Somehow I doubt that 100 volt number.
Sounds like a good way to make a buck.

Must be a very rare failure mode or car radios and EFI/IGN  computers
would be dying all over the place. With 12 volts applied to the
field how long before the wires feeding it fused?

With a battery across the output from the alternator the connection
to the battery must also somehow disappear as the battery
would look like a giant short to 100 volts.

Further more 35 volt zeners on the input to most electronic equipment
would do the job. Perhaps there could be a 100 volt spike but a
capacitor could handle that and knock it down to way less than 35 volts.

Color me skeptical.

Rob Weinstock wrote:

You can get an inductive spike of that amplitude. Normally, the lead-acid
battery provides excellent dc system filtering properties. If you were to
start the engine, then disconnect the battery, so that it is running on
alternator only, then you are at risk.

As far as the 35 Vdc Zener goes, it should work if the energy of the spikes
is low enough. There are DC transorbs available for this purpose now.

Regards,

Rob

You put a low resistance in series with the supply before the zener
to limit the zener current. The spike voltage is then dropped across
the resistor reducing the power dissipation in the zener.

Paul Lamar
 
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