The old way of hooking up a voltmeter to a car’s battery and reading the voltage is obsolete. Batteries and Alternators require a lot more to be checked and must be vigorously tested. Each component has to be put to the test to ensure that the vehicle will perform even under the harshest conditions.
There are multiple things that go into checking a battery. Most checks are performed using a load tester that most individuals will not have due to the high cost of equipment. So your local garage is a good start. Make sure they have a battery tester that can load test the charging system. In car batteries it’s important to check the CCA, the battery voltage and to load test the battery. By load testing the battery you are checking if the battery can handle the high drain at any time. A battery requires three times the power to start the car on an extremely cold day compared to a hot summer day. Cold climates play havoc on a battery. Depleted or old cells can fail and leave you stranded at the worst times.
An alternator is necessary to charge the battery. Alternators also have to be vigorously tested from time to time to ensure proper operation. An alternator can be charging perfectly fine just idling and show no signs of issues, but when load is added such as the a/c , lights, and other electrical components it might fail to deliver what is required. Upon testing the alternator it is important to look for signs of failure, abnormal smell, or a dimming of lights or dashboard. A load test is done to check for load at idle and load while driving. The alternator must provide enough charge to maintain and provide more electricity for the high demand electronics in your vehicle.
Doing an inspection of your charging system once a year is recommended by most manufacturers. Batteries will typically last 3-6 years depending on use and care. An inspection and testing can help discover failing components and help prevent a breakdown. Modern vehicles are full of electronics. A good working charging system can power the vehicles and also help prevent premature failure to modules and electrical components.