How to Know When Your Car’s Battery Has Gone Bad


Finding a dead car battery is usually not actually a sign the battery has gone bad, since accidentally draining your own battery is quite easy under a lot of circumstances. Most of the time, it just means an accessory or light was left on. Sometimes, it’s because of an electrical problem in a related part, like when the ECM has a short that causes it to draw on the battery even when the engine is off. It can also happen because of an underperforming alternator or voltage regulator. So how can you determine if it is the battery itself?

Bad Battery Symptoms

Whether you’re talking about a car or motorcycle battery, the early symptoms are easy to miss. You don’t generally notice a small drop-off in storage capacity, for instance. Unless you’re testing the battery regularly, you’re also not likely to see a drop in voltage that stays within the overall performance tolerances, but a decline in the battery’s voltage out is a good sign it is coming up on the end of its life. So, if the symptoms are a bit hard to spot, then how do you figure out whether your last encounter with your Duralast jumper cables¬†was due to the battery or just to chance.

Signs A Car Battery Is Goin Bad

Luckily, while the actual symptoms of a bad battery can be hard to spot, the changes in your vehicle’s performance are not. If the battery is losing its overall capacity or otherwise heading toward the end of its life, one of the first signs is the dimming of the headlights and dash backlights when you brake. The alternator keeps everything powered up when you are at speed, but deceleration necessarily causes a drop-off in its power generation, so that leads to dimming. You can also see it if switching on your bright lamps causes the interior lights to dim. Either way, it’s the same basic sign of diminished performance, because the battery isn’t stepping in to pick up all the slack from the alternator’s drop-off.

Frequently finding the battery too low to start but not too low to power lights or accessories can also be a sign the battery is going bad, since it indicates either a charging issue or a diminished storage capacity. You can tell whether it’s an issue charging and retaining a charge or an issue with the alternator by having them tested by a professional at an auto parts store with free battery testing. If your battery is bad, you’re going to need a new one, but that’s not a hard project to take on yourself. Check out the guide if you need to learn how to install a top post car battery for the first time. It’s a quick read, and you’ll see just how simple the process can be.

How Often Does a Battery Need To Be Replaced?

Car batteries can vary widely in their performance, but in general it’s a good idea to replace them about every five years, even if you don’t think they are showing signs of diminished performance. While some batteries last considerably longer, older batteries are much more prone to seemingly random malfunctions that turn them bad, sometimes suddenly.