This common question might seem like an easy one; but we’ll be sharing several ways that modern vehicles have made the answer more difficult for you, the driver; and for your repair facility.
Vehicles of all types have been equipped with batteries, in some form, since their invention. Most of us are familiar with the idea that the battery in the vehicle does the job of starting the car. It does so by providing electrical power to a small motor, that then turns the engine in the vehicle fast enough to allow starting.
That was ALL the battery did up until the 70’s and 80’s when computer controls began to make their way into cars and trucks.
With the advent of computerized controls, and electrical accessories such as power doors, and windows; the electrical demand on cars jumped up. More power was required than the normal electrical system could handle, and batteries started getting more output, larger in size, with greater capacity to crank the engine AND handle all the electrical loads. Vehicles switched from generators to alternators to compensate for a need to charge these much bigger batteries.
Now the battery was storing enough power to crank the engine, AS WELL as being able to run the electronics and electrical parts in the car.
Fast forward to today, and the amount of electrical motors, switches, buttons and gizmos in a BASIC 2020 Chevrolet Cruze is astounding. There are 20+ computers, multiple power modules, relays, and even a full fledged computer network. The vehicle is often running multiple of these electrical items at once, even when not fully in use. Modern vehicles like this can take up to 45 minutes to an HOUR to fully shutdown the electronics even AFTER you remove the key.
Many of these electronics and computers are sensitive to voltage fluctuations and power losses, just the same as your home computer.
Some of the systems in these vehicles are monitoring for power changes of LESS THAN A HALF A VOLT.
There are many times where a vehicle can suffer strange electronic or computer issues, due to these minute power fluctuations, but the vehicle may still start. These ‘gremlins’ are the harbingers of battery failure, and are the first line of defense against being stuck somewhere with a car that doesn’t start.
A well-trained service technician knows to test your battery, for several different output measurements, and perform a stress test on it. They will use the results of these 3-4 tests to determine whether to recommend you change your battery BEFORE it becomes a problem.
So the next time someone suggests you replace a battery, remember, it wears MANY hats nowadays. So just because it starts the car, doesn’t mean it’s still ‘good’.