Battery Cut Off

[G.Buckle]

At 07:54 25/03/97 +1000, you wrote:
>OK a slightly unrelated one for you guys and girls
>
>under our country's racing authority the battery isolation switch has to
>also shut the engine off. Currently most alternators go low on the load
>side and produce balisitic voltage in the abscence of the battery
>risking computers etc, and the car chugs on quite happily.

You could use a relay. Use the output voltage of the alternator to activate
it, and have it switch the battery voltage to the sense line. That way,
while the engine is rotating fast enough for the alternator to put out, it
still sees the battery voltage and won't try to wind the voltage up...