A battery that is wearing out seldom fails without warning. It tends to show itself on cold mornings, in the way the engine turns over, and in small electrical behaviour that is easy to dismiss. Logging those signs early gives you something specific to take to a shop, instead of a car that will not start on the day it matters.
Know the sound of a slow crank
A healthy start is a quick, even turn of the engine. A slow crank is a turn that drags, sometimes with a lag before the engine catches. It is most noticeable after the car has sat overnight in cold air, and it may ease on warm days. Note when it happens, not only that it happened.
Watch the dashboard and the electronics
Dim interior lights at the moment of starting, a clock or radio that resets, or a warning message that appears and clears can all point toward the battery or its connections. The same signs can come from a loose cable or a charging fault, so the log is what narrows the cause.
Keep the log short and consistent
Each time you notice something, write the outside temperature, whether the car had been driven that day, whether the trip was short, and what you heard or saw. After a few weeks the entries show whether the pattern is growing. Bring the log to the shop, and ask them to record the test reading and print it for you.
Check the federal records without over-reading them
If you want to know whether complaints or recalls exist for the line you own, the model page lists the federal blocks where they have been pulled. A count beside a complaint is a count. It is not a rate, and it does not tell you what your car will do. Use it to decide what questions to ask, not to reach a verdict.