How Long Does It Take To Drain a Car Battery?

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Batteries are the most vital part of any vehicle. A battery is installed into a car to convert chemical energy to electrical energy when the user turns on the car’s ignition. The battery also helps in keeping your car sustainable.

The battery provides power to all the components installed inside a car so that they function perfectly. But, the question for us today is, how long does it take to drain a car battery?

How Long Does It Take To Drain a Car Battery?

If you have got a brand new battery, you can expect that the battery holds on the charge for a minimum of two weeks, without the need of charging it. Then, within two to three months, your car’s battery is going to get fully discharged.

Warning for car battery

How Fast Will Your Car Battery Drain, and Why?

A Battery in Average Condition

It will take around 2-3 weeks to get it to drain completely. Even if you remove a negative terminal, it will also die or deeply discharge at 5% per month.

The main reason for batteries to drain even though your car is parked is due to various capacitors and inductors installed in multiple electronics devices in your vehicle. As they never turned off and drew power from the battery.

New Car Load

Today’s newer cars have 75 – 85 milliamps or 0.085 amps of parasite loads (the load on the battery while the car is off). Every 12 hours, this would amount to 1 amp. Multiply it by 25, and in less than 14 days, your battery will be fully drained.

But, of course, a battery needs a lot more power than this, at least 50 percent for starting your car. So your car wouldn’t start anymore after approximately 5-6 days.

On the other hand, a shelf-containing battery would probably be required to recharge after about six months in a controlled 75-degree environment.

Lose Connections

This is also another big reason for battery discharge. Due to losing contact, the current drawn from the battery is higher to feed the requirement. Hence, your battery life gets short.

Sometimes, people leave headlights on conditions that may completely drain your battery due to hurry or negligence.

Jumper wires on car battery

Other Causes

Some other possible causes are satellite radio systems, GPS systems, and an anti-theft system. They act as a parasite and live on the battery.

How Long It Takes for the Car Batteries to Get Discharged?

A fully charged automotive battery can last for up to two weeks before recharging using a generator. After two to three months, this battery will be discharged entirely. You will be unable to start the car engine if the battery is left uncharged for approximately two and a half months.

If you have high-beam headlamps, an entire heater fan, window defroster, seats on, brake lighting, radio on, it’s easy to get 100 amps. However, most car batteries are suitable for an hour for 50 amps, so it takes approximately half an hour for a load of 100 amps.

It’s about the load. Usually, you see a rating called RC on the battery label. This means the capacity of the reserve. The amount of minutes that the battery will last, based on a 25-amp draw, appears in this rating. Finally, you would see Ah on deep cycle batteries, which is another discussion.

Thus, if the label tells Required Charge 60, the battery will be a 25-ampere load for 1 hour. It will take about 5 hours if your load is 5 amperes. 12.5 amperes for 2 hours and so on.

How Do I Keep My Car Battery From Dying When Not in Use?

Do you want to keep your car’s battery safe from battery draining, here are some ways that can help you to keep your car battery fit and healthy.

  • Please keep it in cool conditions: that is parking your car in a shed.
  • You can also increase the life of your car battery by increasing your driving time.
  • Always keep your battery neat and clean.
Car battery diagnostics

How Do I Determine if I Need to Replace My Car’s Battery?

There are various signs that will indicate that it is time to replace your car’s battery. The symptoms are listed down below:

  • Car not starting after several attempts may indicate a faulty battery.
  • Your car’s engine fails to hold the charge; it is a vital sign that indicates problems with the battery or its terminals.
  • Car accessories like radio, AC starts to malfunction. The radio and other components get their share of power from the battery. When the battery becomes faulty, these components do not function correctly.
  • If you smell sulphuric acid evaporating from your car, that is a clear sign that your battery is losing its potential.
  • If you hear annoying clicking sounds while turning on your ignition, when this happens, try jumpstarting. If the jumpstarting fails, perhaps you should consider replacing your battery.

Frequently Asked Questions 

What Are the Potential Factors That Can Drain My Car’s Battery When Not I’m Not Using My Car?

A car or any vehicle has several components and accessories that continue to function even when the car is off. The draining of the battery when the car is off is termed as a “parasitic drain.”

When you turn your car off, the components such as radio, headlights, air conditioning systems are the ones that drain off your car’s battery. So the best way to save your battery from draining is to turn these off when you exit your car.

Watch the video below on how to use a multimeter to perform voltage drop tests to isolate the circuit that is draining your car’s battery.

Is There a Chance That My Car Battery Will Die if I Don’t Drive?

Well, there is a chance for your car battery to run out when your car is not being driven around. This is due to the natural self-discharging processes. You will be surprised to know that driving your car is not the only thing that runs out of your battery, but the accessories installed in your car also drain the battery when you do not drive your car.


Now that you are here reading the conclusion, I hope this write-up was helpful to you. I have tried to serve you with the best information I can. Now, with the above info, I guess you have understood how you keep your battery from draining faster and how long a battery lasts.