A “flat battery” is one that has lost its electrical energy and has left you stranded in a parking lot or along the side of the road. There are many things that may contribute to this problem, but the seven most common are:

1. The battery has reached the end of its useful life. 
   

   Most batteries will survive five or more years of service in the average car. There are few signs that the battery is about to fail until it suddenly does not start the car or the car stalls. Recharge may help, but replacement may be necessary.
   
   

2. The battery is faulty or defective. 

   Some new batteries are defective due to a manufacturing error. Some brands of batteries are believed to have up to a 7% defective rate within the first year of usage.
   
   

3. You have left the headlights on. 

   Although many cars have headlights that automatically turn off after a few minutes, there are still many on the road today that will not. Be certain your headlights are off as you walk away from your car.
   
   

4. The interior lights did not turn off. 

   As with the headlights, many cars will automatically turn off the interior lights, even if a door is left ajar. Make sure the interior lights go off before walking away. It could save your battery.
   
   

5. The electrical load on the battery is too great. 

   Usage of multiple electrical accessories while the car is parked and the engine is off could run down the battery. If you plan to park for awhile, leave the engine running or turn off high-drain electrical accessories such as interior lights and other devices.
   
   

6. Temperature extremes can affect the life of your battery. 

   Whether the environment your car is operating in is very cold or hot, the ability of your battery to operate at maximum capacity can be affected. Lengthy exposure to temperature extremes will almost always have an effect on the longevity of any car battery.
   
   

7. The alternator is not functioning. 

   This small device is found near the engine and charges the battery while the engine is running. Alternators will commonly last for several years, but at some point will fail. An indicator light on the dashboard of most cars can let a driver know when there is insufficient charge flowing back to the battery. Have your alternator and battery inspected immediately after the first signs of battery failure.