Is it normal for the battery to drain every week?

No. New, healthy batteries can last for years, and a weekly discharge usually means an “energy leak” or a failure in the charging system.

In this situation, the battery may still receive charge while the vehicle is running, but it can’t retain that charge when the car is parked—either because of excessive parasitic draw at rest or a real loss of internal capacity.

Parasitic draw: one of the main causes of frequent battery drain

Parasitic draw occurs when the car continues to consume power from the battery even when it is turned off.

Every modern vehicle has a small standby draw to maintain basic functions such as the clock, radio memory, the Smart Key (proximity key) stored near the car, and various electronic modules controlled by the ECU (vehicle’s electronic control unit). This draw is low and normally does not cause problems.

The drain begins when this consumption exceeds normal levels and continuously pulls energy from the battery.

The most common causes of excessive parasitic draw are:

• Misconfigured alarms
• Poorly installed trackers
• Aftermarket or non-standard infotainment systems
• Electrical accessories wired directly to the battery
• Poorly installed non-original accessories
• Electronic modules that fail to enter sleep/standby mode properly

This type of fault explains why many drivers find their battery dead after just a few days without using the car—quite common in vehicles that appear “normal” but keep losing charge over time.

Can limited vehicle use cause the battery to drain every week?

Yes, especially in urban driving.

Very short trips don’t allow the alternator to fully recharge the battery. Over time, this leads to recurring discharges.

This behavior is common in:

• Daily use with trips of 5 to 10 minutes
• Heavy traffic
• Vehicles with many electrical accessories

In vehicles with a proximity key (Smart Key / Keyless), this can also happen because the key prevents the car from fully “shutting down.” The key is constantly emitting or listening for signals, and the car sends radio-frequency “pings” and receives responses from the key.

This creates continuous power consumption even when the car is parked, especially if you store the key at home close to the vehicle.

This usage pattern is directly linked to reduced battery lifespan, as explained in this content about how long an automotive battery lasts.

Can alternator problems cause weekly battery drain?

Yes—and they often go unnoticed.

When the alternator isn’t charging properly:

• The battery never reaches a full charge
• The car runs normally while in use
• After a few days parked, the battery is drained

Common signs include the battery warning light on the dashboard, headlight flickering, and voltage drops when turning on accessories.

In these cases, replacing the battery without fixing the charging system will make the problem return quickly.

Does a worn battery drain faster even without an electrical fault?

Yes.
Over time, the battery loses its ability to store energy, even if it can still start the car in some situations.

A worn battery:

• Appears to charge normally
• Loses charge faster while at rest
• Can’t handle periods without use

This behavior is typical of batteries that already have internal wear, even if they haven’t completely failed yet.

In summary, when your car battery drains every week, the most common causes are:

• Parasitic draw above normal levels
• Vehicle use with very short trips
• Failures in the charging system (alternator)
• Battery with a real loss of capacity

This scenario indicates an imbalance in the electrical system or that the battery can no longer store energy efficiently.

Identifying the cause correctly prevents unnecessary replacements and ensures stable electrical performance in daily use.

On the Tudor blog, you can find other technical content that deepens your understanding of automotive batteries, selection criteria, and performance over time, such as this guide on how to choose the best car battery.