If the battery is only discharged to 50% of its capacity, then the recharge time is only half as long (approximately).
With an enhanced 3-mode charger, the battery is 100% recharged at the end of the charging cycle. A standard(non-Ibex) 3-mode charger recharges the battery to somewhat less than 100% at the end of the charging cycle (App Note 4 discusses various types of chargers).
The situation is more complicated, however, if a 2-mode charger is used. With this type of charger, the battery is not completely recharged at the end of the charging cycle. The recharge level depends on the charge rate. For instance, a 1A charger recharging a 5Ah battery yields a charge rate of C/5 where "C" is the term used for the battery's Ah number.
The following list shows the recharge level of the battery after the 2-mode charger finishes its charging cycle. After the charger finishes its charging cycle, it switches to float (maintenance) mode. In this mode, the battery eventually reaches a 100% recharge level, but it takes an additional 2-3 days.
C/3 charge rate --> 75% recharged
C/5 charge rate --> 85%
C/10 rate --> 90%
C/20 rate --> 95%
C/100 rate --> 100%
If a load is also connected to the charger while the battery is being recharged, the amount of current "stolen" by the load effectively reduces the current rating of the charger (as far as the battery is concerned). This should be taken into account when calculating the charge rate.
Note that a standard (non-Ibex) 3-mode charger should not be used to power a load while charging a battery (it may lockup in fast-charge mode). An enhanced 3-mode charger, however, can simultaneously recharge a battery while also powering a load.