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Yes, DC-DC regulator is capable of up to 28 or even 30V I think, so no problem there, as it will provide nice 5V and everything stay the same. Please however know that direct 12V input/output lines are not regulated, meaning you will have to get 24V fan instead of 12V or get external DC-DC regulator (~2$) for it. :) Very simple solution in each case :)