Signs of a Bad Alternator or Bad Battery

When the car suddenly refuses to start or the lights on the dashboard behave strangely, many drivers immediately think about the alternator or battery. And they might be right. Although both are related, their functional properties differ. 

Although both are related, their functional properties differ. However, how can you distinguish between the symptoms and identify the source of the problem? We will examine each component in more detail and focus on the problems associated with their proper functioning.

Difference between alternator and battery 

The battery performs its main and basic task - it stores energy and powers the car's electronic systems. It accumulates charge and transfers it to the starter when the engine is started. For example, it powers the interior lights, multimedia system, headlights and alarm when the engine is off.

The alternator, on the other hand, is the active producer of electricity. It transforms mechanical energy from the engine into electrical energy, ensuring that the vehicle’s systems function properly while driving.While the generator is running, it also recharges the battery.

All in all, the car battery alternator system forms the backbone of the electrical network. The battery provides initial energy to get the engine going, while the alternator sustains power flow once the car is running.

How to tell if my battery or alternator is bad

To determine the condition of either of these two components, you need to pay attention to how the car behaves. If the car stalls shortly after starting, the alternator is probably faulty because it cannot charge the battery. If the engine continues to run smoothly after starting, but then loses momentum, the problem is with the battery itself.

In fact, it is equally difficult to miss the signs of a bad car battery vs alternator. You will quickly notice how the engine’s efficiency drops. 

Common causes of malfunction

Reasons for battery failure include:

• Natural wear and aging after 3–5 years of use.
• Deep discharges caused by leaving lights or electronics on.
• Extreme cold or heat, which damages internal plates.

Causes of alternator breakdown:

• Worn-out bearings that produce loud noises.
• Faulty voltage regulator, leading to unstable charging.
• Broken or loose drive belt.
• Internal short circuits or damaged diodes.

Since the car battery alternator system works as one unit, problems with the alternator will quickly affect the battery, and vice versa.

Battery or alternator diagnosis with inCarDoc

In the past, determining whether the fault came from the alternator or the battery required visiting a service station and running professional tests. Today, technology makes this process much easier. Mobile diagnostic tools such as inCarDoc allow every driver to perform a basic check without special equipment.

To perform the diagnostics, you need to connect the obd2 ELM327 adapter. They support Bluetooth and/or Wi-Fi connection with a smartphone. After certain app and connection settings, users can run the fault code search diagnostics.

Error codes indicate a weak battery, a lack of power generated by the generator, as well as problems with the voltage regulator, etc. The diagnostic app can identify the following fault codes: P0560, P0562, P0563, P0620-P0622. The inCarDoc app provides explanations for each code. The driver can quickly see whether the issue points to alternator problems or battery weakness.

Another benefit of using inCarDoc is the ability to store diagnostic data over time. This history helps monitor gradual changes and notice early signs of degradation before the car leaves you stranded. Timely battery or alternator diagnosis saves money on unexpected repairs and reduces the risk of roadside breakdowns.

Alternator problems or battery issues should never be ignored. If the alternator stops working, the battery will lose charge within a short time and the car will stall. Conversely, if the battery is weak or dead, the alternator cannot start producing energy at all, since it relies on the battery for initial ignition. This close interdependence explains why diagnosing failures can be tricky and why both parts must always be considered together.