What can drain a car battery when the car is off?

Even while your car is off, your battery provides power to things like the clock, the radio, and the alarm system. … What may drain a car battery when it’s off are things such as interior lights, door lights, or even bad relays.

How can I tell if my alternator is draining my battery?

How do you diagnose a parasitic drain?

How To Diagnose the Battery Drain
  1. Step 1: Remove Negative Battery Cable. Negative Cable Removed. …
  2. Step 2: Check the Draw Across the Negative Cable and Battery Post. …
  3. Step 3: Remove and Replace Fuses. …
  4. Step 4: Isolate and Fix the Issue. …
  5. Step 5: Replace Negative Battery Cable.

Why does my car battery keep dying overnight?

Some of the most common reasons for a car battery to die repeatedly include loose or corroded battery connections, persistent electrical drains, charging problems, constantly demanding more power than the alternator can provide, and even extreme weather.

How do you stop a parasitic battery from draining?

You can avoid parasitic drain on your battery by unplugging optional equipment such as cell phones and chargers when you park your vehicle for the night. You can also turn off every light in your vehicle and make sure that your trunk, glove box and doors are all fully closed and latched before leaving your vehicle.

What causes parasitic drain on car battery?

The most common causes of parasitic drain are under hood lights, trunk lights, headlights or glove box lights that do not turn off when the door is closed. Relay switches that are stuck in the “on” position can also cause a battery to drain.

What is normal parasitic drain on car battery?

A normal amount of parasitic draw for newer cars is between 50-milliamp to 85-milliamp current draw. A normal amount of parasitic draw for older cars is a reading less than 50-milliamp. Anything past these amounts indicates an electrical issue and should be addressed by a mechanic.