Can An Alternator Drain Your Car Battery?

It’s a beautiful morning. You been preparing for this interview or business meeting for quite some time now. You’re pumped, you’ve given yourself a proper pep talk and you can’t wait to face the lion and show it who’s boss. Nothing can get in your way today.

You walk out the house with reason. Today, you’re going to accomplish what you’ve been working on for several years now. It may be your dream, or not. It could also be something that puts you in the right path.

You get in your car and push the key into the ignition, twist and the starter will welcome you to a new day with a click, or a cough of someone experiencing serious respiratory issues. All your electronics were off, the starter has had no issues and the battery has been working fine. What could the problem be?

Can an alternator drain your battery? Yes, absolutely. This happens whenever your vehicle’s alternator has a bad diode. In normal operation, this diode allows power to flow one way, from the alternator to the battery. A malfunctioning diode will cause power from the battery to flow backwards in the circuit, thus draining the battery.

Whenever you start your car, this drains a lot of power from the battery. To recharge it, the engine, through the alternator, will generate electrical power to be fed back into the battery, and to power other electronics. To prevent the battery from being drained or overcharged by the alternator, employs a diode to prevent this from happening.

What Are the Systems that Your Alternator is Bad or is Failing?

1. Regularly Jumpstarting the Vehicle

Unless you are totally extrovert and have no way to do things other than involve others, every other person would like some degree of autonomy and in the knowledge that they can rely on themselves and on the tools that they rely on to help them get through life.

It’s probably the reason why people start getting a feeling of betrayal whenever their car needs a jumpstart, especially when you want to attend to something urgently and the vehicle is not cooperating.

However, you may notice that your vehicle has recently been requiring an abnormal number of jumpstarts. If it was in good shape, you vehicle would not need any sort of jumpstarting to get it on the road.

However, there is a problem. The usual culprit is the battery. A failing battery will not store enough charge for the next use, or will fail to deliver power to the starter. The battery is what people will most likely replace whenever they are faced with having to jumpstart their vehicles multiple times.

If after replacing the battery you’re still faced with the same problem, then it wasn’t the battery to begin with. It was another part of the electrical circuit; the alternator. The alternator, as mentioned earlier, is responsible for charging the battery and making sure it is ready for the next time you start your vehicle.

A failing alternator will have problems charging your battery and providing power to other electronics and will result in you having to jumpstart your vehicle.

2. Dim Lights

The battery is responsible for providing enough juice to start the car, but that’s not all it does. The battery is also responsible for providing power to the engine’s spark plugs to enable combustion in petrol engines. It is also the backup power system in cases where the engine is off. This is the reason why you can turn on a car’s electronics such as radios, lights and wipers while the engine is off.

While the vehicle is running though, all this work is done by the alternator. The alternator powers the vehicles electronics and charges the battery. As the alternator begins to fail, it delivers less power to the electronics that need it.

As you use more electronics in your vehicle, the power delivered to them will be less. This as already been anticipated by the car manufacturer; therefore, enough power is generated to keep all electronics performing at a high level. The failure of an alternator will mean these electronics don’t perform at their best.

And this is the reason why when you turn on the headlights, they appear dim in comparison to earlier. The more electronics you switch on, the lights keep on getting dimmer. This is an indicator that your alternator is in bad shape, and in dire need of some maintenance.

3. Battery Light on Dashboard

Unless you’re Sheldon Cooper, no one likes that the warning lights on the dashboard keeps coming on, especially not that pesky, orange check engine light. If there’s a symbol of passive aggressive messaging in society today, that would be it.

This time though, it’s not the check engine light that would come on. It would be the illuminated battery light on the dashboard. Now, this light doesn’t come on as often as the check engine light. However, when it does come on, take immediate action, otherwise you risk getting stranded in an unfamiliar location.

Aside from just a cable from the alternator to the battery, the electrical system also comes with a simple circuit that is meant to test how much power the alternator is delivering to the battery. This circuit will frequently test whether the power provided is around 12 volts. If not, the battery light on the dashboard will come on.

Your car will work fine when the light does come on. This is because the battery does hold enough power to last you a while. However, when the battery does drain, that’s where the problems will rear their ugly heads.

If you do suspect that your alternator is having trouble powering your vehicle, then it would be time to head over to your service center to have this all sorted out. If you are adept at using your hands and electrical tools, then you will simply need a voltmeter to check whether the power you’re battery is receiving is sufficient to charge it.

1. Spark plug – Wikipedia
2. Symptoms of a Bad or Failing Alternator – YourMechanic
3. What does the battery light on the dashboard mean? – HowStuffWorks