Stereo cutting out

[Ivan141]

First problem:
Your alternator is probably dead. Voltage should be around 14-15 volts while driving, does the battery light light-up on your dash? 10 volts is pretty low for a healthy battery so it's either draining from lack of charge or you indeed have a bad battery. First things first though: check your alternator. about 14~15 volts charge voltage at the battery terminals is normal at idle.

If the voltage at the radio is going from 11 to 3,5 I would start worrying about an intermittant short circuit. But try measuring again with the radio out.