Updated at: 28-07-2022 - By: Lucas

If you have a car, you know what it’s like to wake up to a dead battery in the morning. When you don’t know what’s causing it, this can be really inconvenient. There are a variety of reasons why an automobile could seize or grind to a halt instead of starting slowly in the morning.

Most of the time, a low-pressure battery is the culprit when the voltage has dropped too low to start the engine and needs to be recharged.

At night, does your car’s battery lose power?

The battery can be drained by electrical equipment left on overnight, although this isn’t the only reason.

Why does car battery voltage drop overnight?

Several factors can cause the battery of an automobile to lose power over night. Your car’s battery might discharge even after shutting down the engine for a variety of reasons, the most common of which being issues with the battery’s power, parasitic drain, or an outdated battery.

Causes why car battery voltage drops overnight

Car Battery Voltage Drop Overnight-2

Your car’s battery dies overnight because of the following reasons.

1. Accidentally leaving the car ignition on

Ignition systems drain a large amount of battery power if left on overnight. Leaving the lights on for long periods of time will quickly drain the battery.

2. Leaving electrical accessories on

There are a number of electrical components in automobiles that can be left on by accident. Interior dome lighting and the radio are two examples of this. When left on and even when switched off, these devices can use a lot of power.

3. Batteries often self-discharge

A battery’s capacity to store a charge is never guaranteed to be 100 percent. Even if no appliance is attached, batteries can typically deplete on their own.

However, a 55AH battery can lose only 0.1 percent of its capacity over the course of a single night.

4. Poor connections at the terminals of the battery

Batteries that aren’t properly attached to the terminals can affect the battery’s ability to charge. It’s possible that you won’t be able to start your automobile in the morning if the batteries are disconnected.

5. You might be taking your car on shorter trips.

The battery in your automobile is not designed for short trips. To properly recharge your car’s battery, you must take a long road trip. You can charge the battery by doing small excursions and leaving your vehicle in the parking lot for an extended period of time.

6. A failing or bad alternator

Using a digital meter and the battery at rest, an alternator in good working condition should produce roughly 14.5 volts. If the voltage is too low or too high, this is a clear sign that the filter is defective.

7. Aging or old battery

When a battery starts to discharge, it’s time to replace it. Batteries lose their ability to hold a charge as they get older. Because of this, these outdated batteries have a significant likelihood of losing their charge over the course of a single day.

Check your battery’s CCA output to make sure it’s what it’s supposed to be. It’s time to replace the battery if it’s only able to supply a fraction of what it’s supposed to do.

8. Parasitic drain

A parasitic drain is another prominent reason of a power battery’s overnight discharge. Even after the engine is turned off, parasitic drain continues to drain the battery.

Even when the engine is off, the battery in the automobile keeps the anti-theft system and the clock running. Battery power is used to charge other parts that do not need to be charged after the engine has been shut off, causing a drain on the battery.

It’s possible that you left your headlights, cabin lights, and glove box lights on overnight, among other things. Poor battery installation, inadequate wiring, and faulty fuses can all cause parasitic drain.

9. Temperature extremities

When it’s too cold outside, the car battery can suffer if it’s left on the road. Chemical reactions in a battery will be affected by the cold if the battery is left unattended for a lengthy period of time.

When it comes to the car battery, warmer weather might also have an impact. When it’s hot outside, the chemicals in your car battery will evaporate, causing it to lose power.

If you reside in an area where temperature extremes are common, it is imperative that you keep your car in a well-ventilated location.

Is it normal for a battery to drop voltage overnight?

No, the charge in a car battery should not be lost over night. Despite the possibility of some voltage being lost, it is unlikely to be significant. If you’ve noticed that your car’s battery is draining overnight, there’s probably something wrong.

How much voltage should a car battery drop overnight?

A car battery shouldn’t drop below 0.3 volts overnight, but there is no rule for determining this.

How to fix the Car Battery from Draining Overnight?

Car Battery Voltage Drop Overnight

Overnight, you can fix the problem of the car discharging by

1. Switch off all electrical appliances

If the music system and other electrical accessories aren’t turned off, they can consume a lot of electricity.

2. Replace the car battery

Get your car battery tested by a certified auto technician to see if it can supply the necessary powerPower. If you see any indicators of failure, like as a sluggish start, you should have it replaced right away.

3. Connect your car battery to a maintenance charger

Maintaining your car battery’s charge is necessary if you’re using a lot of gadgets while driving.


When you have to drive somewhere first thing in the morning and your car won’t start, it’s even more frustrating. Only if the power drains are not considerable is it usual to experience power losses during the course of the night.

If you detect voltage reductions, the most typical power drainer is electrical accessories still turned on in the vehicle.

Furthermore, if you have multiple accessories attached to your vehicle, the battery’s power intake may be slowed, and the battery may be completely depleted as a result. As a result, it is imperative that you use a maintenance charger.