Do Car Batteries Charge While Idling? (2024)

FAQs

Do Car Batteries Charge While Idling? ›

At highway speeds, your engine's running hard enough for the alternator to send spare amps to the battery. But when parked, the engine doesn't have spare amps. No, you can't charge a car battery while idling. At best, it'll charge the battery a few amps, but not nearly the hundreds of amps it took to start the engine.

Some people suggest idling your car for 15-20 minutes to recharge the battery, but this is not always recommended. Many modern cars are equipped with sophisticated battery management systems that are designed to help extend battery life. This technology may also limit your car's ability to charge at low RPMs.

Does revving make a difference? When idling, the engine is still turning at a certain revolution per minute (rpm) – so the alternator is still converting that into usable energy and charging the battery. But revving the car a few thousand rpm faster does actually make the alternator charge the battery faster.

A lot can depend on what condition your car battery is in. If you know your car battery is relatively new and has been kept in good condition, it can probably sit unused for about two weeks before it goes flat, however in other cases a car battery can last between two weeks to four months.

Electric components of your car, like the lights and radio, put a strain on your battery, especially when the car is idling.

No, you can't charge a car battery while idling. At best, it'll charge the battery a few amps, but not nearly the hundreds of amps it took to start the engine. After a few days of starting and then idling the engine, you'll steadily deplete the battery instead of charge it.

Whatever myth you've heard, you cannot charge your car battery with 30 minutes of driving. The car's alternator is not a car battery charger. Yes, your alternator can charge your car battery—if you're driving on the highway for hours. Driving for 30 minutes is enough time to warm up your car battery.

During short trips, your vehicle's engine may not run long enough for the alternator to recharge the battery adequately. Over time, this can damage the cells inside the battery to the point that it struggles to hold a charge — a massive bummer if you don't have a battery warranty.

Alternator may not generate sufficient charging voltage until alternator speed is greater than about 2000 RPM. Typically, alternators have their full output rated at 6000 RPM but can continue to spin up to 12,000 RPM or more without any additional increase in output.

However, the alternator requires some power for the car's other electrical functions, so only 50 amps are available for charging the battery. Theoretically, it would take 90 minutes to fill the battery from empty. Topping up 20% would require one-fifth of that time, or about 17 minutes.

How often do you need to drive a car to keep the battery charged? ›

By driving your car at least once a week, you'll keep the alternator charging the battery even without a trickle charger. Plus, you'll be able to check out all the systems in the vehicle including the suspension components, power steering, braking, and transmission.

The abrupt motions of daily driving like quick starts, driving around corners, and panic stops could loosen your car battery. If your battery loosens too much within your engine, this could lead to excessive vibration, which will put a strain on your battery, the surrounding components, and its circuits.

Some of the possible reasons why your car battery can be drained overnight include accidentally leaving the lights on, having a faulty relay causing parasitic draw from accessories, and failing to replace an underperforming alternator among others. Experts recommend replacing your car battery every four or five years.

If you do leave your car running for too long, you might experience a few unpleasant side effects: As mentioned, your car's engine continues to consume fuel so long as it's powered on. But it also consumes power from your car's battery because the engine and alternator both run slowly whenever your car idles.

“Electrical devices or lights left running, a defective charging system or alternator, and extreme weather are some common reasons but maybe it's just time to get a new battery.”

If you find that your car battery is dead after not being driven for only a few days, there may be anunderlying issue causing this such as: Corroded battery connections. An electrical issue drawing power. Parasitic drain causing battery loss.

By driving your car at least once a week, you'll keep the alternator charging the battery even without a trickle charger. Plus, you'll be able to check out all the systems in the vehicle including the suspension components, power steering, braking, and transmission.

Can a completely dead battery be recharged? If the battery is your only problem and the car is in otherwise good working order, it is quite possible to completely recharge a completely dead battery. Using the charger or a jump start or push start and then letting the engine idle with electrical items switched off.

In order to charge a dead car battery, a set of jumper cables and a functional car with a charged battery is required. You will then have the ability to connect the batteries to one another using the jumper cables, and recharge the dead battery by transferring energy from the functional battery.

Allow both vehicles to run connected for about three minutes. Leave the jump-started vehicle running and disconnect the cables in the reverse order that they were attached and close the hoods. Keep the jump-started vehicle's engine running for about a half hour to allow the battery to fully charge.