Calculating the time it takes for a battery to fully charge
The answers (mine and others) to the question you cite adequately cover your query.

A battery or battery charging system USUALLY specify voltages in a limited range. In such cases, mA input is an indication of charge rate if the system will accept the offered current. 

In a small percentage of cases a system will tolerate a wide range of input voltages, with voltage being converted internally to meet requirements. In such cases supplies with the largest I x V product will charge fastest. When supplies have different V specs BUT the same power spec then both are nominally equal but the system is liable tom operate optimally at a voltage which makes one or other slightly faster. 

Generally, for systems not designed to accept a wide range of input voltages. applying a voltage much greater than specified may result in destruction.