That little warning light illuminating on your dashboard indicating alternator problems is worrisome. How long do you actually have before the engine dies without a functioning alternator to charge the battery? Thankfully, a reasonable amount of time in most cases.
This article dives into details on how long your car can be driven once the alternator stops charging, what to watch for, best practices, and steps for maximizing the remaining battery power. Read on to better understand if you can make it safely to your mechanic when struck with alternator failure on the go.
Table of Contents
- Key Facts About Driving With a Dead Alternator
- How Does the Charging System Work?
- Key Factors That Determine How Long You Can Drive
- Voltage Gauge Readings When Driving Without an Alternator
- Maximizing Driving Time With a Dead Alternator
- Signs the Alternator Will Soon Fail
Key Facts About Driving With a Dead Alternator
Here are the quick essentials on how long you can drive once the alternator quits:
- Most vehicles allow 30 minutes to 1 hour of runtime once the alternator dies and battery discharges.
- Runtime heavily depends on amp load from accessories like lights and stereo. Minimize load to maximize available runtime.
- Outdoor temperature also impacts available power – cold weather further limits cranking amps from the battery.
- Keep driving at higher RPMs near 2000-3000 rather than idle to allow the alternator to produce some residual power from engine spin.
- Monitor the voltage gauge – sluggish cranking or voltage below 10V indicates time is almost out.
The basic advice is to turn off all accessories, drive fast but safely to your destination and get repairs immediately to avoid being stranded once the alternator fails.
How Does the Charging System Work?
To understand drivable time without an alternator, let’s quickly cover what the charging system does:
The alternator generates electricity to recharge the battery while the vehicle is running. It spins via a belt connected to the engine to produce around 13-14 volts needed for vehicle electrical systems.
This powers all electronics, accessories and charging requirements. The battery acts as a power reservoir when the engine is off. But it is continually recharged by the alternator when operating.
With the alternator broken, the battery must carry the entire electrical load which drains down quickly. Let’s look closer at factors impacting remaining runtime.
Key Factors That Determine How Long You Can Drive
Here are the main factors that come into play with how long your car will run once the alternator stops charging:
1. Battery Capacity and Age
A large, newer battery with full cranking power will allow longer runtime than an old weak battery unable to hold a full charge. High performance or large SUVs often have upgraded batteries.
2. Electrical Load Requirements
The more power your car requires for headlights, stereo, power windows and other accoutrements, the faster the battery will discharge when not being charged.
3. Ambient Temperature
Cold weather makes it harder for the battery to produce power. Heat is required for the chemical reaction. Frigid conditions may cut runtime in half.
4. Engine Size
A larger engine requires more turnover current to start, taxing the battery. Larger alternators in big SUVs and trucks expect higher loads.
Checking voltage gauges helps provide clues on remaining runtime once the alternator dies. Let’s look at those key indicators next.
Voltage Gauge Readings When Driving Without an Alternator
Here are the voltage levels to monitor and what they mean:
- 14+ Volts – Normal charging voltage with engine running and alternator functioning normally.
- 12-13 Volts – Alternator no longer charging but battery still providing power. Time to get repairs.
- 11-12 Volts – Battery is nearly depleted. Engine will soon begin sputtering as voltage drops.
- 10-11 Volts – Car is on the verge of stalling. Battery almost out of juice. Pull over and stop immediately.
- Below 10 Volts – Engine will stall with almost no cranking power left from battery. Operating voltage is critically low.
Monitoring your volt gauge gives you a countdown of available runtime as the battery discharges after the alternator failure.
Maximizing Driving Time With a Dead Alternator
To stretch your available minutes before the engine dies without a functioning alternator:
- Turn off all non-essential loads – lights, heated seats, stereo and accessories.
- Shift to neutral and rev engine higher when possible to generate power for battery.
- Drive faster to increase alternator spin rather than idling at stop lights. But drive safely!
- Lower windows and switch off AC to reduce load. If it’s nighttime, use parking lights only when required.
- Head to an auto parts store for a replacement alternator if nearby. They can test battery also.
- If stalling, use inertia and avoid braking to coast as far as possible while steering.
Gaining every possible minute helps get you parked safely off the road before losing electrical power completely.
Signs the Alternator Will Soon Fail
Be aware of early warning signs of impending alternator problems:
- Headlights or interior lights gradually get dimmer.
- Voltage gauge needle drops far below 14 volts when accelerated.
- Battery no longer holding a full charge between drive cycles.
- Whining noise from alternator indicates internal bearing wear.
- Smell of burning rubber as belts slip on pulleys from lack of charge.
Catching minor symptoms early provides more reaction time before alternator failure leaves you stranded.
With vigilance to voltage gauges and disabling power drains, most vehicles provide 30-60 minutes of drivable time once the alternator stops charging the battery. But move quickly to a repair shop or safe parking spot as stall conditions can arise rapidly. Watch for early warning signs of failure and avoid pushing limits when diagnosing charging system issues on the road. Schedule repairs promptly to avoid getting caught without power down the line.