What Causes Car Batteries to Die?

What makes car batteries die?

Car batteries are charged by the alternator while the engine runs, which means there’s usually a constant supply of electricity to your vehicle. However, nothing lasts forever, and car batteries need replacement every few years. If your battery is draining rapidly or completely dead, there may be a few reasons for it.

  1. Your car is off but a light inside has been left on, either by a switch or not properly closing your door, trunk or hood. Your headlights may have been on, as well. Generally, a jump start will allow your battery to function normally again.
  2. You have a bad alternator. Your alternator is an on-board electricity generator converting mechanical energy of the engine to electrical energy. It creates an AC current, which is then converted to DC to charge your car battery. The engine needs to be running/cranking in order for this to happen; a car that is running idle will not charge a battery as well as a car that is being driven. You can check whether or not you have a bad alternator by unplugging the positive connection on your battery; if the car stops, the alternator is bad.
  3. If you keep starting and stopping your car before your alternator has a chance to charge your battery, you will drain more power than you are generating, causing your battery to eventually die.
  4. Your battery is old and needs replacing. This usually happens when the battery is 4 – 5 years old. Batteries degenerate faster if you leave the car sitting unused for a long period of time, not giving it a chance to recharge.