UniEnergy Technologies Battery » What To Do If Your Car Battery Drained? (Jump Start, Troubleshooting & More)

What To Do If Your Car Battery Drained? (Jump Start, Troubleshooting & More)

A drained car battery almost always catches you off guard, but knowing what you should do immediately alleviates a lot of the stress.

After ensuring your battery isn’t damaged and everything is connected properly, you can use a jump starter or a donor car to give your battery the boost it needs to start the vehicle.

It’s still important to determine why your battery drained and make any necessary repairs if it wasn’t an accident. Keep reading as we explain jump-starting your car, how to determine battery health, and how you can replace your battery on your own.

What to do If the Car Battery Drained?

1. Jumping a Drained Car Battery With Another Car

Step 1: Check if your car battery is safe to jump start

The first step in jumping a drained car battery is ensuring your battery is in decent condition. This is something you should do if you suspect you left your lights on, not something to do if there are obvious signs of damage or leaking fluids.

If you live in a colder area, your battery may not start your vehicle if it is frozen. At this point, the battery swells and the chassis will appear bloated. Do not jump a frozen car battery; wait until it thaws.

Step 2: Ready to jump start

If you’re sure your car battery is safe to jump start, you can hook it up to a jump starter or a donor car using jumper cables. (It’s a good idea to keep jumper cables in your car all the time. Odds are you will need them at least once in your life.)

If you’re using another car, park it across from the front of yours about 1.5 feet away and engage the parking brake. They should not touch at any point, and both engines should be off before you start. 

Connect the cables as follows:

  • Red positive cable to positive terminal on the dead battery
  • Red positive cable to positive terminal on the donor battery
  • Black negative cable to the negative terminal on the donor battery
  • Black negative cable to an unpainted metal surface on dead vehicle (such as the metal strut that holds your hood up)

Start the donor car and let it idle for a few minutes before you start the dead car. If the car doesn’t turn over, wait a few minutes more then try again. You can also rev the engine to increase the alternator output.

When you’re done, leave the engine on and detach the cables in reverse. Make sure they do not touch.

Assuming the jump start was successful, you should let your car run for 15 to 20 minutes before turning it off again. This allows ample time for the alternator to bring your battery to a full charge. If the battery cannot jump start, you likely need a new battery.

2. Jumping a Drained Car Battery With a Jump Starter

A portable jump starter is another useful tool that reduces your reliance on others when this problem occurs. Most have specific instructions to follow, but the general format is to:

  • Connect the cable clamps to the battery terminals (red to positive then black to negative)
  • Connect the other end of the cables to the jump starter
  • Waiting for the indicator light to turn on and for the device to attempt a jump start

Once you receive the jump, disconnect the cables in reverse order. If the jump starter isn’t successful, it will likely stop working to prevent overheating or subsequent damage.

Why Your Car Battery Drained?

Why Your Car Battery Drained
Credit: Advance Auto Parts

Recharging your drained car battery is only half the battle (and it may not even happen if your battery is completely dead). Once you get your car to a safe location, it’s time to determine why it died in the first place.

The most common reasons for unexpected drain include:

  • Leaving an accessory on (usually headlights or interior lights)
  • Parasitic draw
  • Corrosion on cables or terminals that impedes normal charging
  • Letting the car sit without starting it occasionally
  • Issues in your charging system
  • Extremely high or low temperatures

In many cases, your battery is simply worn down and needs routine battery replacement. Most manufacturers recommend replacing your battery every 3 to 5 years to get ahead of the effects of aging and keep your car running reliably.

Left Accessory On

The most common reason a car battery drains relates back to forgetful human nature. Something as simple as leaving your headlights or interior lights on overnight is enough to leave you with a dead battery in the morning.

You can pin the issue on this if you notice your headlights were left in the on position, your interior lights come on when you jump start your car, or if the door was left ajar.

Parasitic Draw

Parasitic draw occurs when an accessory continues pulling energy from the battery when it is not supposed to.

There are plenty of ways to test for a parasitic drain, but the most straightforward involves a digital multimeter.

Turn your car off and remove all plugged in accessories, charge your battery all the way (to 12.6 volts), then remove the negative cable. Set your multimeter to measure amps, then attach the red lead to your negative battery cable and the black lead to the negative terminal.

If the multimeter reads anything more than 50 milliamps, something is drawing too much power while the vehicle is off. Your next step will be to determine which component is draining your battery and repair it in the appropriate way.

Corrosion Interference with Charging

Battery corrosion, the white, green, or bluish grainy powder that may show up on your battery terminals, is normal to a point. It happens as your battery runs and heats up, releasing hydrogen gas.

A chemical reaction occurs when the gas mixes with the air. A bit of corrosion is normal, and you can easily clean it from your terminals. Follow up with an anti-corrosion spray, and it shouldn’t cause problems in the future.

Excessive corrosion occurs if your battery is overcharging, overheating, leaking fluid, or simply too old. If you clean the corrosion off and it keeps coming back, or notice an excessive amount, it’s a good idea to get your battery checked out.

Car Not Driven in a While

If a car is left alone for long periods of time, the car battery will self-discharge and be unable to turn it over the next time you try.

If you have a car in long-term storage, you should still start it and let it run for about 15 minutes every two weeks. This keeps the battery at a healthy charge, and it ensures all other components receive adequate lubrication.

If this isn’t possible, connecting the battery to a trickle charger is a good secondary plan to prevent gradual depletion.

Charging System Issues

Your vehicle’s battery is made to supply enough power for your car to start, but your alternator and other parts in the charging system are what keep your car running. They should be able to recharge your battery completely while you drive around.

If there’s an issue with your charging system (or if you only take your car out on very short trips), your battery will not recharge to the necessary level to start the vehicle. Eventually, you will notice issues with your electrical system while you drive and you may park the car only for it to refuse to turn back on.

Symptoms that relate to your charging system include:

  • Dim or overly bright headlights (from inconsistent alternator current(
  • Stalling or trouble starting
  • Malfunctioning electrical components (i.e. radio or air conditioner turning off randomly)
  • Whining or growling (from a misaligned alternator belt or faulty tensioner pulley)

Many auto parts stores and mechanics can and will test these components separately to help you determine the actual problem. This prevents you from replacing a healthy battery while another problem sits in plain sight.

Extreme Temperatures

Batteries are fairly hardy, but (just like us) they have optimal operating temperatures. If you live in an area with extremely hot or cold weather, your otherwise good battery could start acting up.

High temperatures increase the amount of fluid that evaporates from the battery while operating, and they make it easier for the voltage regulator to overheat/overcharge your battery.

On the other hand, lower temperatures have more short-term effects. They thicken engine oil, making the battery work harder to start your car, and reduce the rate by which your battery recharges.

Storing your car inside or at least under a cover can prevent premature aging or temporary setbacks.

How to Replace a Dead Car Battery on Your Own

If you determine your battery needs replacement due to age or damage, you should replace it as soon as possible. Many battery retailers will replace the battery for you, but if you want to do it on your own:

  • Purchase an appropriately sized battery for your vehicle
  • [Optional] install a temporary power source to avoid losing presets or PCM-stored data
  • Remove the battery cables (negative than positive)
  • Loosen the battery’s ties and remove the old battery
  • Clean the battery tray of any leftover corrosion, dirt, or debris
  • Install and tie down your new battery
  • Apply anti-corrosion compound to the new battery terminals, then reconnect cables (positive then negative)

Remember to test your battery after installation to make sure it meets the OEM specifications of your vehicle. For most batteries, you want a reading between 13.8 and 14.8 volts while your vehicle runs.


Most random car battery drains are due to human error, but this isn’t always the case. If you find yourself with a dead battery, take the necessary time to determine the root cause so you can prevent the issue from recurring.

Take care of your car battery to prevent premature aging, but don’t take too long to replace it when its time comes. This is the best way to protect your entire electrical system from trickle-down damage.

Are you dealing with a drained car battery and struggling to find the cause? Drop a comment with your details, and we will do our best to help you out.

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