Your car’s electrical system depends on a battery for power and an alternator for charging that battery. When you turn the ignition switch, the battery is activated to turn on the starter motor that turns the engine.
Of course, while the engine is running, the crankshaft is also turning the alternator, assuring that the battery is being charged while you drive.
Generally, when you start the engine, the battery light comes on very briefly and then goes out. If that annoying battery light remains illuminated while you drive, there could be a fault with the charging system.
So, if the battery light insists on accompanying you on your journey, you need to take notice and be aware of what possible problems could arise.
The Basics of Conventional Vehicle Batteries
Batteries can only store a finite amount of energy to keep the vehicle and its accessories operating. The stored chemical energy in the vehicle’s battery allows it to start initially and then recharge while running.
The recharging is accomplished when the crankshaft pulley rotates the alternator belt, referred to as the serpentine belt or accessory belt, which causes a rotor inside the alternator (known as a generator) to spin.
By taking the kinetic energy from the rotating pulley, the alternator converts a portion of that energy into AC power (alternating current). The AC power is turned into DC (direct current) power, which is stored in the battery.
This energy allows powered accessories such as headlights, power windows, heated seats, radio, air conditioner, DVD players, and cell phone chargers to function.
Note: An older vehicle may use a dynamo (known as a DC generator) instead of an alternator.
The voltage regulator keeps the voltage at the desired amount during the time the battery is being charged, and typically is part of the engine control unit (ECU).
Current (made of electrons) flows from one post of the battery through the accessories, and back into the battery through the other battery post.
The vehicle has wires around the engine bay called ground straps that connect bits of the wiring harness to the chassis, and that helps complete some circuits.
What Does The Battery Light Mean?
Your battery light, or dashboard battery indicator, is intended to inform you of a problem with your vehicle’s battery or charging system. It could be that your battery is worn out, or damaged, or that there is a fault with the charging system.
First things first, if the battery light illuminates when you turn on your car, you likely don’t have anything to worry about. It is completely normal for a battery light indicator to illuminate when turning on a car and then turn off in a few seconds. So if you see that, then ignore it.
If you notice it is turning on and then turning off again when you are accelerating, that is possible because there is no power coming in from its source (the alternator), and that can also be caused by either a loose battery connection or a broken serpentine belt.
If the light stays on while you are driving, however, pay attention. You will likely see other symptoms of weak or no charge to the battery, too. You may see that the radio won’t turn on, or the power windows take too long to come up.
An illuminated battery light may be from several possible issues, including:
- Loose or corroded battery cable
- An issue with the alternator or voltage regulator
- Damaged cells or plates in the battery
- Faulty wiring in the car’s electric charging system
A dashboard battery light means there is a battery charging issue. Your car is not getting enough voltage from the car battery to run. It needs more “juice”!
9 Reasons Why Your Battery Light Comes On
Every time the vehicle starts up, you should see the battery warning light turn on briefly, and then back off within a few seconds. This is a system test to ensure the battery light on the dash is working as well as any components of the charging system that are being monitored.
If there is a fault in the charging system, the warning light for the battery will stay on. If this is the case, there are a few places to look, in no particular order, when troubleshooting.
Safety is important when working on electrical systems, so refer to your owner’s manual for general information.
It is smart to wear gloves or goggles when working around the battery in case battery acid is splashed, as well as rubber gloves for shock protection. You want to be sure to always disconnect the battery before cleaning or inspecting it closely.
If the battery is struggling to charge, you should see symptoms such as dim headlights, your clock running slow, as well as features such as the air conditioning and radio not working.
#1. Bad Battery.
Normal 12-volt batteries have a lifespan of 3 to 5 years. Some manufacturers have claimed, in writing and sales pitches, a longer lifespan, but a long life should not be expected.
These batteries have a lead dioxide plate and a lead plate submerged in an electrolyte solution made of sulfuric acid in each of six cells.
The cells or lead plates can break down over time, and the electrolyte solution can start leaking out of the battery. If this happens on a battery you have, the battery must be replaced. Additionally, bad wiring or bad grounds can also affect the ability of a battery to take or hold a charge.
#2. Bad Alternator.
It is easy to check to see if an alternator is functioning using a multimeter. First, set your multimeter to the DC voltage setting (which is what alternators produce).
The voltage values for a good alternator will be between 13.6 volts and 14.6 volts. If the voltage is less than 12 volts, then it will trigger the battery light, and it might be that the alternator must be replaced.
If the voltage regulator is not working, that could be the problem, I don’t say this lightly, but with the understanding that a voltage regulator limits the output to a safe level of 14.5 volts.
#3. Bad Alternator Belt.
An alternator belt keeps the alternator, engine, and accessories all together, so having one that works is essential. The belts can be cracked from age and in some cases completely broken. Belts can also be placed too tightly, have alignment issues, or be too loose.
If the battery light comes on due to a bad alternator belt, or in conjunction, when the vehicle is running, it could cause squealing noises from under the hood.
#4. Corroded Battery Terminals.
The battery posts are the channels for electricity and should not be covered with any other substances that can increase resistance.
Corroded electrical components are not very good conductors of electricity at all. Corrosion is often a major source of bad connections in an otherwise healthy electrical system.
Corrosion produces the white, blue, or green buildup that results from either a reaction that happened in normal use or from a buildup of persistent heat. Because of the additional heat we are always talking about, hot climates will have more corrosion on electrical components, including vehicles.
Corrosion is an acidic substance that will eat away at a vehicle’s paint and could irritate skin. Be careful and use a pair of gloves. Typical rust will have a reddish tint and may also adversely affect conductivity in electrical components.
If you see corrosion on your battery terminals, put on your PPE (Personal Equipment) and clean the terminals with a stiff-bristle brush and a solution of 1 tablespoon of baking soda dissolved in 1 cup of water.
The solution is alkaline, so it will neutralize the acid in the corrosion. Battery terminal cleaners are specialized brushes designed to clean the battery post, terminals, and the inside of the terminals. They are inexpensive, and they may make your job a little easier.
#5. Loose battery cable.
Battery cables should be snug around the battery terminals to provide a good connection. You should not be able to rotate the cable end by hand around the battery post.
If you don’t feel like you are making a good connection, just tighten it up with a wrench or pliers until it fits snug. Some battery bolts can strip out if over-tightened, so do not over-tighten.
#6. Bad battery cable.
Battery cables are what provide the power from the battery to the vehicle itself. Without power, getting to the vehicle is unusable, so battery cables are small but mighty.
#7. Damaged Ground Strap.
The connections of multiple components around the vehicle are connected to complete the circuits for the flow of electricity by a ground strap or ground wire. If the ground strap is damaged or removed, the battery may not charge.
You will most likely see a certain group of components in a specific area starting to act up if a ground strap is loose or corroded.
#8. Faulty Wires.
There are numerous wires involved in the electric charging system, so there is a possibility of any of them being broken or disconnected, thus can cause the battery warning light to be on.
Wires typically break around the connectors and not further up in the wire harness. Over time, the wires and several connectors can become stiff and brittle.
#9. Excessive Use of Accessory Items.
Accessory items off of the alternator belt, which is channeled through the battery charging system, in excessive amounts use electricity and sometimes leave the battery “hungry”.
Sometimes this scenario can happen with an aftermarket sound system that uses an amplifier that draws more power than the alternator can supply. Usually up-grading to a large, power sucking subwoofer has the potential of causing this scenario.
What to do if your battery light comes on?
So, you see the battery light? Don’t panic! Just breathe.
Right off the bat, you should also turn off all electronic accessories, except for the headlights. That means turning off AC, heating, the stereo, interior lights, heated seats/mirrors, phone chargers, and Bluetooth gadgets.
Now, be aware of overheating and/or loss of power steering. If you see either of these, you should stop the vehicle.
Now, to the problem of why this strange battery light came on.
Here is what you can do:
- Examine the battery. Look for any gunk or damage. It may have corrosion, which should be cleaned, but make sure that the clamps are tight.
- Examine the alternator. Make sure you have all electrical connections snug and not loose or missing.
- Check the serpentine belt. If you are seeing problems, such as overheating and/or loss of power steering, either of these is due to a worn serpentine belt. Look for significant cracks, breakage, or disappearance altogether!
- Check for fuse failures. While there are no blown fuses that relate directly to the care of the battery, it is worth seeing if there are any blown fuses you would like to replace.
- Test the battery: Now that you have done all the other steps, it is time to test the battery. Start the engine and observe the light. If the light turns off, you’re good. If it stays on, you probably have an alternator failure.
How Can I Troubleshoot Battery Issues by Myself?
If you’re comfortable with working on your car, you may be able to solve the problem yourself without paying someone else to do it.
You can likely handle it if the issue is simply corrosion or if you forgot to tighten a cable clamp. Grab your gloves, get your user manual, and let’s troubleshoot the battery problem together.
#1. Look for corrosion.
Batteries can sometimes get corrosion on the terminals during these hot summer months or when the car is located in warmer climates. To see if your battery has any corrosion, first, take off any protectors that may be covering your battery terminals.
You may notice a white or greenish substance around the terminals. That’s corrosion. Corrosion often happens and is a valid reason for any battery disruptions because these deposits mess with the flow of electricity between the battery and other components of your vehicle.
Please do not touch the corrosion with your bare hands because it can irritate your skin. If you are unsure how to clean it check out our guide. Moving on to the next troubleshooting question…
#2. Clean the battery terminals.
It is really easy and inexpensive to clean the terminals on your battery yourself. Just stop by the nearest store and purchase some battery cleaner, or use your own solution by mixing some baking soda and water. Remove the terminal covers and disconnect the battery cables.
Remember to first disconnect the negative (black) cable and then the positive (red) wire. Once you have disconnected the wires, apply your cleaning solution to the corrosion around the battery posts and wire ends. Then scrub and clean the battery posts and wire ends until you have no corrosion left.
Attach the battery cables by connecting the positive (red) wire first, and then the negative (black) wire.
#3. Tighten the cable clamps.
If it seems like your cable clamps are just loose, then this could be the reason you have an illuminated car battery light.
Don’t panic! Check your owner’s manual for any specifics, but usually, you will just need a standard wrench or socket wrench to tighten them.
What to do when your car battery light is still on?
You checked for corrosion and smoothed out loose battery cables, but the battery light is still on. Uh-oh! Something mechanical or electrical may be a problem, an alternator or voltage regulator issue, perhaps, or a hidden wiring problem.
Time to take the car to a local mechanic or repair facility. They will inspect the vehicle and conduct a voltage test. Then, they will provide some service recommendations based on what they find.