How Long to Charge a Car Battery at 2, 4, 6, 8, 10, and 15 Amps?
Charging a car battery from time to time using dedicated car battery chargers may be required when the car is not being used over a longer period of time. Also, if the battery is discharged below a certain level and it can't crank the engine because some load was unintentionally left turned On, charging it with an advanced battery charger may prolong the battery's lifetime.
However, batteries of different sizes/capacities require different charging currents for "optimal" charging - too strong currents can even damage the battery, while too weak currents are unable to recharge the battery in an acceptable period of time.
Published: March 11, 2023.
Battery Capacity vs. Charging Current
Lead-acid batteries, regardless of the type (wet/flooded, AGM, Gel-Cell) have a maximum charging current which is usually around ~0.3C, and with a maximum recommended charging current around 0.15-0.25C.
Also, for lead-acid batteries, there is sometimes a minimum recommended charging current which ensures that the battery is charged with the current sufficient enough to break crystals of Lead-Sulphate during charging.
As a rule of thumb, fully discharged lead-acid batteries should be fully recharged during 10-12 hours of charging.
In short, the minimum charging current is usually around 0.1C, or the charging will last simply too long to be practical.
When choosing the right lead-acid battery charger, go for the intelligent AGM battery chargers that support charging of various lead-acid battery types (wet/flooded, AGM, Gel-Cell), that analyze the battery before charging and that also act as car battery maintainer when the battery is fully recharged.
Car Batteries Charging Time Table
The following table lists charging times of typical car battery sizes when being recharged using 2, 4, 6, 8, 10, and 15 Amps battery chargers.
Note: the batteries are considered to be discharged down to 50% DoD (50% SoC), although the car batteries should not be discharged below 20% DoD (80% SoC).
| Battery Capacity / Charging Current | 2 Amps | 4 Amps | 6 Amps | 8 Amps | 10 Amps | 15 Amps |
| 33 Ah | 8.5-9h | 4.5-5h | 3-3.5h | 2-2.5h | 1.75-2.25h | - |
| 45 Ah | 11.5-12.5h | 6-7h | 4-4.5h | 3-3.5h | 2.5-3h | - |
| 55 Ah | - | 7-8h | 5-5.5h | 3.5-4h | 3-3.5h | 2-2.5h |
| 65 Ah | - | 8.5-9.5h | 6-6.5h | 4.5-5h | 3.5-4h | 2.5-3h |
| 75 Ah | - | 10-11h | 6.5-7.5h | 5-6h | 4-4.5h | 3-3.5h |
| 85 Ah | - | 11-12h | 7.5-8.5h | 6-7h | 4.5-5h | 3.5-4h |
| 100 Ah | - | - | 9-10h | 7-8h | 5.5-6.5h | 4-4.5h |
| 120 Ah | - | - | 11-12h | 8-9h | 6.5-7.5h | 4.5-5h |
Of course, these times can vary even more, depending on the battery condition, age, exact chemistry, intended use, temperature, etc.
As one can see, 10 Amps smart AGM battery charger is perhaps the most universal battery charger for car batteries.
However, if You are regularly charging larger batteries (100+ Ah) that are deeply discharged (deep cycle batteries), consider getting a much stronger battery charger, perhaps in the 20-25 charging Amps range.
