positioning vehicles optimally for a standard jump start.
- Damaged Terminals: If the terminals are corroded or damaged, reversing the polarity may allow for a better connection point, although cleaning the terminals is always recommended first.
Step-by-Step Guide to Jump Starting a Car Backwards
Warning: This method carries a higher risk of damage. Proceed with extreme caution. Always wear safety glasses.
-
Safety First: Ensure both vehicles are turned off. Engage the parking brakes on both vehicles. Never attempt this while either engine is running.
-
Gather Your Materials: You'll need jumper cables. Ensure the cables are heavy-duty and in good condition.
-
Identify Terminals: Clearly identify the positive (+) and negative (-) terminals on both batteries. This is crucial. Misidentification is the most common cause of damage.
-
Connect the Cables (Reverse Polarity): This is where the technique differs.
- Connect the negative (-) cable clamp from the working battery to the positive (+) terminal of the dead battery.
- Connect the positive (+) cable clamp from the working battery to the positive (+) terminal of the dead battery.
- Connect the negative (-) cable clamp from the dead battery to a bare metal grounding point on the engine block of the dead car (far away from the battery). Never connect it directly to the negative terminal of the dead battery.
- Connect the positive (+) cable clamp from the dead battery to the positive (+) terminal of the working battery (it should already be connected to the positive terminal of the dead battery).
-
Start the Working Vehicle: Start the vehicle with the good battery and let it run for a few minutes.
-
Attempt to Start the Dead Vehicle: Try starting the vehicle with the dead battery.
-
Disconnect the Cables (Reverse Order): Disconnect the cables in the reverse order of connection. This helps minimize electrical sparking.
-
Let the Dead Car Run: After successfully starting the dead car, let it run for at least 30 minutes to charge the battery.
Post Jump Start Considerations
- Battery Testing: After jump-starting, it's highly recommended to have your battery tested to determine its condition. A weak battery might need replacement.
- Alternator Check: A faulty alternator can prevent proper battery charging. Consider having your alternator tested as well.
Disclaimer
This guide is for informational purposes only. The author and publisher are not liable for any damage or injury resulting from attempting a reverse polarity jump start. If you are unsure about any step, consult a qualified mechanic. Always prioritize safety. The standard jump start method is always the preferred and safer approach.
