In this series of Q&A posts, we are using google’s autocomplete function to find the most commonly asked questions about cars and giving them each a definitive answer. This series is ongoing and you can find more of our Q&A articles right here.
Why does my car battery keep dying?
This is a very common question and the diagnosis is very simple once we clarify the situation a little bit. The first question we ask is: Is it dying while you are driving, or will it not start at all?
Your battery is dying while I am driving
If your battery is dying while you are driving, this almost certainly means that your alternator is not functioning. This could mean that you need a new alternator or that the belt that drives your alternator needs to be replaced. The alternator plays a vital role in your vehicle’s charging system. A belt powered by the engines crankshaft generates power that is sent to the battery to keep it charged. For more information, we wrote it up extensively in our alternator article right here.
Your vehicle won’t start at all
If your vehicle won’t start at all due to a battery issue, there are two possible reasons. The first one is that the battery is worn out. Generally speaking, a battery should last from 5-7 years, so if your battery has been in use for this long it would be a safe bet that it needs to be replaced. If you are within the normal life of a battery but it is still not starting it is usually caused by an electrical component being left on and causing a slow drain through the night.
Most vehicles draw some battery current when the key is off, thanks to the clock and the internal memory of engine computers, body-control modules and radio presets. Altogether, they draw a very small amount of current. Fifty milliamps would be a safe upper limit for this, although many vehicles will draw less.
- Popular Mechanics
If it is in fact a slow drain you may need to do some sleuthing to figure out what it is. Common culprits are trunk lights that are not turning off when closed, cell phone/laptop chargers that are not cut off by the ignition, interior cabin lights, the glovebox light, or aftermarket alarms or stereos that are improperly installed. In some cases it can even be caused by a proximity key, the one that unlocks the car for you when you get near and allows for push button start. It works using a radio receiver and any proximity key that gets near it is scanned to see if it has the correct frequency to work the vehicle. If you are in a high traffic area this constant scanning could cause enough drain to render the battery useless come morning, especially if it is near the end of its life.
Bottom Line: If you have a battery problem while driving, bring it in so we can check the alternator. If it won’t start and you can’t determine a cause for a slow drain, bring it in so we can test the battery and see if you need a new one. Contact us here anytime for questions or appointments.