The Top 8 Things That Will Drain Your Car Battery

You're late for work and rush out to your car, only to find that it won't start. The headlights are dim and the engine simply refuses to turn over. You realize that your battery is dead. How did this happen?

A car battery is the most crucial piece of equipment to starting and driving your vehicle. It sends power from the starter motor to the sparks plugs, igniting your car’s fuel, while also giving other systems power. This includes lights, radio, air conditioning, and more. You may be able to tell when your car battery starts to die if you find it difficult to start, have flickering lights, or a weakening alarm system

Your car battery may begin to drain for 8 reasons:

1. Human Error

You’ve probably done this at least once in your life – you come home from work, tired and not really thinking, and left the headlights on, didn't completely close the trunk, or even forgot about some internal lights. Overnight the battery drains, and in the morning your car won’t start. Many new cars alert you if you’ve left your lights on, but may not have alerts for other components.

2. Parasitic Drain

Parasitic drain is due to components in your vehicle continuing to run after the key is turned off. Some parasitic drain is normal – your battery delivers enough energy to keep things, like your clock, radio presets, and security alarm operational at all times. However, if there's an electrical problem – such as faulty wiring, poor installation, and defective fuses – parasitic drain can exceed what's normal and deplete the battery.

3. Faulty Charging

If your charging system isn’t working properly, your car battery can drain even while you’re driving. Many cars power their lights, radio, and other systems from the alternator, which can make the battery drain worse if there's a charging problem. The alternator may have loose belts or worn-out tensioners that keep it from working properly.

4. Defective Alternator

A car alternator recharges the battery and powers certain electrical systems like lights, radio, air-conditioning, and automatic windows. If your alternator has a bad diode, your battery can drain. The bad alternator diode can cause the circuit to charge even when the engine is shut off, and you end up in the morning with a car that won’t start.

5. Extreme Temperature

Whether extremely hot (over 100 degrees Fahrenheit) or cold (under 10 degrees Fahrenheit), temperatures can cause lead sulfate crystals to build-up. If the car is left in such conditions for too long, the sulfate buildup can damage long-term battery life. It may also take a long time for your battery to charge in these environments, especially if you only drive short distances.

6. Excessive Short Drives

Your battery may wear out before its time if you take too many short drives. The battery puts out the most power when starting the car. Shutting off your vehicle before the alternator has a chance to recharge could explain why the battery continues dying or doesn’t seem to last long.

7. Corroded or Loose Battery Cables

The charging system cannot top off your battery while driving if the battery connections have corroded. They should be checked for dirt or signs of corrosion and cleaned using cloth or a toothbrush. Loose battery cables make it difficult to start the engine too, as they cannot transfer the electrical current efficiently.

8. Old battery

If your battery is old or weak, it will not hold a full charge well. If your car consistently won't start, it’s possible that the battery is worn out. You should generally replace your car battery every 3-4 years. If old, or poorly maintained, your battery may die on a regular basis.

What to do with a battery that keeps dying:

Having a battery that won't hold a charge is frustrating, and figuring out what's causing the problem can be tricky. Assuming that the cause of the battery drain is not human error, you will need the assistance of a qualified mechanic who can diagnose your car's electrical problems and determine if it's a dead battery or something else in the electrical system.


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Dan

39 years of experience
965 reviews
Dan
39 years of experience
Honda Civic L4-1.7L - Battery will not hold a charge - Lawrenceville, Georgia
I booked a possible alternator replacement. I bought the alternater. They car was checked out. It was fine. I had a bad O2 sensor pulling amps from a brand new battery. Yourmechanic listed it as a battery check. I got quoted 240$ for the bad 02 sensor...now it is 414$. That is wrong. Dan is a good guy, but this change in price quote it wrong.
Mitsubishi Montero Sport - Battery will not hold a charge - Cumming, Georgia
I've always been "huge" on Friendly Customer Service. Dan was kind and friendly from the time he pulled up to my home. He was extremely patient with me and my many many questions. He provided fast, friendly service to my vehicle. After checking over my car, he was honest in telling me that I needed to take my vehicle to a shop that has specialized testing equipment to better determine what exactly keeps draining my battery where it goes completely dead every 4 or 5 days. So I appreciated his honesty with me. I do recommend Dan for your car service needs. Thank You!!!

Bryant

12 years of experience
585 reviews
Bryant
12 years of experience
Honda Odyssey V6-3.5L - Battery will not hold a charge - Indianapolis, Indiana
He came out to figure out why our battery wouldn't stay charged and found a battery drain. Friendly, great service!
Pontiac G6 - Battery will not hold a charge - Indianapolis, Indiana
I really appreciate bryant he was quick he told me whats wrong and what i meed to do i will be calling for him in the future

Theodore

16 years of experience
1573 reviews
Theodore
16 years of experience
Ford Fusion L4-2.0L Turbo - Battery will not hold a charge - Lynnwood, Washington
He was on time and very helpful couldn't have asked for a better tech to work on my vehicle. Very knowledgeable.

Kenneth

20 years of experience
762 reviews
Kenneth
20 years of experience
Dodge Caravan V6-3.3L - Battery will not hold a charge - Los Angeles, California
He was very knowledgeable. He Explained the possibilities and what needed to be done to find and correct the problem. Very professional and he's a veteran!

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