[Frango100]

The voltage is not the problem, but the total current draw could be. The existing wiring was planned for the standard fog lights with some reserve. So now it all will depend on how much the total current draw will be. Too much current through a too thin wire will heat up the wire and could melt the insulation or even melt the whole wire. The fuse, which is in the circuit to protect the wiring for too high currents, will melt before the wiring gets damaged. For that reason you should never change a fuse with a higher amp.
You could eventually use a separate wiring for the new fogs with a relay, which will be switched by the old fog lights power.