From Peukert's Law, we know that when discharging a lead-acid battery,
if the discharge rate is high, the effective capacity of the battery
will be reduced due to the battery reaching a minimum cutoff voltage
earlier... the battery must be allowed to recover to a higher voltage
before discharge can resume
It's a bit more than that. If terminal voltage was the only issue you could just specify a lower termination voltage under load, but at high current the available current becomes limited by charge mobility. Having a rest period allows the slow moving ions to 'catch up' and produce higher current again for a while longer.
This effect isn't normally seen during charging because the charge current is much lower (typically C/5 or less). During charging the main issue is keeping the voltage low enough to avoid gassing.
If charging a lead-acid battery to a given absorption voltage (say,
2.45V per cell), will a battery reach that voltage after consuming less total energy if charged at a higher C-rate?
It will store less energy due to reaching the maximum permitted terminal voltage earlier, as a result of higher voltage drop across the battery's internal resistance at higher charging current.
If this happens, can the battery be charged further (without
overcharging the cell) by allowing the voltage to "recover" as can be
done while discharging, and then continuing at a lower charge rate?
Yes, but having a 'recovery' period doesn't help much. Simply maintaining a fixed voltage and allowing the current to reduce by itself works just as well and is faster.
in a proper CC/CV/float charge process, will this ever happen, or will
the reduced charge current during the CV and float phases ensure that
any additional charge the battery can take at a lower current, it
In CC/CV float charging the voltage is held at a level which ensures the battery can't gas no matter how long it is charged for.
This is different from multistage charging which uses a higher voltage during the absorption stage, then drops back to float voltage when the battery is fully charged. During the absorption stage some gassing may occur. Sealed lead acid batteries can recombine the gasses provided the pressure doesn't get too high and cause venting.
Some chargers can also apply an even higher 'equalization' charge at the end of the absorption stage, to ensure that all series cells in a battery get fully charged, and/or 'refresh' charges to allow maintaining a lower float or storage voltage without risking sulfation.