Remote battery isolator (push button kill switch)

[Greg Amy]

The output circuit to the switch in the cabin is an isolated circuit with NO CURRENT...

Because the circuit that is run into the cabin is through the "load" first there really isn't any power flow to the switch.

You guys are both missing the (safety) point. The real safety point: Load is not important. Current is not important. Potential/voltage is important.

Let's take our "hot wire into the cabin" to a worse-case scenario. It's wired up in the "traditional" manner, with the Big Fat Wire going to an in-cabin manual switch. I get into a wreck and hit a wall HARD, crumpling the firewall. that crumpling crimps the Big Fat Wire at the firewall, grounding it to the firewall pass-through (despite using a grommet, it was a Really Hard Hit). That hot battery wire is now grounded, and very high amperage is now flowing directly from the battery to the chassis. Since I did not protect that wire with a fusible link or fuse at the battery, and due to the leakage of fuel from my fuel supply line, very soon POOF! Greggy Flambe.

No amount of manual kill switch is going to protect me from this, even the current (har-de-har) Luddite one. This is why I agreed with Chris' point above vis-a-vis the current "approved" designs (though I challenge the "approved" moniker, reverting to "ignored" or "accepted".) Of course, as I noted before, this can be alleviated simply by putting a fuse/fusible link on the hot wire at the battery.

Note this design is accepted simply because that CIRCUIT is actually switched by the kill switch; even though potential still exists at the switch, we accept the design because the switch opens the battery circuit.

Apply this to your remote kill switch design: if you still have POTENTIAL (read: voltage) to a wire that is not switched by the solenoid - regardless of its voltage - you have potential for current flow. Just as in the scenario above, if these wires were to become grounded in an accident, you will have current flow. Further, this is a circuit that is NOT switched by the solenoid, as is required by the rules.

I'm going to attempt to draw up my "design" this AM, to show you what I mean. My design can be built for probably less than $30 in parts using the ubiquitous Ford starter solenoid, some wiring and switches, and a little bit of time. It's cheap, safe, and meets not only the letter but the intent of the rules...

[Rabbit07]

Greg,

You can not use a ford starter soleniod. You need a continuos duty soleniod, which the Ford starter solenoid is not rated for. Other than that I follow what you were taking about earlier. I really like the fuse link idea or even a maxie fuse at the battery .

[Greg Amy]

Roger, Chris. However, I'm sure you don't need a $200 relay to do this...

I can't use the computers drawing tools for crud. And, I don't have my AutoCAD here at my desk. But, I have a scanner. Try this on for size; I'm betting it can be built for SIGNIFICANTLY less than the commercial versions.

Chris, feel free to spec out some good-quality components. - GA

[Rabbit07]

The N.O. Momentary is under the hood? That is the only thing I don't like because it would require getting out of the car to reset.

The parts I purchased recently for a T1 Viper only cost me $93.00. That ofcourse is just switches, and the soleniod, not wire and install. The switches are Honeywell MIL Spec parts and I forget the Manufacturer of the soleniod. When I get to the shop today I'll take a looksey.

[Greg Amy]

The N.O. Momentary is under the hood? That is the only thing I don't like because it would require getting out of the car to reset.

Exactly! But it has to be, Chris, otherwise you'd have a constant-voltage wire going into the cabin. That's the whole point of my resistance (har-de-har, part two) to the commercial designs as discussed above.

But, I relent that if that wire is fused it's just as "safe" as the Big Fat Wire design (with fusible link).**

Now, all that said, this adds many more components and several new points of possible failure into a system that is easily and simply handled with a fusible link, 10 feet of fat wire, and a $20 kill switch. I'm not necessarily convinced that this system would be any safer than a properly-designed Big Fat Wire system, and it's obvious that the complexity and number of potential failure spots is increased. - GA

On edit: ** As long as grounding those control wires does not result in energizing the battery solenoid. Your design above, Chris, does not meet that criteria.

[seckerich]

Actually Greg you are missing something yourself. The system I am talking about uses only a resistance check to actuate the circuit relay under the hood. When the relay sees zero resistance it closes the relay. If I hit hard enough to crush these wires the worst I have is a closed circuit, not a shorted battery. Think of it more as a PLC instead of a relay.

[Z3_GoCar]

You guys are both missing the (safety) point. The real safety point: Load is not important. Current is not important. Potential/voltage is important.

Let's take our "hot wire into the cabin" to a worse-case scenario. It's wired up in the "traditional" manner, with the Big Fat Wire going to an in-cabin manual switch. I get into a wreck and hit a wall HARD, crumpling the firewall. that crumpling crimps the Big Fat Wire at the firewall, grounding it to the firewall pass-through (despite using a grommet, it was a Really Hard Hit). That hot battery wire is now grounded, and very high amperage is now flowing directly from the battery to the chassis. Since I did not protect that wire with a fusible link or fuse at the battery, and due to the leakage of fuel from my fuel supply line, very soon POOF! Greggy Flambe.

No amount of manual kill switch is going to protect me from this, even the current (har-de-har) Luddite one. This is why I agreed with Chris' point above vis-a-vis the current "approved" designs (though I challenge the "approved" moniker, reverting to "ignored" or "accepted".) Of course, as I noted before, this can be alleviated simply by putting a fuse/fusible link on the hot wire at the battery.

Note this design is accepted simply because that CIRCUIT is actually switched by the kill switch; even though potential still exists at the switch, we accept the design because the switch opens the battery circuit.
.....

I'm going to attempt to draw up my "design" this AM, to show you what I mean. My design can be built for probably less than $30 in parts using the ubiquitous Ford starter solenoid, some wiring and switches, and a little bit of time. It's cheap, safe, and meets not only the letter but the intent of the rules...

Good point Greg, except my battery is in the trunk. So a cable will go through the passenger compartment no matter what. It's a good thing then that the fuel lines go down and underneath the other side of the chassis. I choose the traditional manual BCS, wired into the stock emobilizer relay. This relay is rated for continuous use for up to 40amps, plenty for the ignition and alternator field duties I use it for. When I switch it off with either a toggle or the BCS it provides a grounding path for the alternator field, so there's no run-on issues. These relays are commonly used in alarm systems and are inexpensive and avalible at NAPA.

[loopracing]

When I was running IT with the battery located in the stock L/F location (VW Scirocco), I used a standard Killswitch with alternator ciruit located about 6in. from the battery. I had made mounting bracketry that allowed me to use a push/pull cable to the handle and ran it to the dash to the left of the steering wheel. This made for a compact handle on the dash and no hot wires running into the car at all. This setup made for no more than 6in. of hot battery cable when the switch was off.

[Duc]

Actually Greg you are missing something yourself. The system I am talking about uses only a resistance check to actuate the circuit relay under the hood. When the relay sees zero resistance it closes the relay. If I hit hard enough to crush these wires the worst I have is a closed circuit, not a shorted battery. Think of it more as a PLC instead of a relay.

A short to ground for either wire will not cause the relay to engage. Only both wires being shorted together would cause the circuit to engage.

That is what they are talking about for the current detection. It is not any current detection, but looking for a very small current through the two wires being connected back to the internal circuit, not to ground.

Anyone find out if these are good rule wise? The more I think about these the more I like.

D

[Colin Harmer]

David,

I've had the cartek one in my ITA miata since I built it (got it from Demon Tweeks when I was over there a few years back) . Works like a champ, and I have a log book with a tech sticker in it...Big red button, when pressed kills the motor. Job done.

The only advice I'll give you is to run a battery tender on it when you're not using the car as my device puts a constant load on the battery which will eventually drain it.

Cheers,

Colin

[rsportvolvo]

Just to keep the options in a single thread. The Turner Motorsport BMW's use this switch with a toggle switch and switch cover mounted on the cowl.

http://www.batterycutoff.com/

[Duc]

Nice find. Looks rather reliable, does Turner us it on all of their cars?

[rsportvolvo]

Here's Will's reply:

"Hi David,
We use something like this. It's made by Power Switch Inc. The wiring is done “remotely” so that you only need a small external switch.

-Will"


I also got in contact with a friend, Marcus Haselgrove, formerly with B-K and Champion Audi. He said that Porsche, Audi, Lola, DP cars, etc. use a Kissling aerospace relay. A bit pricey as they're @ $500 per relay. For those interested PRS has one in their online catalog and here's the Kissling USA link:

http://www.kissling.de/english/start_e/start_e.html

Here's a picture of one mounted in a Porsche 911 (997) GT3 RSR (click picture next to "Electrical System"):

http://www.porsche.com/international...ogyandconcept/

Hope this helps folks out.

Now all we need is for Chris to post more info on the Viper Comp Coupe relay. It seems to be the most affordable option and good enough for a series production race car.

[mbuskuhl]

http://www.alliedelec.com/Search/Pro...C=&SEARCH=&MPN

I use the one above and so does an MX-5 cup team.