Pumpking.

About done with the car build and need to order a battery cut-off switch and get that wired in.

I see 2-post and 4-post options. I'm guessing if I have a stock alternator in place, I want a 4-post?

rudebwoy

iTrader: (1)

use a 2 post

Pumpking.

Alt --> Battery + --> Post 1
fuse box to post 2?

itspools

I still have an alternator and 12 volt system. I run this switch:

Moroso 74102, Moroso Battery Disconnect Switches | Moroso

m4xwellmurd3r

pretty sure it goes battery>cutoff>fusebox>alt

you don't want the alternator to be unfused.

basically take the positive battery cable, cut it in half, and stick the cut off in the middle. (don't literally do that, but if it gives you a better visual, well. you get the idea)

dohcsideSi

I just got the flaming river lever kit with the 2 post switch. I need to rewire it because I moved the battery back up front and my old moroso switch never actually killed the car.

I've seen every diagram on the interweb and understand how it's supposed to work but before I wire it I just want to make sure I'm not going to short my ecu or something.

I'd love to see actual pictures instead of ms paint drawings.

SPOOLINmatt

bat and alt to one post, the rest of the car to the other. simple

drmix

Just went through this on my car and this way does kill the car. Only needs 1 large cable running up front then a small wire for the main relay connection.

4 post switch

small post 1 - Ignition wire at main relay, harness side
small post 2 - Ignition wire at main relay, relay side
big post 1 - +12v Battery
big post 2 - Distribution block up front

When its shut off the ignition kills the car and cuts battery

Kevinio

Here I have created a few years ago a schedule for a FIA 6-post switch:

rudebwoy

iTrader: (1)

in addition to the diagram above, add an additional wire preferably 4 gauge, directly from the battery positive pole before the switch directly to the alternator unfused, this is the only way you will kill the car using the switch. (2 pole)

dohcsideSi

WThis is what I did but I haven't tried it yet as I don't have a distribution block :/

I just took out the large alternator wire that goes to the fuse box and ran the alternator straight to the battery.


This will work right?



Edit to add: could I run a cable directly to the starter before the switch and only run the power feed to the fuse box? Would this be legal?

drmix

Is your battery relocated to the back? Will the switch be located to the back? It looks like it would work but if your switch and battery is in the back there will be a few large cables that youll have to run all the way back. You also need to add fuses just in case there is a short anywhere.

dohcsideSi

Drmix my battery is under the front bumper, one of the reasons I don't want to add any more heavy 0 gauge wire.

Funny I was just looking at your signature, I have a 96 integra ls with a turbo 01 gsr swap that dynoed 427whp. We backed it off a little since the motor was bone stock with unknown mileage.

rudebwoy

iTrader: (1)

as I am looking at all these Diagram every time this subject came up people are complicating the whole idea and functionality of the system. The only thing you need to kill is the power from the battery and the alternator. How you do this is simple no matter where your battery is mounted, mine is in the trunk.

-one heavy gauge wire from positive side of the switch to a junction or distribution block. (I use a jump start terminal as my distribution point).

- connect the other side of the switch to the battery

-Run a wire from the distribution point to the starter.

-run another wire from the distribution point to the "stock" fuse box just as if you were running it if the battery was in the original location.

now you have a funtioning system that will only kill power to the battery, noticed I haven't said anything about the alternator.

the only way you will kill the engine and all power to the car is:

- run an additional wire from the positive terminal of the battery BEFORE the switch directly to the alternator.

this way when the car is running, if you turn off the switch, the car will die, this is the purpose of running a kill switch.

this works with a 2 pole switch.

a1320addict

iTrader: (1)

This has been covered before, many times.

rudebwoy

iTrader: (1)

That still won't work. a1320addict, the switch will kill the battery but what will kill the alternator? what if I tell you that after the car has been started you can remove the battery from the car and the car will still continue running with the alternator.

a1320addict

iTrader: (1)

Then I would tell you that you are wrong in assuming this diagram is incorrect.

Following the diagram:
-The switch will control the solid state relay, either closing or opening the circuit which will allow battery voltage to reach your cabin side junction stud > power distribution to your components. IF the car is still using an unmodified alternator, the alternator's exciter 12V will also be off of this distribution point.
-The alternator's output pole is on the IN side of the solid state relay, meaning that if the switch if OFF the alternator is now removed from the power distribution of the car - it will feed back to the battery, which in turn is also cutoff from supplying power to the car's electrical system.
-If the battery is suddenly removed from the car and the cutoff switch has not been thrown from on to off, than yes the alternator will continue it's power output. The purpose of the cutoff switch is to REMOVE power, not sit there unused while you tinker around removing a battery to showcase how an alternator works. In turn, if the cutoff switch is thrown - an unmodified alternator will lose it's excitation 12V.

Kevinio

If you cut off the ground you still will have potential differences between parts that could cause sparks. I never understand why people use a switch only for regulations, and not for their own safety.

rudebwoy

iTrader: (1)

your method will work but the idea is to completely kill all power starting at the battery.

Zubaltec

iTrader: (1)

If you have to install a battery cut off switch in your race car because of rules. Lets follow the rule set up by the body that governs the tracks we race on.

Read this from the NHRA rule book. I'm sure the IHRA rule book is similar.


8:4 MASTER CUTOFF
Mandatory when battery is relocated, or as outlined in Class
Requirements. An electrical power cutoff switch (one only) must be
installed on the rearmost part of each vehicle and be easily
accessible from outside the car body. This cutoff switch must be
connected to the positive side of the electrical system and must
stop all electrical functions including magneto ignition. The off
position must be clearly indicated with the word “OFF.” If switch is
“push/pull” type, “push” must be the action for shutting off the
electrical system, “pull” to turn it on. Any rods or cables used to
activate the switch must be minimum 1/8-inch diameter. Plastic or
keyed switches prohibited. Switches and/or controls must be
located behind rear wheels on rear-engine dragsters.

a1320addict

iTrader: (1)

The circuit breaker and solid state should be placed as close to battery positive as possible - reducing the amount of 'live' cable. Power will be removed starting as close to 6" of the battery - look at the diagram!

I agree, I know the rule - and using a solid state relay or battery isolator will both pass tech. If you followed the rule as they word it, you would actually be running BAT + cable to rear chassis - which is a disaster waiting to happen. But the rule also states that only one switch may be on the car at the rearmost panel, what happens in the event that the driver wants a cabin mounted cutoff switch as well in series? According to the rule, that's not allowed.

civic-steve-94

Just run an 80amp in line fuse from alternator to battery positive then from there to post one of two post switch then run post two to fuse block. I race circle track also and that is how we wire them up and it kills the car immediately