You must consider many variables before determining how long a car battery takes to recharge. The battery needs to have enough internal cold cranking amps to turn the motor on when the ignition key is activated. Batteries are designed to last five years or so (depending on the quality and warranty) under normal driving conditions. Variables that hinder a battery from lasting that long can include corroded terminal and cables that do not allow the alternator to restore the battery during the operating time. A bad alternator also will suck the life from a battery as can repeated violations of the battery life, such as leaving lights on or other electrical components that require the battery to be jump-started often.
Maintenance-type batteries should be checked to ensure that the proper amount of distilled water is in each cell, though many of these types of batteries are being replaced with "maintenance-free" batteries. How dead the battery is and if there is damage to the cells also directly affect the charging time of the battery.
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Once a battery has turned the engine on, the alternator takes over and replenishes charge to the battery. If the alternator begins to fail, the vehicle is left with no other power source than the battery. Once the vehicle has sucked the life out of the battery with a bad alternator, it is rendered useless. Although an alternator will not fully charge a battery during operation of the vehicle, it may restore enough charge back to the battery to allow the internal cold cranking amps of the battery to start the vehicle on the next attempt.
Several types of battery charges have different options, and the settings on the charger will dictate the amount of time it will take to charge a battery. The most influential setting is the amp setting. The voltage setting should be 12 volts for an automobile battery unless otherwise specified on the battery label. The lower the amp setting, the longer it will take the battery to recharge. A low setting in amps is commonly referred to as a "trickle charge," and often batteries that have not been used in a while, such as a seasonal RV, can benefit from a trickle charge for a long period of time prior to usage. A medium amp setting of the battery charger will expedite the amount of time to charge the battery. Again, this will depend on how dead the battery has become. A 10 amp setting on the charger could take 40 minutes, or it could take a couple of hours.
Another common setting on some quality chargers is a high amp setting, referred to as the "start" setting, which can be used to jump-start the battery. You should be able to charge the battery in a short amount of time and start the engine with the charger. It would be recommended to run the vehicle for some time to restore the charge to the battery using this method if the battery was completely dead.
As long as the battery isn't damaged or have a bad cell, the better the quality of charger, the higher the amp setting, the less time the battery will take to charge. A battery that was completely dead should be charged overnight--even if it runs well after a quick charge--on a low-amp trickle charge.