nhra cutoff switch and battery backup

long story short i put my battery in my trunk, to run at the track i need a cutoff switch

already figured out all the wiring and how its going to work, just wondering whats going to happen with my battery backup for my alarm, its not keyed

if i put the alarm in valet mode will everything be alright?i dont think they will let me pass tech if the alarm goes off when they flick the cutoff switch

alarm is a viper 5901

92 mustang

no one?

you can wire the 5901 to the battery side of the cut-off switch or at the positive post of the battery.
you only need to run the red constant 12v wire. the rest should be ok.

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This information is provided only as a reference.
All circuits should be verified with a digital multi-meter prior to making any connections.

FWIW - a cut-off switch... (?? For what?)

I'm used to "Isolation Switch" and "kill Switch" jargon.

An Isolation Switch normally only isolates the battery. Hence it is usually in the battery -ve connection (for safety).

A Kill Switch normally kills the engine. Hence it removes ignition power or shorts the points (etc) for petrol engine, or cuts fuel (etc) for diesels.


But some DEFINE an Isolation Switch (or Kill Switch) to BOTH kill the engine AND isolate the battery.
In such cases - assuming a mere heavy SPST isolation switch - the battery and alternator remain connected and the switch isolates the +12V to the rest of the vehicle.

NHRA rules requires that certain vehicle configuration have a manual switch installed accessible from the outside of the vehicle in order the cut-off or isolate the battery. This is a safety requirement.

-------------
This information is provided only as a reference.
All circuits should be verified with a digital multi-meter prior to making any connections.

Sorry 91stt - I only just noted your reply.

So NHRA rules specify an Isolation switch - it does not have to kill the engine, and hence - for safety - should be in the ground connection from the battery to switch(es) wherever and the to chassis/body & engine.   


The alternatives are:
--- +12V battery isolation for less-safe "isolation" (ie, where the battery +12V terminal does not short to GND nor does its connection to the isolation switch - eg, adjacent to the battery, or on the dash, or on rear external corner of vehicle etc depending on the regulations), or
--- alternator (B, B+) connected to the battery +12V and the isolation switch between the battery&alternator and the rest of the vehicle where the "isolation switch" is to "isolate AND KILL" the (battery and) engine. IOW - the alternator is not isolated from the battery.

The starter-motor power feed can be isolated via the isolation switch iaw whatever the regulations require. (Some require "all" +12V feeds to be isolated.)

So for safety it's usually (and should be!!) the battery-ground isolation except where a kill is also required in which case only the latter works.

The above assume a single isolation switch. Remote isolation via relays or combination isolate&kill alternatives using complex switching or relays can be used but is usually avoided due to reality (ie, implementation has a higher risk than the "battery plus alternator" isolation) and is hence implemented only in critical situations where cost is not an issue (ie - redundant relays and connections).


Not that I have "officially" dealt with these issues in this CE millennium, but in my prior dealings the so called "authorities" were unable or unwilling to answer just what the intention of "isolation" was for. (IE - power isolation, accident short-proofing, stopping engines....) But regulations did change - eg, the addition that "isolation in the ground circuit was acceptable" clause. LOL! Acceptable? Isolation of the hot circuit was criminal (potentially, IMO), if not heavier and more expensive.
As to whether I think the isolate and kill functions should be combined, I now simply refer to the regulators. (But I do like motorbikes!)