Skip the auto shop - Our mechanics make house calls

The Top 5 Things That Will Drain Your Battery

battery drain

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. But how did this happen? There are five main causes of car battery drain or failure.

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 or didn't completely close the trunk. 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.

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, parasitic drain can exceed what's normal and deplete the battery.

Bad 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. Then you’ll be stranded at roadside with a stalled car that needs a boost. And even then, bad charging will drain your car’s battery. A professional mechanic will be able to diagnose what's causing a charging problem.

Defective alternator diode

A car alternator recharges the battery and powers certain electrical systems. If your alternator has a bad diode, your battery can drain. The bad 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.

Old battery

If your battery is old, it might not hold a full charge. If your car consistently won't start, it’s possible that the battery is worn out. You should generally replace your car battery every 4-5 years. If your car isn’t starting consistently, and your battery is old, battery replacement should be the first thing you consider.

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 is the battery or something else in the electrical system.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...
The Traveler’s Guide to Driving in Malaysia
CraigBurrows / Shutterstock.com Malaysia is a popular destination for many tourists today. The country has amazing sights and attractions that you will want to explore....
Veteran and Military Driver Laws and Benefits in New Mexico
The state of New Mexico offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch...


Related questions

Q: Alarm preventing battery installation

Yes, this can be an issue with the Tundra. You should be able to hook up the battery and hit the unlock button and then start the truck to reset the the alarm. The alarm also should reset itself after...

Q: I cannot get my bluetooth to work

Hello, having a convenience feature not working properly can be annoying, especially when it has to do with the entertainment system. It appears that Mazda has recognized this issue in Technical Service Bulletin (TSB 09-008/15) to resolve issues with the...

Q: battery light

You will need to have the computer checked for the charging system problem since the alternator is controlled by the computer. I have seen many aftermarket alternators controlled by the computer not work correctly and you may have to get...