“A faulty battery can do more damage than you think,” says Chris Muir, mechanic and professor at Centennial College. “Battery problems can lead to a damaged – or destroyed – alternator, which means you’ll be facing even more costs.” The battery is an electrical reservoir; surges of power, like blasting defrosters or using the horn, come from it. After the battery starts the engine, the alternator replaces that charge. A battery that isn’t taking the alternator’s charge is forcing the alternator into overtime, and putting the alternator in the line of fire for demand surges. A weak battery shortening the life of an alternator just means higher repair bills.