How Long Does It Take To Charge A Car Battery While Driving?

**It takes about 30 minutes of driving to charge a car battery while driving completely, provided the battery was nearly charged before starting**.

In a modern car, the engine speed should be around 1,500 rpm or more to ensure it’s charging properly.

How long it takes is affected by the following:

1. The charge level when starting
2. What components are switched on (lights, radio, etc.)
3. Condition of the battery and alternator
4. Engine speed

The answer to this question applies to every driver, especially those who regularly complete short, intermittent trips.

Make it last as long as possible by never using the lights or radio while the car is switched off. Only use the essential electrical appliances at all times.

If work or school is only ten minutes away and you have to pass through twenty sets of red lights to get there, your car battery will probably be a little worse for wear.

This guide will address how long it takes to charge a car battery (while driving) and how this operates. Let’s get initiated.

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Does A Car Battery Charge While Driving?

It certainly does. A car is equipped with a 12 V (12.6 V) battery. This functions in much the same way as any other battery, like the one on your cellular phone or small laptop.

When you turn your car key to the START position, the battery sends a substantial amount of electrical power to the starter motor. This cranks (turns) the flywheel, giving the engine the momentum it needs to run under its own power.

When it sends all this power to the starter, the battery is discharging. It’s a vital and completely normal part of how a car works.

As soon as the engine’s running, it ignites everything into motion. Attached to the crankshaft – the spinning mechanical output at the bottom of the motor – is the alternator (along with other components, such as the AC compressor and power steering pump). It’s linked via a belt.

The alternator is essentially a comparatively large electromagnetic generator. It recharges the battery as the engine rotates. These days, provided the engine is turning fast enough (at least 1,500 rpm), the alternator should recharge the battery at the same rate, regardless of rotational speed.

How Does An Alternator Work?

An alternator rotates a magnetic core inside an armature coil. This spinning magnetic field induces magnetic flux, generating a current.

Slip rings feed the excitation current to the armature, and the stationary coils produce the alternating current.

The voltage regulator helps maintain a relatively steady voltage output. If the output (terminal) voltage is too low, the voltage regulator increases the input (field) current. Likewise, if it’s elevated, it decreases the field current.

The voltage regulator ensures the alternator charges the battery with between 13.5 and 14.5 Volts. In specific situations, the charging voltage can go substantially higher. That’s why a battery tester (which you should use quite regularly) displays these readings when the engine’s running.

Almost all the electricity generated by the alternator goes straight to the battery as DC. Here, it charges the cells. The battery will immediately require most of this power to run the electrical components within the car. Switch as many of these off as possible.

Still, over time, the battery will become completely charged again while driving.

Best Way To Charge A Car Battery While Driving

The best way to charge a car battery while driving is to journey along the highway relatively fast, for around half an hour. As a general guideline, you should be aiming for speeds of around 55 mph or greater.

**A 30-minute journey would be adequate for a weekly top-up of your battery**. If it’s already on low charge when you get in (if you’ve been using a lot of electronic appliances recently), you may need to drive much farther.

You should know that the motor’s speed matters here, not the vehicle’s. It should be running at a minimum of 1,500 revolutions per minute.

Essentially, you don’t want the engine to be idling. Anything above 1,500 rpm should produce adequate charge for the battery to manage the alternator’s voltage regulator field current and power the remaining car while replenishing.

Sitting in the car while the engine’s running could be illegal when you aren’t going anywhere. However, technically speaking, your vehicle would charge if you simply sat on your driveway for half an hour with the car in neutral and your foot placed on the gas pedal.

That doesn’t make much economic sense, though – plus, it might not be lawful (although nobody’s likely to call the cops on you, someone could). If you’re going to run your car for half an hour, you may as well go somewhere.

Other Ways To Charge A Car Battery

If your car starts, just drive it. The alternator should recharge the battery if you follow the steps mentioned above. If you frequently complete short journeys (see the next section), go for an extended drive once per week.

Your car could sit motionless for weeks at a time – Covid lockdowns, for example. Removing your battery and connecting it to a trickle charger will keep it in the best possible condition.

Find yourself with a dead (“depleted“) battery? Jump-starting or bump-starting is the ideal way to go.

Jump starting involves using jumper cables from another vehicle or electrical system to transfer electric current to your car’s battery. This should enable your car to operate on its own. However, bump starting works differently by utilizing the gears to trigger the engine into operation, as long as the ignition switch is turned on.

How Should I Charge My Car Battery While Driving If I Only Make Short Journeys?

The ideal approach is probably to select the appropriate car in the first place. Most internal combustion engines are designed to run – they need to power an entire vehicle, after all.

If you’re a city driver, these low-rev journeys will be unavoidable. A typical internal combustion engine (ICE) car will, by its very nature, struggle with these over time. Still, you probably won’t notice any problems for tens of thousands of miles.

Plan for the future with a hybrid or electric car (EV). The infrastructure isn’t quite complete yet, but increasing fuel costs and inflation mean that owning an EV may soon be more economically viable than a gas or diesel model.

Of course, these cars are powered completely differently from “conventional” vehicles. However, remember that hybrids, in particular, are specifically designed to handle slow city driving. You should find you have few problems if you purchase a dependable, warranty-covered model.

Does A Car Battery Charge Faster When Driving?

“How long is a piece of string?” How quickly a battery charges depends mainly on a few essential factors:

• Battery charge when the engine’s turned on
• Electrical load (lights, fans, radio, heated windshield, etc.)
• Alternator, battery, and electrical circuitry conditions

In general, yes – a car’s alternator will charge a battery quicker than a mains electrical charger.

This is because most car batteries have an average charge storage capacity of 48 Ah (Amp-hours). A car puts out significantly more current than most mains chargers.

It’ll take a car less than an hour to fully replenish the battery’s charge. In comparison, you should expect a regular charger to take at least 4 to 6 hours to restore the same battery.

A trickle charge will, of course, take longer – perhaps up to two or three intervals.

Note: It isn’t always safe to use mains battery chargers! You should always check the instructions on the battery to ensure it’s safe!

Does A Car Battery Recharge Itself While Driving?

A battery doesn’t technically recharge itself. The alternator replenishes it as you drive. The “electricity” (let’s keep things simple) then goes directly back out into the car’s electrical system.

It should take around half an hour, although it depends on various factors (see the previous section).

Conclusion – How Long Does It Take To Charge A Car Battery While Driving?

The exact amount of time it takes to charge a car battery while driving depends on a few factors. The most crucial thing you can do is avoid discharging the battery while the engine’s off by ensuring everything is turned off.

1. The better the battery’s condition when the engine switches on, the faster it’ll charge.
2. Turn off your lights, fans, radio, heated seats and windshields, and whatever else you can think of to make the battery charge quicker.

A car battery in superb condition, starting from a reasonable charge, should be fully recharged in 30 minutes.

Read your owner’s manual! These will give you all the directions you need to care for your car’s battery and keep the electrical system in excellent condition!

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