Jump-starting a modern, highly computerized car is a lot riskier than jumping a 1970s-era vehicle. Sensitive electronics are susceptible to damage when the procedure isn’t performed correctly. Not only that, but poor-quality equipment can also increase the risk. One of the biggest risks is something an auto mechanic refers to as high-load kickback.
High-load kickback is essentially a voltage spike or inductive kickback during jump-starting. It sends a sudden, transient surge of electrical energy backward through the target vehicle’s electrical system and into the portable jump starter or running vehicle.
To a professional mechanic, high-load kickback is the enemy. It can damage expensive ECUs and other sensitive modules. And if the mechanic is responsible, he needs to eat the cost of replacing whatever has been damaged.
Why High-Load Kickback Happens
High-load kickback should be simple enough to understand by anyone who took high school physics. When you are jump-starting a car, electromagnetism is in play.
Essentially, a starter motor is little more than a high-powered inductor. As you crank the engine, the starter motor draws an impressive amount of current. It also creates a strong magnetic field within its windings. As soon as the engine fires and the key is released, the electrical circuit between the starter motor and the battery is open. This stops the electrical flow.
Kickback occurs when the magnetic field in the starter motor collapses too quickly. The electricity in this field needs to go somewhere. Unfortunately, that often means surging through the target car’s electrical system as a high-voltage spikes. The voltage can reach 60-100v in some cases.
Why High-Load Kickbacks Are Bad
As you might imagine, electrical spikes are bad news no matter where they occur. But they are especially destructive to sensitive electronic components. That is why you do not want one occurring when you are jumped starting a modern car. High-load kickbacks lead to:
- Frying sensitive components like ECUs, airbag modules, and infotainment systems.
- Ghost failures, scenarios in which modules are weakened but not completely destroyed.
- Damage to a portable jump starter, usually a lower-quality unit sold at a consumer-friendly price.
The damage created by a high-load kickback might not be immediately evident. In a ghost failure situation, for example, a weakened unit could trigger the check engine light. Yet when the car is tested, its problem can’t be accurately diagnosed. It’s not until the module completely fails that a mechanic figures it out.
How the Problem Is Avoided
There is really no way to guarantee no high-load kickback if you’re jumping a dead car using another vehicle. Fortunately, modern auto techs no longer rely on vehicle-to-vehicle jump starting. They use fixed or portable jump starters.
CloreAutomotive.com designs and manufactures a couple of well-known lines of portable jump starters for professionals and DIY mechanics alike. Their units are equipped with transient voltage suppressors or heavy-duty diodes to prevent voltage spikes. If any excess electricity is detected, the units shunt it to the ground before it can do any damage.
Another technique is to turn on a high-draw accessory in the car before a jump starter is disconnected from a running vehicle. This provides an immediate pathway for the excess electricity to flow and dissipate.
Check Those Battery Connections
DIYers should be aware that arcing caused by loose clamps can trigger high-load kickbacks. So whether jumping from vehicle-to-vehicle or using a portable jump starter, battery connections should always be clean and secure.
High-load kickbacks are the silent killer of modern automotive electronics. They weren’t a big problem 50 years ago, but they create all sorts of expensive repair issues for today’s cars.