9 Causes of a Car Battery Light On While Driving
A battery warning light while driving is cause for alarm as it likely means your charging system has failed. Ignoring this red flag can leave you stranded with a dead battery.
Learn the most common reasons battery lights illuminate and what you should do if the battery light comes on while driving.
How Conventional Vehicle Batteries Work
Batteries are used to store energy to keep the vehicle and its power accessories working. Chemical energy stored in the battery is how the vehicle can be started initially and then as it runs, the battery is recharged.
Recharging happens when the crankshaft pulley turns the alternator belt (also known as serpentine belt or accessory belt) which spins a rotor inside the alternator (which is sometimes referred to as a generator).
The alternator takes kinetic energy from the rotating pulley and converts some of this energy into AC power, which is then converted into DC current and stored in the battery. This energy is then used to power things such as headlights, power windows, heated seats, radio, air conditioner, DVD players, and cell phone chargers.
Note: Older vehicles may use a dynamo (also called a DC generator) instead of an alternator.
The voltage regulator maintains the desired voltage while charging the battery. It is often a component of the engine control unit (ECU).
The current (made of electrons) flows from one post of the battery, through the accessories, then into the other battery post. Various wires around the engine bay called ground straps connect parts of the wiring harness to the chassis, which help complete different circuits.
Top Reasons a Battery Light Comes On
Every time the vehicle starts up, the battery warning light should briefly turn on, then back off after a few seconds. This is a system test that indicates the battery light on the dash, along with any monitored components of the charging system, are working as expected.
The warning light for the battery will stay on if a fault is detected in the charging system. If this occurs, there are a number of potential causes to check out when troubleshooting.
Safety is important whenever working with electrical systems, so check your owner’s manual for general tips. It’s a good idea to wear gloves or goggles to protect your eyes if battery acid splashes, and rubber gloves to protect you from shock. Disconnect the battery before cleaning or closely examining it.
If the battery is having trouble charging, you should notice other symptoms such as dim headlights, clock running slow, or things such as the air conditioner or radio not working.
#1 – Bad Battery
Normal 12 volt batteries have a 3 to 5 year lifespan. Some manufacturers tout a longer lifespan, but the batteries should not be expected to last that long.
These conventional batteries each have a lead dioxide plate and lead plate submerged in a sulfuric acid electrolyte solution in each of the six cells. With age, the cells or plates can break and the electrolyte solution can start leaking out of the battery. If this happens then the battery needs to be replaced.
Bad wiring or bad grounds can also cause the battery to not take or hold a charge.
#2 – Bad Alternator
It’s relatively easy to check the function of the alternator with a multimeter. The voltage should be between 13.6 volts and 14.6 volts. If the voltage is less than 12 volts, the battery light is triggered and you’ll likely need to replace the alternator.
The voltage regulator, the component that limits the output to a safe limit of 14.5 volts, can also be the culprit if it isn’t working as it should.
See Also: Difference Between a Dead Battery vs Bad Alternator
#3 – Bad Alternator Belt
An alternator belt is crucial since it connects the alternator, engine, and accessories together. Belts can crack with age or even completely break. They can also be misaligned, too tight, or too loose.
If a bad alternator belt is the cause of the battery warning light, it may also cause squealing from the hood when the vehicle is running.
#4 – Corroded Battery Terminals
The positive and negative battery terminals are channels for the electricity, so it’s important not to increase the resistance by covering them with other substances that are poor conductors. Corroded electrical components are poor conductors. This is often a source of bad connections in an otherwise healthy system.
Corrosion is the white, blue, or green product of a reaction that happens with normal use and is accelerated by persistent heat, so hot climates are associated with more corrosion.
It’s an acidic substance and will eat away a vehicle’s paint and irritate your skin, so use caution. Typical rust has a reddish tint and may also affect the electrical components’ conductivity.
If you notice corrosion on your battery terminals, don the appropriate safety gear and clean the terminals with a stiff-bristled brush and a solution of 1 tablespoon baking soda dissolved in 1 cup water. This solution is alkaline so it will neutralize the acid in the corrosion.
Battery terminal cleaners are special brushes that are specifically designed to clean battery posts and the inside of terminals. They are cheap and may make the job a bit easier.
#5 – Loose Battery Cable
The battery cables should fit snugly 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 there doesn’t seem to be a good connection, tighten it with a wrench or pliers so that it fits snugly. Some battery bolts can strip out if over tightened, so be sure not to overdo it.
#6 – Bad Battery Cable
Battery cables deliver the power from the battery to the vehicle itself. If the power can’t get to the vehicle, it’s unusable, so these cables are small but mighty.
#7 – Bad Ground Strap
A ground strap, or ground wire, completes the circuits of different components around the vehicle so electricity can flow as it should. If the ground strap is damaged or detached, the battery may not be able to charge.
More than likely, you will notice a specific subset of components in a localized area start to act up if a ground strap is loose or corroded.
#8 – Faulty Wiring
There are a lot of wires involved in the electric charging system so if any of these are broken or disconnected then the battery warning light may come on.
Wires typically break around the connectors rather than further up the wiring harness. The wires and connectors may become stiff and brittle with age.
See Also: 6 Symptoms of a Blown Alternator Fuse
#9 – Too Many Accessories in Use
Since the vehicle’s accessories run off of the alternator belt, which is also how the battery is charged, using them in excess can siphon too much electricity, leaving the battery “hungry”.
This can sometimes occur with an aftermarket sound system that uses an amplifier that consumes more power than the alternator can handle. Usually this is the case when adding a large, power-hungry subwoofer.
What To Do If the Battery Warning Light is On
If you are driving and the battery warning light comes on, know that you probably don’t have much time left of driving before your vehicle dies. Try to get home or to a mechanic as soon as possible.
To get the most out of the juice left in the battery, reduce the accessory load to the bare essentials – turn off the HVAC system, don’t use power windows, take your phone off of the charger, and sing to yourself instead of using the radio (you may want to keep the windows rolled up).
Whatever you do, don’t turn off the engine until you’ve reached your destination! The starter motor takes a lot of electricity and if there isn’t enough charge in the battery then the vehicle won’t start.
Keep an eye on your temperature gauge, as overheating can be an associated issue with charging problems.
He’s known for his attention to detail and problem-solving skills and enjoys coming up with out-of-the box solutions when the situation requires it.
When he's not troubleshooting customers' cars, you'll most likely find him working on his current project ('96 Bronco) or cooking Italian food for his family.
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Can corrosion eat out all the battery cables up to the alternator? My civic 2001 has serious corrosion issues and it looks like all the wiring is eaten out. The wires are rotten if I can say
I don’t know, I suppose if the rust were really bad it would be possible. If the corrosion is that bad you’re probably going to have to replace those cables.
My 2008 accord lx has a weird charging problem that no one but me seems to have. I’ve had the battery light come on for a second or two then turn off but only seldomly. I recently got a cig lighter splitter with a volt reader and noticed when I’m driving above 10-15mph my volts drop from 14+ volta to 12.6. If I rev to about 3k rpm or throw it in neutral it immediately goes back to charging at 14+ volts, put it back in drive it drops again or if i go below 3k rpm as well. In park its fine when stopped in drive its fine until I get up to roughly 15mph then charging stops and volts go to 12.6v and if I stop it takes a few seconds maybe 10 secs but will go back to ~14.2v. What would cause that to happen. Battery is good, alternator seems to be good as well and I don’t see any wiring or grounding problems but have not done any testing on the wiring.
Check that your battery terminals are clean and tight. It’s possible that as the vehicle moves, the vibration and shifting weight could temporarily reduce the quality of the contacts with the battery.
Ok I think I figured out what’s going on and it’s suppose to do that. Hondas have a dual charging system that when in drive going between 10-45mph or at idle in drive, ac switch off, coolant above 165f, rpm below 3000, electrical load less than 15 amps but can vary with vehicle, and air intake temp above 68f, it will go into low output mode which puts it at 12.4-12.9 volts and anything outside those parameters it goes back to high output mode. So that’s good, but I do get once in a long time have my charging system light come on for a couple seconds to just a brief flash so I may still have a slight electrical problem which could be my sound system and I will soon install a 2 farad capacitor for my sub which is 500watt rms and that when it’s banging dims the lights and found that could damage or at least shorten the battery life and could be causing electrical issues and may be causing the charging system light to come on briefly. That took me forever to find this info, and maybe help some people that don’t know about it.
I’m using a Mecerdez Benz C240 2005, my battery alternator light has been showing and I’ve change the alternator for about four, and I even upgraded it to a higher voltage and I’ve also change the belt & bought a new battery & it’s still showing. What could’ve been the cause & it’s solution?
Could be a bad connection to the alternator that is not allowing the battery to charge properly. It’s probably best to do a test with a multimeter (in the hands of a qualified technician) to diagnose the electrical issue.
Your alternator charging or not if charging then then check alternator wiring
I have a Volvo S80 d5 2005 started car drove down street and message saying electrical current high and red triangle lit up and battery light on checked battery holding charge ok can leave it a week and it starts no bother but has the above back on alternator lowest is 13.8 volts up to just over 14 volts checked all earths plus harness wires etc found nothing so decided check brushs they were approx 5 mm which is still acceptable but changed with new Bosch voltage regulator all readings the same and same lights on again any ideas would be a help
I don’t know. I would check the factory service manual for troubleshooting and diagnostics related to that light. The manual will probably have a list of possible next steps to try.
Some good information here but it’s not in the same way as I am having problems with my Volvo
What problems have you been experiencing?
am using Toyota Camry and battery light always shows on my dashboard, I have called rewire man and worked on my alternator. The light stopped latter came up again. I have to the rewire again and said i have to change my alternator.
please help.
What work was done on the alternator? Is there a specific question you have about the battery light?
All of my questions on my mind were answered. Thank you so much!
Happy we could help!
My polo 2007 ,when I go to a stop or at a robot,car switches off and dash battery comes on,have to restart car again pls help
You’ll have to do some diagnostics to figure out what the problem is. Are there any codes? Have you tested the battery and alternator?
Hi,my the battery light goes on on my car.checking its showing that its charging.this was checked by an auto electrician.so what could be the problem
Have you also tested the alternator?
Can a bad negative wire cause a battery light to come on..has a good cahrge on the battery and alternator
The negative wire is almost always the ground wire. Yes, a bad ground at the battery could cause the battery light to come on.
What leads you to believe the negative wire is bad?
2016 Nissan Rogue SV. Stalling at traffic lights, won’t accelerate, idles at around 1800 rpm. Barely made it home. Went back out to troubleshoot. Engine would turn over than die. Kept foot on the gas and started engine again. Revved up to 7000 rpm. Now it fires right up and runs just fine, idles at 800 rpm but battery light is on. Any thoughts?
My first thought was the idle air control valve (IAC), but that doesn’t explain the battery light. I would have the battery tested and check for vacuum leaks. Test the alternator as well, and make sure the serpentine belt tension is correct.
I have a Suzuki sx4 S-Cross. The battery light comes on while the vehicle is moving. When you turn the light off and on again, it goes out again. I already changed the alternator and battery. Always accused that the battery is being charged, can a cable fail intermittently? Could it be an escape to ground?
Check the alternator pulley and serpentine belt tension. It wouldn’t hurt to check the battery terminals for corrosion and make sure the cables are tight.
My polo warning light battery comes out when I turn on air cond. Why?
I’m not sure. It could be an issue with the alternator that causes the additional power draw of the air conditioning to drop the voltage lower than expected.
I would have both the battery and the alternator tested and go from there based on those results.
About a month ago we had a cold snap. I live in southern AZ. My mechanic ended up changing a lot of alternators when this happened. My battery light comes on, off and on. It can be when I first start it up, or even while I am driving. I had everything checked out by my mechanic and an auto parts store. I opted to replace the battery since I didn’t know for sure how old it was. It was fine for awhile, and now it comes on intermittently. Both places say the alternator is good. I hate to start replacing parts to diagnose on my own. I can drive well over a hundred miles, upwards of 300 on a trip and then back home again. Lights do not dim when battery light comes on. Turning everything off does not affect the light at all. When I had the auto parts store hook up and check, they said the battery wasn’t charging completely. Even though they said the alternator was fine.
That’s a tough one. I would check all the grounds to make sure they are clean and tight. Since you’re in Arizona, I am assuming rust isn’t too big an issue?
Perhaps the battery has a bad ground and therefore isn’t charging very well. Clean the battery terminals as well.
Hi I have changed alternator battery and belt and checked groundings on my son’s 2010 ford focus. But when driving the battery light will come on for a couple of minutes then go off again, it does this intermittently but it does get better as the car warms up. We don’t know what else to try so I’m hoping that someone else has solved a similar problem. Thanks
You will probably have to do some additional electrical diagnostic work to find the root of the problem.
Are you handy with a multimeter? If you can get your hands on a factory service manual (or even a repair manual such as Haynes or Chilton), they should have some troubleshooting steps you can take when the battery light comes on.
My battery light comes on, but a few seconds later it goes off. This will happen several times during the same trip.
Could it be that the battery light itself has a short?
A friend checked my battery – it holds a charge. Alternator works. He cleaned the battery terminals.
Yet the same problem – on the same trip a battery light will go off and on. It’s NOT a steady on. It will be on for a minute, then go off for a minute.
I’m not sure. It could be a bad connection between the alternator and the battery. Perhaps the alternator is working intermittently. I think further testing will be needed to know the exact cause.
I had the same problem and eventually the light stayed on until my car almost left me and my 1 year old stranded.
Hi,
I have a Toyota RAV 4 2010. Last week my car started making whistling noise, the battery light was flickering while driving and steering got locked. With some difficulty i parked on the side and took the car by Recovery van to a mechanic. As expected the issue was on Alternator. They changed some bearings inside the alternator and the car was fine for couple of days. After two days again battery light was on. Once again i took it to the same mechanic. He fixed the bearings again and for two days it was okay.
Today i have encountered the same issue. No noise. But battery light was flickering while driving every 30 seconds. Steering got locked and unlocked couple of times. It was scary but somehow i drove to safety. I spoke to the mechanic. He said he has checked it twice and there is no electric issue in the car. Can you please share your opinion. Thanks
I would not drive the vehicle any more until you get that issue sorted out by a qualified technician who can see the vehicle in person. Locked steering is very dangerous and has a high risk of causing an accident.
If I had to guess, the alternator locking up is causing issues with the power steering pump. It’s the only way I can think those two systems would be related. If the alternator bearings failed, I would examine the other pulleys driven by the accessory belt to make sure they are functioning correctly. Perhaps the alternator belt tension is being set too tight and is causing premature bearing failure.
I would be worried about the water pump pulley in particular if your water pump is driven by the same belt as the alternator (I’m pretty sure your RAV4 is designed this way). One of the most common causes of water pump failure is incorrect belt tension.
My Toyota Previa 2006 has a newly replaced battery & alternator(reconditioned/2nd hand)But the dashboard battery lights on. I run the engine for an hour in the parking lot still the dashboard battery lights on… What would the fault this time?
It’s impossible to say without some testing. See if there are any codes to scan to give you a starting point. Next, I would do some searching on Google to see if there’s a common issue specific to that model.
Sometimes remanufactured parts come faulty out of the box. I wouldn’t assume the alternator is good, and would have both the alternator and the battery tested just to make sure.
I replaced a new battery 5 months ago on Peugeot partner 2011 last night the battery sign came on dashboard and while I was driving down hill switched off the car but didn’t start with ignition then I had to start it on 3rd gear and it was fine after few minutes the battery sign came back on dashboard then while driving it the lights started to fade and all lost all lights and the car stalled, I checked the the battery for a green light it was ok then checked all wires and fuses they were all ok as well I tried to turn on the car but didn’t even start. So these signs looks like alternator or battery? Also the car starts by pushing but when you take of the car battery Negative or Positive the engine stops straight away. I’m thinking to change the alternator to see if the goes back to normal.
You should be able to test the alternator before you swap it out. Might save you some money if it ends up not being the issue.
The battery light is coming on but my car is running OK. Any ideas?
There is a battery charging or voltage problem. I would have the battery and the alternator tested so you aren’t left stranded when you go to start the car one day.
i had the same issue,my battery light comes on and goes off while driving.i just replaced my alternator and battery.i have 2008 honda accord v6.
Hey elaud you ever fix this issue
Start car. Remove one of the cables from the battery while it’s running (Be careful not to short your wrench out between + and – ! ) If it keeps running, alternator is likely ok. Also check that your belt is tight and not slipping.
I conect the wrong wire with new battery and the alternater produce smoke and smell
And the battery sign show after starting the car
Check that you have no blown fuses, and have the battery and alternator tested. You can do this at a local parts store and it shouldn’t cost anything. It’s easy to cause damage by wiring the battery backwards or jump starting the car incorrectly.
My battery light came on when away on holiday, i had a local garage check the battery was fine and the alternator was fine but its still on i noticed i went through a large amount of water on the road and the light went out for about 30 seconds but came back on again. Its doing my head in any help would be appreciated before i book into an auto electrician.
I recently replaced my alternator and since replacement I have had a battery and stop light flash on and back off again within a second only comes on every few mins doesn’t effect power or anything checked all fuses cables etc but everything seems fine any idea
My interior lights go on and off while I’m driving
I’ve had check charging system light for a couple of years
What needs to be checked
Possible voltage regulator.
My light goes on and off but alt tests good (13.5-14,5),new battery ,cables clean ,starts even if you keep lt parked .2wks stays steady with lights and heater on,voltage never drops below 12.2 battery .starts everytime ???? HELP ……2007 ford focus ses
I’m having the same issue. A 2005 Ford Focus. Did you figure out the issue ?
2002 Ford focus same problem
The first generation Ford Focus seems to have an issue with the fusible link and parts of the wiring harness near the alternator going bad, causing a battery light when the alternator and battery are both good.
To test if this is your issue, you’ll need a multimeter. Do a quick search with your year and exact issue and you’ll find a couple things you can try that are fairly well documented on forums and YouTube.
My battery light came on while i was driving home from work which is about 30 miles one way and then when i parked the car and turn off the engine for a few mins then I turned the car back on the light went away. what can cause this? also during that time my check engine light went on and the code said it was the thermo went out but then that light went off to after i turned the car off then back on.
It may be that the altenator was not an OEM replacement for the old one. If that was the case, then the new alternator may not be a good replacement. You may want to try and start the car and then disconnect one of the battery terminals. You the engine stall upon disconnection, then the alternator is the culprit. You may also get a multimeter and test how much volt the alternator is chunning out (it should be atleast 13v). If the voltage generated by the alternator is below this voltage, once again you have a faulty alternator.
My power steering goes off and then back on while driving
How did you resolve this issue?
Don’t know if he did, but sounds like a pump problem to me.
So what if your driving down the road and your head lights dem in and out and at the same time you lose power you can and feel the lost of power to your motor
Battery light on off and on???
Check/tighten all connections and grounds on the alternator and battery.
Bring it to a mechanic to check the alternator for charging the battery. You may also check the voltage regulator
I have a question please….
My cars battery light came on after a new starter was installed, I bought a brand new battery the month prior. My mechanic thought it was the alternator!! He changed the alternator and battery, and checked all of the belts, fuses etc and nothing seems to make the light go off. I’m confused does anyone know what else it could be that causes the battery light to come on??? Is it the cars computer?
Hi
I don’t have the answer but I’m really Im interested if you managed to solve the problem?
I’m sure you fixed this by now but it sounds like you have a cable problem.
It is possible that when the mechanic installed your new alternator he didn’t properly attach the ground.
Also wondering if you were able to fix the battery light problem.
It could be your brake light switch which is underneath the brake pedal
I took my Ford Flex SUV to a local dealership because my battery light came on. Since my vehicle is 11 years old, I figured the alternator probably needed replaced. The mechanics said my alternator is fine and the battery light coming on is caused by damaged wiring in my wiring harness (they suspect acid from battery damaged the wiring). Well they ONLY want $829 to fix it so I’m holding off for a bit until I can shop around for a better price.
Thought I’d at least give you the reason my battery light is coming on since it’s a mystery with your car. Just something to check out possibly.