"Witz, wake up! My car won't start!"
It was 5:10 a.m. on a cold, snowy Monday morning. My wife had to leave for the airport to catch an early flight. But her car's battery was dead. We all like to talk, read and learn about advanced batteries for EVs these days, but how often do we think about the (usually) trusty old PbA lumps we rely upon to start our conventional cars? And the electrical systems they drive?

Pulling on some clothes, I recalled the story we had recently seen on PBS TV's "MotorWeek" about jump-starting batteries in modern vehicles. Car-care expert Pat Goss had held up a set of conventional jumper cables and said, emphatically, "Throw these away!"

Why? Because they can damage your vehicle's electrical systems. Really? The few times I had jump-started a battery in recent years, my old cables had worked just fine. Goss had shown a professional auto shop system and demonstrated a set of new Smart Jumper Cables (PDF FAQ) from tiremaker Michelin, and I remembered that Michelin had sent me one to evaluate.

Read on after the jump to find out what happened that early morning.

My wife had found the new Michelin cables and had her car's hood up when I reached the garage. I popped the hood on the Audi S5 press car I was driving at the time, which was parked next to it. No sign of a battery. Must be in back. I popped the decklid while she checked the Audi's owner's manual. We found it buried deep in the trunk under the temporary spare.
I removed the spare, started the Audi, drove it out into the snow and backed it close to the nose of her car. The cables reached with ease, and – with polarity sorted out within the surge protector at their center, as Goss had explained – there was no concern about which clamp to attach where: one to a battery-positive connection, the other to a solid ground on the dead-battery car; same thing on the running car. The heavy-duty cables stayed flexible and tangle-free despite the bitter cold, but the spring-loaded, insulated clamps took a strong hand to spread. I'm not sure everyone could manage them.

Once all four clamps were in place, the unit's two LEDs were lit to show that everything was cool. She cranked her car, and it started right up. I removed the cables, put the Audi back into the garage, and she was on her way. The whole process had taken about 20 minutes. (Yes, I could have taken her to the airport, but no need – she's an experienced, accomplished driver. Battling Monday morning traffic and fast-accumulating snow, she made her flight.)

Image: Evil Erin - C.C. License 2.0

Then I wondered how serious Goss' warning really was. Were traditional cables likely to damage a vehicle's electrics, or was using them advisable just in case? So, I contacted him.

"I would consider the warning to be quite strong," Goss explained. "Back before computers and sophisticated electronics on cars, there wasn't much of an issue other than folks getting hurt from exploding batteries. Today is a very different world, and there are thousands, if not millions, of cars damaged by old fashioned cables every year."

Here is why: You hook up the old-style cables properly and get the car with the dead battery started. At this point, there is one vehicle with a strong battery and one with a dead one, both running, so both alternators are working hard trying to charge the dead battery and replenish the energy drawn from the good one.

"As long as the cables are connected," Goss continued, "the two batteries act as buffers to contain maximum voltage rise. But as soon as the first cable end is removed, the systems go nuts. When the first cable is removed, the voltage reference is gone. It instantly changes from the level of two batteries and two alternators to one battery and one alternator.

"During this period of adjustment, the voltage regulator allows the alternator to climb to a very high voltage level. The alternators of both cars are unregulated for a few milliseconds, and during that brief time, the alternator can produce several hundred volts of low-amperage electricity. This high-voltage spike shoots through the electrical systems of both cars."

The effect is like a voltage surge running through a computer. It rarely destroys anything instantly but can weaken components of both vehicles, including engine control computers, alternators, sound systems or any of the dozens of electronic modules in modern cars, and there are usually no immediate symptoms because these parts are merely weakened.

But as the vehicles are used, those weakened components will eventually fail. And since those failures may be weeks or months later, you'll probably never realize that it was caused by your use of conventional jumper cables.

Goss explained that "smart" cables have built-in surge protectors like the professional units used in auto shops, which dampen voltage spikes to prevent surge damage to electronics. They also have automatic polarity adjustment to eliminate the possibility of sparking or shorting that can result from hooking cables up backwards, positive to negative.

But why do car batteries go dead, often without warning, and how often is that likely to happen? Many factors can cause a battery to fail," says Alexia Hayes, a product development engineer for Pylon Manufacturing Corp., the aftermarket supplier responsible for distributing and marketing Michelin Smart Jumper Cables (and premium wiper blades) in North America. "The combination of performing many starting cycles, coupled with short run times, can leave a battery below the ideal charge specification for most of its shortened life."

That multiple-short-trip duty cycle pretty much sums up the working life of the typical family vehicle. Then there are temperature extremes: the life expectance of a typical auto battery is three to five years in average climes, but just two to three in areas with high heat or extreme cold. Not to mention the ever-present possibility of leaving lights (or something) turned on when the vehicle is parked -- which none of us would ever do, right?

What about jump-starting a gas-electric hybrid? "You don't jump start most hybrids because the conventional 12-volt battery is not used in the starting process," Goss explained. "The gasoline engine in most hybrids is started by the electric drive motor [powered by the hybrid battery]. The conventional battery only provides power for lights and accessories.

"However, there are a number of different hybrid systems on the market, so the driver should always read and follow all instructions and warnings in the owner's manual." He added that should a so-called "mild hybrid" use the conventional battery as part of the starting process, jump starting would be the same as with a non-hybrid." So, use "smart" cables.

But what if the battery pack in a Toyota, Ford, Chevy, GMC or other "full" hybrid is so depleted that it won't start the engine? "That can and sometimes does happen," Goss said, "but no booster cables here. That requires a specially trained technician due to the high voltage of the hybrid battery, which usually hovers somewhere around 300 volts. That means special training is imperative, as are special high voltage gloves and procedures.

"Here again, carefully read and absolutely follow every instruction in the owner's manual. And, above all else, NEVER touch the orange wires. Grab the wrong wire on a hybrid and you could be killed instantly...like shoving your hand into the wires behind the protective panel on the breaker box in your house...except there's nearly three times more voltage."

My mission here is to enlighten you about the potential risk in jump-starting modern vehicles with old-style cables, not to sell you Michelin's (patented-technology) "smart" ones. I do recommend checking them out (about $40 at stores) as well as suitable alternatives. But, given our recent experience, we will keep our new Michelin set and toss our old ones...except maybe one good set for occasional use on older (non-computerized) vehicles.

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