Battery Kill Switch Question

[ronnieroadster]

When I read the rule for batteries it says a main disconnect switch on the positive lead of the battery.
 Knowing the main battery controls the engine and fuel delivery system the kill switch disrupts power to the engine and fuel. If there's another small sealed battery only used for data or an air pump must that also be connected to a disconnect switch?

[SPARKY]

Miss Liberty has a secondary battery for data logging, its ground cable has a solenoid in it with its own switch on the switch bar out side of the master switch. The battery disconnect at the back of the car also kills the power from the secondary by depowering the solenoid.

[manta22]

Mine has a big switch that turns off the battery positive 12V. It is actuated by a push- pull control cable in the nose of the car.

I also have a big relay that shuts off all 12V power if the impact switch is triggered or the guarded toggle switch on the panel is flipped.

Regards, Neil  Tucson, AZ

[Elmo Rodge]

Good question Ronnie. I'm anxious to hear the answer.   Keeping both of those things operable could be quite handy. Wayno

[johnneilson]

As I recall, the main switch is to shut down motor and fuel feed in case of a roll cage test session.
Your data and vent fan should be OK on separate power.

As always, the opinions posted here are just an opinion worth less than or equal to what you paid for it.

John

[Sumner]

As I recall, the main switch is to shut down motor and fuel feed in case of a roll cage test session.
Your data and vent fan should be OK on separate power.

As always, the opinions posted here are just an opinion worth less than or equal to what you paid for it.

John

You might be right but I'd think you are trying to cut off all electrical to avoid possible sparks from any battery.  We run the solenoid to cut off the data battery.  

We and others should also think about doing what is required in boats and that is have a fuse on any battery within 6 inches of the battery which should also kill the battery with a short although a short on a small wire could still burn the wire up and not blow the fuse.

I use these....





...now and will also use them on the lakester.  They mount right on the battery and .....



....  you can buy fuses in different sizes.  Not that much money and they could kill the power in a major accident well before help got to the car maybe preventing a fire. I've gotten them from here...

http://www.genuinedealz.com/marine-electrical-supply/fuses-and-blocks

Sumner

[jdincau]

     Speaking as an ex inspector, here is my take;
    The battery disconnect switch is not a kill switch, it is used to remove all electrical power so the first responders do not have to worry about causing sparks when extricating the driver from the vehicle. Our modified roadster has a 12 V alarm battery used to power the tach, it has a disconnect switch.

[johnneilson]

     Speaking as an ex inspector, here is my take;
    The battery disconnect switch is not a kill switch, it is used to remove all electrical power so the first responders do not have to worry about causing sparks when extricating the driver from the vehicle. Our modified roadster has a 12 V alarm battery used to power the tach, it has a disconnect switch.

The book doesn't state an objective, it merely says to have a disconnect means and where to locate it. Also, it does not state which side of battery to switch.

I would argue that killing the motor and potential fuel leakage is more important, but likely will not satisfy anyone here.

In other sanctions of racing, the tech inspection of the "battery disconnect switch" is to kill the motor and make sure it overrides the alternator.

John

[Seldom Seen Slim]

Which side of the battery should be opened by the disconnect switch?  The NON-grounded one, whether positive or negative.  If the hot side is not disconnected the entire vehicle will be energized to the battery's voltage, and therefore a piece of metal that falls across the ungrounded battery terminal/cable will conduct, and that's not a nice thing to do to safety workers.

[manta22]

Jon;

If you break the battery ground connection the positive 12V lines can be shorted to ground without causing a problem because the current path back to the battery negative terminal is open. Theoretically, either the - or + battery connection can be broken by a switch; most builders prefer the + (positive) conductor but that's only due to convention.

Regards, Neil  Tucson, AZ

[bearingburner]

What do you recommend for KAP (keep alive power) to your vehicle's computer?

[Seldom Seen Slim]

Neil said:  "...Theoretically, either the - or + battery connection can be broken by a switch; most builders prefer the + (positive) conductor but that's only due to convention."

I was careful to leave "positive" and "negative" out of my comments -- because there were and probably still are those that ground the hot side of the battery.  Whatever -- sure, there's gotta be a completed circuit for them there little electron-thingies to meander upon to make stuff work -- stuff like the cigarette lighter and the big-a** spark generator and that kinda stuff.

ZAP!!

[Peter Jack]

What do you recommend for KAP (keep alive power) to your vehicle's computer?

Just an observation. If the master kill switch has to be used, probably the retention of data is the least of your worries. If you've got time before you want to use the master kill switch you can probably attach a supplementary power source for the computer before you shut down the main system. I'm of course ignoring the fact that the data could be used for accident investigation but then it should be on some sort of recording and storage system.

Pete

[johnneilson]

Peter,

You are right about the retention of data, however, in some systems power is required to retain the data.
It doesn't take much, small battery is used.

J

[4-barrel Mike]

http://www.landracing.com/forum/index.php/topic,1331.0.html

Mike