How long does it generally take to fully charge a car battery?
2 Answers
If the car battery is in a state of insufficient charge, driving the car at a constant speed above 2000 RPM for approximately 30 minutes can fully charge it. 1. Car charging principle: There is a generator next to the car engine, which is driven by the engine's belt to rotate and generate electricity, supplying power to other parts of the vehicle. At the same time, the generator charges the battery, ensuring a continuous source of electrical energy. When the car is idling, the generator's voltage (i.e., potential difference) can meet the charging conditions. Although the current is low, it is generally sufficient, provided that high-power devices such as the air conditioner, high beams, car audio, or refrigerator are not used. Otherwise, the generator's maximum output power may be exceeded, leading to battery depletion and permanent damage. 2. Severely depleted batteries require a charger: For batteries that are severely depleted, using a dedicated charger is the correct approach. Relying on the car's generator for charging takes a significant amount of time and is not very effective. During routine maintenance, it's also important to monitor the battery's condition. After parking, all electrical devices in the car should be turned off to avoid prolonged inactivity, which could lead to battery depletion. This might prevent the car from starting normally the next time it is used.
I think this is a good question now because it touches on a common doubt encountered in daily driving. Whether a car can be fully charged while driving depends on the type of vehicle. For conventional gasoline cars, the alternator charges the 12-volt battery while the engine is running, usually taking anywhere from several dozen minutes to an hour to replenish it fully—no need for intentionally prolonged driving. As for hybrid vehicles, like those from Toyota, the engine also charges the traction battery while operating, with the charging time depending on driving conditions. For instance, highway cruising might allow significant charging in 30 minutes to an hour, whereas stop-and-go city driving is far less efficient. Pure electric vehicles, on the other hand, can only recover energy through regenerative braking while driving and won’t actually reach a full charge—plugging in while parked is necessary for that. Many factors affect charging speed, including driving speed, air conditioning usage, and battery aging. From experience, I’d suggest not obsessing over incomplete charging while driving; just drive normally, as maintaining battery health is ultimately more important.
