Battery and Brake Light On (Causes and Fixes)

Battery and Brake Light On

Did you notice that your battery and brake lights come on simultaneously? And the worst part is that you don't know the cause or how to fix the situation. This mostly happens after replacing the alternator or just randomly when you are driving.

There are several reasons why your battery and brake light comes on randomly. There are chances that your brake fluid is low or your alternator or battery has some problems. They could be going bad, or you just have some loose connections.

If your car has an anti-lock braking system, then you might have some problems, like increased power consumption, issues with the voltage regulator, or loose connections.

Here's a detailed guide on why your battery and brake light is on and what you should do when this happens.

Can a Bad Battery Cause the Brake Light To Come On?

Yes. Bad batteries can cause brake lights to come on. Most times, when your battery is dead or bad, you'll have many lights on your dashboard. This happens because enough power isn't supplied to those systems; unfortunately, the brake system is among those systems.

Sometimes, the battery might not be that bad, but the connections are. If the battery connection doesn't allow the alternator to get enough charge power to the battery, then the battery and brake light will come up.

Why Would Battery and Brake Light Come on at the Same Time?

There are a lot of reasons why your battery and brake light are coming on at the same time. Understanding why this is happening is your first step to solving the problem.

1. Bad Alternator

Bad alternators are one of the most common reasons why the brake light and battery come on simultaneously. If you take your car to a mechanic shop to complain about your battery and brake light coming on, there's always a 95% chance that you have a faulty alternator.

Either the alternator doesn't get enough power, or it's finding it difficult to sustain the battery at full charge.

If the alternator fails to charge the battery properly while the engine is running, the battery will run out of power. That’s because the battery powers all electrical components of the car, and the alternator charges it.

And when this happens, the warning lights will be triggered for systems that aren't getting enough power from the power. The brake system might be one of the systems lacking a power supply.

When this happens, while the battery light comes on because the battery is drained or not getting enough power from the alternator, the brake light also comes on because it isn't getting enough power. If the situation lingers unsolved, you'll experience poor engine performance and stalling, and eventually, the engine will not start.

2. Bad Battery Connection

Sometimes, you might not necessarily have a bad alternator. Your battery connection might just be faulty. This can happen if the battery terminals are dirty or not fitted properly or if the connections are loose, weak, or damaged.

The fault ranges from bad battery cables, corroded lines, or wiring. When any of this happens, enough power wouldn't be delivered to the vehicle. This can trigger the brake lights if the brakes aren't getting enough power.

The battery warning light will also come on because there's enough power that is not being used by the vehicle.

3. Bad Voltage Regulator

A bad or failing voltage regulator remains one of the root causes of your battery and brake warning light coming on simultaneously.

The work of a voltage regulator in a car is to ensure that there is a constant power supply across the circuit of your vehicle. This ensures that the voltage transferred through your car's circuit is the same.

When you have a failing voltage regulator, the voltage regulator will overload or underload your car's alternator, developing several issues in your car systems.

This will send the wrong voltage across the different systems of your car. If the brake system is affected, the brake light will come on, as will the battery light.

It is important to mention that an overload on your alternator can seriously damage your car, more than just turning on your brake light, so you must fix it urgently.

4. Malfunctioning Braking System (ABS)

Sometimes your battery and brake light will come on if your braking system is developing some issues.

This doesn't occur regularly, but we can't ignore that it can happen. This can happen if your brake lines are bad or if there's an electrical fault with the brake system. As long as the fault is electrical, your battery light will come on, as will the brake light.

5. Low Brake Fluid Level

One of the most common reasons brake and battery lights come on simultaneously is low brake fluid. The first time I had my brake and battery light come on simultaneously, I realized that my brake fluid was right at the minimum line.

The brake fluid helps in delivering the required pressure to stop your car. There might not be a logical way to explain the connection between the battery and the brake light in terms of low fluid level, but it always happens. So, check your brake fluid level next time you notice both lights come on.

6. Sensor Malfunction

Everything in your car might be working fine, and the only problem is that you have bad sensors. You might necessarily have corroded battery cables or a bad voltage regulator, not even a malfunctioning brake system, just that your sensors are failing.

They end up miscalculating, sending signals that your brake fluid levels are low, causing your brake light to come on.

Is It Safe To Drive With the Battery and Brake Lights On?

It is not safe to drive your car with any arising problems. You should park or take your vehicle to a mechanic for inspection immediately after you notice that your battery and brake lights are coming on.

An inspection will help determine if you have a dead battery, bad alternator, poor connection, or voltage regulator. Some causes of the brake and battery light coming on might go as far as damaging your car or keeping you stranded in the middle of the road.

Battery and Brake Light Coming On: A Quick Fix

The solution for the battery and brake light coming on depends on the exact cause of the problem. If you can trace the cause of the problem, you're halfway close to solving it.

Here are nine things that you should do when your battery and brake lights come on at the same time:

  1. Top up your brake fluid.
  2. Clean battery terminals.
  3. Check your battery's ground.
  4. Tighten cable clamps and look out for loose connections.
  5. Look out for corrosion and clean any build-up on the terminals.
  6. Replace the alternator if damaged.
  7. Change the battery if necessary.
  8. Inspect your brake system.
  9. Inform a professional.


Battery and brake light coming on is a common issue amongst drivers. It doesn't mean that the end of your car is near or severe damage has occurred. You just need to trace the fault and address the problem.

There are chances that you can fix some of the problems yourself, but if you are unsure of what to do, you should seek a professional's help.

Frequently Asked Questions

Why does my brake and battery light come on when I accelerate?

There are many reasons why your brake and battery light will come on when you accelerate. It's probably because you have loose connections, a dead or dying battery, corrosion on the battery terminals, or the voltage regulator isn't working well.

Whichever case it may be, you should take your car to a mechanic for inspection to decide the exact cause of the warning lights and fix them immediately.

Can a bad alternator cause the brake light to come on?

Yes. A bad alternator can cause the brake light to come on. This is because the alternator handles the charging of your battery, as the battery delivers power to the electrical components of your vehicle.

So, if the alternator isn't working properly, voltage delivery will be low, affecting different vehicle systems, including the brake system. If the brake systems are affected, the brake lights will come on.

Why is my battery and brake light on after changing the alternator?

Your brake and battery lights might still be coming on after you've changed the faulty alternators. This can happen because the damage doesn't stop with the alternators. Bad alternators can damage the batteries, so you need to find a way to address your battery condition.