"RST Engineering" wrote in message
...
What do you want the cutoff voltage to be? Personally, I'd pick 13.0
volts, but it is child's play to do any voltage you want.

There will be about a milliampere of quiescent current for the sensor that
will still be on-line when the output shuts off.

Jim


One-chip solutions designed for this purpose that can detect both
undervoltage and overvoltage are available from several vendors, such as
Maxim.
Example: http://pdfserv.maxim-ic.com/en/ds/MAX6457-MAX6460.pdf

These offer very low quiescent current when off (couple of uA). The output
can be used to activate a relay (maybe needs an extra transistor). I think
you can request free samples.

Rob