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There are two ways to do this in your car.

You can either install a high-power relay between the alternator and battery, and switch that, or you can install a switch in the field wire from the ECM. Either way will make the battery light come on while the switch is off, which works as an indicator to remind you to turn it back on. You should couple that with a volt-meter, and turn the alternator back on if you get much below 12VDC on your battery.

I'm waiting for my EF service manual to load up, so I'll post the wire diagram for the alternator in a few mins.