electrical issues

Having problems powering sat nav. currently power my sat nav via a usb port direct from a 12v battery charged from a 12vdc feed from a regulator, however The USB port regularly fails tried different types with varying degrees of success, the regulator delivers spikes of around 16v when engine revved, I have tried different regulators and they all do the same, do I need a device between the battery and usb port to even out the voltage to around 12v, is there such a thing.
it is annoying, I want to keep a battery so can charge mobile phone etc while stationary.
it is annoying, I want to keep a battery so can charge mobile phone etc while stationary.