If the battery light suddenly turns on while driving, you’ll want to know how long you can continue.
Some drivers might think driving with a warning light is unsafe and would park their cars immediately. But you can usually continue driving and have some time to return home, get to an auto electrician, or park somewhere safely. How long you can drive in this condition depends on the actual cause.
If you only left the headlights on by mistake, you can probably continue driving indefinitely, and the alternator will recharge the battery in about 30 to 60 minutes. Otherwise, if there’s a problem somewhere in the alternator-battery charging system, you can usually continue driving safely for around the same time, i.e., at least half an hour or up to one hour before the car stalls.
The vital engine functions will use the battery’s reserved power, but turning off unnecessary accessories is recommended. Ultimately, however, you must identify the underlying cause and do what is necessary to deal with the problem accordingly.
The solution might be as simple as securing the battery’s connections, cleaning off corrosion on its terminals or the battery sensor, or replacing the fuse. Or it may require replacing the battery, a damaged cable, or fixing the alternator. Once addressed, the battery light should go off, and you can enjoy driving as normal.
I also cover common causes of the battery light indicator in detail, what enables you to continue driving and tell you what you can do yourself when faced with a battery light on while driving below.
The Battery Light
A car’s battery light is normally located on its dashboard, in the shape of a battery outline in red. The red color usually signifies that something is wrong. Some or other cause will have triggered the light to come on.
Causes of the Battery Light Indicator
The battery light indicator on the dashboard signals a problem with the battery’s charge or charging system or that the voltage is low.
Leaving the Headlights On
One cause might be as simple as having left the headlights on for a long period.
If this is what happened, you probably don’t need to worry so much. The battery, alternator, and the rest of the charging system might be fine. The battery light will only be on temporarily until you keep driving and the battery gets charged more.
Insufficient Charge
Whether or not you left the headlights on, the battery light is a warning that the voltage level is currently insufficient to charge the battery.
It’s the manufacturer’s way of alerting you to a developing problem that could limit your remaining time to drive unless the situation improves. The seriousness depends on the actual cause and how long it will remain this way.
Weak or Failing Battery
A weak or failing battery will not be able to hold a charge long enough to drive the car without the battery light coming on.
Car batteries have a limited lifecycle, about 3 to 5 years if it’s a lead-acid battery. So if it’s that old, the age might be the cause. You can also confirm the battery is too old if you notice one or more of the following frequently:
- Dim headlights and car accessories are not operating normally.
- The engine takes too long to start, backfires, or doesn’t start easily.
- The battery has a constantly low water level or is swollen.
- You have to jumpstart often.
Some Other Problem
If the light persists, it confirms that the alternator isn’t generating sufficient electricity, if at all, or it’s trying to, but something else is the problem.
It’s not necessarily due to a weak or damaged battery, although that might be true. It could also be due, for instance, to a broken alternator belt or a failed alternator.
So the cause of the battery light indicator is within this electrical system in the car, involving the alternator, the battery, and the connections between them:
Specific Causes
Specifically, the most likely causes are:
- Leaving the headlights on too long (while parked)
- Too many appliances using the battery at the same time
- A blown fuse
- A dirty battery sensor
- A loose battery cable
- A damaged battery cable
- Too much corrosion on the battery’s terminals
- A fault in the car’s wiring that connects the alternator and battery
- A battery too weak or old to hold a charge
- Damaged cells or plates in the battery
- A leaking battery (smell of sulfur)
- A slack or broken alternator belt
- A problem with the alternator or voltage regulator
A Faulty Alternator
A faulty alternator causing the battery light to come on would be more difficult to fix.
You can tell if it’s the alternator at fault by noticing one or more of the following symptoms:
- Dim, flickering, or overly bright headlights
- Abnormal function of accessories
- Difficulty in starting the engine and frequent stalling
- A smell of burning electrical wires or rubber
- A whining or growling noise from the engine bay
External Causes
The cause of a battery light coming on is not necessarily internal.
Internal causes are most common, but temperature can also be a cause. That’s because ambient temperature affects a battery’s ability to store charge [Wei Liew, 2023]. This ability drops when the temperature falls below 77°F (25°C).
Therefore, you must drive longer if the battery light comes on during cold weather.
Things that Enable You to Continue Driving
The reason you’re able to continue driving even with the battery light on is that the battery may still have some charge.
The engine can still run with a broken alternator belt or a faulty alternator, but only as long as the car has already started and there is some charge in the battery.
The only difference will be that the battery will not get charged, so you will only have until the remaining charge is depleted.
Driving Beyond the Limit
If you continue driving beyond the limit of 30 to 60 minutes, the car will eventually stall because it will run out of electrical power.
What to Do with a Battery Light Problem
You can only drive so far with a battery light and must address the cause soon.
Continue Driving
You only need to continue driving if you left the headlights on by mistake.
If everything else is operating normally, the alternator will charge the battery in about the same time, i.e., 30 to 60 minutes, to get fully charged again. The light should go off sooner when the voltage exceeds the minimum threshold of 12 volts. Only if this doesn’t happen and the light stays on will you need to do something additional.
Regardless of the cause, turn off all unnecessary accessories as well. If you don’t, they will burden the limited battery charge extra.
Take Further Action
It’s important that you deal with the problem because you won’t be able to continue driving beyond what the existing charge allows, i.e., around 30 to 60 minutes.
You don’t want to be left stranded somewhere with a stalled car. Consider the remaining charge enough to get back home, go to an auto store, or park in a safe location. If the light remains on, and you cannot identify the cause, it’s best to take the car to an auto-electrician for a proper diagnosis.
If you want to deal with the problem yourself, here are some checks you can do.
Check the Fuse
A blown fuse would cause the battery light to come on. Replace it if it’s blown.
Check the Sensor
Ensure the battery sensor is clean.
You’ll normally find it on the battery’s negative terminal, but it could also be on the positive terminal. Replace it if it’s faulty.
Check the Cables
If the battery light only flickers occasionally, it could be due to a loose connection, so ensure that all the cables are connected securely. Use a wrench or spanner to tighten each connection.
Look also for any signs of damage to the cables. It might be due to stress or rodents. Replace the cable if you see that it is damaged.
Check the Serpentine Belt
The serpentine belt couples the alternator with the engine’s crankshaft.
A slack in the belt can cause slipping, which will not allow the alternator to spin at its normal speed. The lower rotation generates low voltage. A broken serpentine belt will not allow the alternator to spin, producing zero voltage.
Inspect the serpentine belt for any slack or damage. Tighten it if there is slack, and replace it if it’s broken.
Check the Battery’s Terminals
If corrosion has accumulated on the battery’s terminals, clean it off.
The less the corrosion, the lower the resistance to current flow. There should not be any corrosion on the terminals at all.
Also, check the terminals to ensure the clamps are securely tight.
Check the Battery
If all the connections are secure, the cables are fine, and there is no corrosion on the terminals, the problem might be with the battery.
Is the battery close to, or past, its expected lifespan? If so, it might be too weak to hold a charge.
You can check the battery’s voltage and monitor it using a voltmeter or multimeter. It should normally be between 12.5 and 13.5 or slightly higher, but not less than 12.5 volts. If you measure it while the engine runs, it should be around 14 volts (or a little less or higher).
If the voltage level is constantly below the minimum level of 12.5 volts, it confirms that the battery is either too weak, old, or damaged to get charged and needs replacing.
The battery is very weak if the voltage is less than 12 volts. If it’s close to 0 (zero) volts, it’s most probably dead. Either that or it’s not getting charged due to a loose connection or a problem with the alternator.
Check the Alternator
If you’ve checked all the cables and are satisfied with the battery, you might suspect the alternator.
You can try fixing it yourself, but you’ll probably have to take the car to an auto electrician. An electrical short or open in its windings might interfere with the output voltage, usually 13.5-14.5 volts.
References
Wei Liew. A Guide What To Do When Battery Light Illuminates. (Self-published). 2023.
Video References
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Alternator-battery system
Car Manufacturing
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