What would happen if I used a battery charger rated for 230VAC 50Hz input here in USA where we use 60 Hz? Would it be ok? What side effects may happen because of the mismatch in input frequency with the specs of the charger? Is the reaction of the magnetic core of the charger to the different frequency the only concern I should have? What might this do long term to the charger? Might it fail prematurely? I would use 230V 60Hz input on this charger by using a pair of phase locked (but reverse phase) 115V 60Hz lines so it would be a true 230V 60Hz 15A capable power source.
Generically, it is less stressful for a transformer designed for 50Hz to operate at 60Hz. You did not include any critical details, so it is not possible to offer any definitive answer to your question.
You did not mention the dramatic voltage difference, so we must assume that you are connecting your battery charger to a 230V circuit rather than the common 115V branch utility circuits common in North America.
120Hz current pulses vs 100Hz current pulse will be about the same. if rectified voltage is same. Since current charge pulse duty cycle is same as % voltage ripple, and since f is increased 20% , sag time or ripple V is reduced and thus Ipk_charge/Iavg_discharge is your crest ratio, but ripple current in caps is rated for RMS so the Avg current is the same, the RMS current may be slightly higher. duty cycle* Ipk^2*ESR of caps (or using D.F. method) means caps may be slightly warmer at max load current. same for Diodes.
So bottom line, % ripple voltage is inverse to crest factor of cap current and ripple current and temp rise at full current. Verify self heating. If design margin is good and caps are not severely aged, Ok, otherwise replace caps with LOW ESR types and add passive power R to remove heat from caps.... depends on regulator if any and max charge current if adjustable.
But since the cap is your battery, charge current should not exceed battery rating.