How long does it take to charge a car battery?

How long does it take to charge a car battery? Before asking how long to charge a car battery, we have to first look at the battery itself and the battery charger device we owned.

We need a proper battery charger device to provide the right current charge and voltage when recharging car battery. In addition, we also have to know how much battery capacity we have because battery charging time depends on the amount of battery capacity. The greater battery capacity needs a longer time than the lower one.

There are two familiar methods for recharging car battery: slow charging and fast charging. We can use both methods to measure how long does it takes to charge a car battery. Here they are the slow charging car battery and fast charging car battery.

I. Slow charging car battery

The slow charging car battery method is known as "normal charging" because it uses a low current to charge a battery. Slow charging needs only 10% until 15% from battery capacity amperage. For example, suppose we have a car battery with 60Ah (Ampere hour) capacity to use the slow charging method. In that case, we need at least 6Ah and a maximum 9Ah from a battery charger device.

Here's the formula to measure how long we need when charging a car battery in the slow charging method.

CT = (BC / CC ) + (20% (BC / CC ))

CT = Charging time (hours)
BC = Battery Capacity (ampere hour / Ah)
CC = Charging Current (ampere hour / Ah)

For example :

There is a 60 amp hour (60Ah) battery capacity. The minimum charge current to charge a car battery with slow charging method is 6Ah (from 10%x60Ah). So, the time needed to do slow charging for 60Ah car battery capacity is :

= (60Ah/ 6Ah) + ((20/100) x (60Ah/ 6Ah))
= 10 + (0.2 x 10)
= 10 + 2
= 12 hours

And if we use the maximum charge current (15%) for slow charging, here are the time needs to charge 60Ah car battery capacity:

= (60Ah/ 9Ah) + ((20/100) x (60Ah/ 9Ah))
= 6.6 + (0.2 x 6.6)
= 6.6 + 1.3
= 7.9 hours

So, suppose we want to recharge the car battery with a 60Ah capacity for 8 to 12 hours. In that case, we need 6Ah until 9Ah current charge from the battery charger. Slow charging is the recommended method to charge a car battery because it prevents overheating in the car battery and keeps the battery lifespan.

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II. Fast charging car battery

The fast charging car battery is the quickest time to charge a car battery. Still, it's better to avoid this method because fast charging uses a higher current than slow charging. Fast charging needs 20% until 40% charge current from battery capacity.

For 60Ah battery capacity, then we need 12Ah minimum charge capacity and 24Ah maximum charge current. The formula to measure charging time is the same as the formula we used for the slow charging method.

So here they are the time needed to charge a car battery with a fast charging method.

= (60Ah/ 12Ah) + ((20/100) x (60Ah/ 12Ah))
= 5 + (0.2 x 5)
= 5 + 1
= 6 hours

And for the maximum current charge for fast charging is :

= (60Ah/ 24Ah) + ((20/100) x (60Ah/ 24Ah))
= 2.5 + (0.2 x 2.5)
= 2.5 + 0.5
= 3 hours

Fast charging time is quicker than slow charging, but there are many risks if recharging a car battery with this method. Fast charging brings overheating to your car battery. It tends to damage the battery cell, so it reduces the lifespan of your car battery.