Time of charge of a battery
Charging time depends on a very large number of factors and so capacity and current are insufficient information to make a good calculation. For example, for a typical lead-acid battery you don't charge beyond 75% capacity at a constant current.

You can trade off battery lifetime against charging time. The appropriate charging current isn't arbitrary, A 100 A charging current won't charge a battery 1000 times faster than a 100 mA charging current, in part because heating the battery affects the charging process and capacity.


From Battery University

Many people do use a rule of thumb for lead-acid batteries that assume 80% charging efficiency and simply divide capacity in amp-hours by charging current in amps and add about 20%. Realistic charging efficiencies can vary considerably.

See also Peukert's law.

For other types of battery chemistry, different rules apply.