Why Is My Car’s Battery Light Coming on When Accelerating?

Typically, your car battery light should only come on for a few seconds and then go off once you start the engine. However, in a case where the red light comes on when you accelerate your car, it may be an indicator of an underlying issue.  

This red light functions as a signal for the status of the car battery. It tells you if the battery has a low charge left or if the battery has a charging problem. 

battery light on in car

The car battery light may come on while accelerating for reasons such as; the battery suddenly charging at a higher rate than normal, a faulty alternator, a damaged battery, and a couple of other reasons you will learn in this article. 

If your car’s battery light turns on during acceleration, the reasons may include;

  • Worn-out drive belt: your car’s drive belt slipping at high RPMs (Revolutions per minute) due to slacking, wear and tear, or looseness may be a reason for the lights coming on. If the drive belt does not hold on to the pulley to drive the alternator, it could also be the reason as the battery won’t charge normally. Belt slip-ups also cause the alternator not to generate power fast enough. 
  • Poor battery cable connections:  the cables may have been loosely connected to the terminal, impeding the flow of current. This can cause the battery to charge slowly or not charge at all. Also, corrosion around the terminals can affect contact between the battery cable and the terminal. 
  • Bad battery: a faulty or damaged car battery is another common reason. When the battery is defective, it can lead to a fast drain of power while driving. 
  • Faulty alternator: your alternator can be diagnosed using a multimeter. The voltage regulator, which is supposed to keep the output at a safe limit, can also be the reason for the alternator’s malfunction. The normal alternator voltage should be between 13.6 and 14.6 volts. Anything less than 12v can set off the battery lights. 
  • Faulty wiring: Cars involve a lot of wiring; hence broken or faulty connections might make the battery warning light come on. 
  • Heavy electrical load: using too many accessories while operating the car can cause a shortage in the current supply to charge the battery. Using the electrical accessories excessively can zap out too much electricity, leaving the battery deficient in charge. An example is using a sound system that uses an amplifier taking more energy than the alternator can handle 
  • Bad Ground strap: A ground wire helps electricity flow as it should, completing the circuit of different electrical components of your car. A detached or damaged ground strap would prevent the battery from charging, and some parts will begin to act up also. 
  • Faulty dash cluster: Although this is an uncommon cause, it is not impossible. A faulty dash cluster also comes with other faults like wrong odometer readings and lights coming on when they should not. You can get your dash cluster bench tested at the mechanics to confirm. 
  • Worn-out pulleys: Some alternators have a pulley specially designed to spin in one direction. This minimizes damage to the alternator but can also go sideways when there is a fault. To check the pulley, remove the drive belt and manually turn the pulley. If it does not spin freely in the direction it usually moves, then you should have the pulley replaced.  

Now that you have learned possible reasons why the battery warning light comes on acceleration, one thing to notice is how much it is linked to the battery and its charging. 

What To Do If Your Car Battery Light Comes on When You Accelerate 

Here are possible checks and fixes you can do if your car warning light turns on when you speed up.

  • Confirm the occurrence: Check if the light coming on was just a one-time thing or if it happens consistently by slowing down your car first and then accelerating again. Observe what happens in these two processes. Does the light go off when you slow down? And does it come on again when you speed up? Doing this helps you identify if the problem is a recurring issue or not. 
  • Save the battery charge: Avoid turning the car engine on and off, as more power is used when you start your car. 
  • Check the battery and charging system: inspect the battery for leaks, swollen casing, corrosion, weird odor or faults, and cable connection. Check if the cables are firmly tightened to the terminal and if the battery is holding charge normally. A fully charged battery should read 12.7 volts. Anything below this shows a low charge. If you do charge the battery, but it does not hold a charge, it is best to replace it with a good battery. Also, if the cable connection is loose, use a wrench or pliers to tighten it. 
  • Check for corrosion: Rusting terminal causes a buildup of sulfate crystals around the terminal, which affects contact and free flow of current. This is easy to fix using battery terminal cleaning spray or a mixture of baking soda and water in paste form. Apply any of this mixture to the corroded area, and scrub with a wire brush till clean, after which you rinse and dry off using a clean rag. To prevent future sulfate buildup around the terminals, coat the now dry terminal with grease or petroleum jelly. 
  • Check the alternator output voltage: Use a multimeter to check the output voltage while the car is running idle. You might need to replace the alternator if the reading is above or below 14.5volts to 14.7 volts. 
  • Change the drive belt if worn out: if it has been in use for a long time, or it is beginning to show signs of slacking, wear and tear or cracks, then it is best to replace it with a new one. 

Should I Keep Driving While the Battery Light Is On? 

As a newbie, or if it’s your first time encountering this issue, you may be confused as to whether you should keep driving or not. It is not advisable to keep driving in this state because there is a chance your car will get stuck on the way due to battery failure. If you cannot stop immediately, plan to stop at the nearest possible place, preferably a mechanic, to help you check the problem and restore the battery charge system. 

Also, once you notice this light coming on in motion while looking for the best place to stop, turn off other car accessories or attachments that use up electrical power, such as the stereo, charging phones, massage chai, and the likes. This will help to save power until you get it to the mechanic. 

Tips For Improving Your Car Battery Span  

Since most of the issues related to the light coming on have to do with the battery, here are some things you can do to make your battery last for longer; 

  • Keep your battery securely in place: A loosely placed battery could vibrate out of place, causing a short circuit and internal damage. This is common in bumpy terrains that cause your car to shake. 
  • Turn off the lights when you turn off the engine or get down from your car: always remember to switch off the lights. If you must, keep a sticky note on your dashboard to remind yourself. 
  • Test your battery regularly: Test your car battery’s voltage level regularly using a multimeter or car battery tester. This can help you keep track of your battery’s health and prevent further damage from happening. 
  • Keep electrical components or devices off during idling: to save battery power, turn off appliances like stereo, air conditioning, and the like. Also, avoid idling for long periods as this can wear down the battery. 
  • Avoid unnecessary short rides: short rides do not let your car battery charge fully. If you must ride, try to do it for an extended period to let the battery charge to capacity. If you hardly use your car, you can get a portable charger to help jump-start your car when the need arises.
  • Control corrosion: treat and prevent corrosion by scrubbing off the white residue with a terminal cleaning spray or baking soda plus water mix and a wire brush, rinse and let dry. Apply grease or petroleum jelly around the terminals to prevent further rusting. 


How long does a car battery last? 

Your car’s usage pattern also contributes to the lifespan of your battery. A new battery should serve you for up to five years, provided you maintain it properly, and it is a good brand. Some may even go a few years more than that.  

When should I replace the alternator? 

The alternator’s function is to charge the battery while your car is running; however, a faulty alternator leads to a dead battery after some time. Your alternator only needs a replacement if it stops working. 

Final Thoughts

Your car battery is an important component of your car that should be treated with care and priority. Always choose a durable and good battery for your car, and do not ignore any warning signs it gives. 

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