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Remote Master Disconnect Switch/Relay


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#1 bjhines

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Posted 31 December 2007 - 08:10 PM

OK, So I need a master battery shutoff for the race car. I would appreciate anyone who can chime in on this.


I have seen quite a few hack jobs in this area. It seems that the old positive battery kill switch will not "cut it" in a modern car.

I have been looking into the remote/relay disconnect switches available through a variety of retailers. These things are expensive, and they are often incomplete.

I need to shut off the battery and the alternator power circuits without damaging either one. I am also concerned with any diode or resistors that should be included in the disconnect system to prevent alternator damage.




I seems to me that a pair of starter relays(one for batt. and one for alternator) and some mushroom cap emergency stop buttons are all that I need to cheaply shutoff my car's electrical system.
Why spend $100s on the store kits.
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#2 Tony D

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Posted 31 December 2007 - 11:36 PM

It cost us $15.99 for a master disconnect switch...same one everybody else used. Ran ALL grounds to the switch, and then to the negative post of the battery. If there is no ground, postive has no place to supply electrons to the backside of the battery.

A $2 6A Capacity Diode (rectifier) on the "L" terminal on the alternator (if I recall correctly, it's the one that comes from the ignition hot, not the sensing line.) to prevent reverse-feeding the circuits in the car so the dedicated ignition cutoffswitch didn't keep the car running after it was switched off.

All power fed in to the car's electrical circuits went through a master cutoff 'push to open' 75 Amp switch closest to the driver that cost $7.99. If you pushed it, it killed the car, period. If you opened the key switch on the negative terminal of the battery you killed the car, period.

I have heard you 'need' to have those dual-circuit disconnects to work with alternators, but nobody can tell me what kind of 'damage' will occur using the ground-depriving scenario I employed. Even an alternator can not make power if it's not grounded. Even if you think 'island mode' if the battery is disonnected at the negative terminal, and all your grounds go there (even if through the chassis, as long as the chassis grounds all are isolated from the battery ground terminal) it will not keep excitation as the field circuit opens.

On the Lemons Car, 'cheap' was a prime consideration, and it wasn't until after I built the damn panel did I find out they did not require an external power kill switch (like everybody else on the face of the planet who sanctions races does!) Oh well, it was a learning experience.

#3 bjhines

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Posted 01 January 2008 - 08:14 AM

I have been doing some reading.

Alternator Tech:
http://www.rowand.ne...ratorTheory.htm

http://www.madelectr...owitworks.shtml

http://www.madelectr...delcoremy.shtml


Remote cutoff switch tech:

http://www.pezzano.c.../batterycutoff/#







There is a difference between an Alternator Disconnect Relay, and an Alternator Protection Relay. It seems that the Alternator disconnect may be redundant depending on where you actually disconnect the system.



I am interested in the remote operated "Kill Relay". This device will allow several remote switches to kill the system.

This $200 relay duplicates the function of the available kill switches with protection circuits.
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Here is a typical wiring diagram for the key operated switches everyone uses.
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The operation of the devices is the same. The kill system interrupts the battery power and kills the ignition circuit at the coil to eliminate alternator-feedback run-on. The same switch also grounds the alternator charge circuit through a resistor when "killed".




It seems that the function of the alternator protection contacts are to keep the alternator from "dead heading" into an open circuit from a fully operating condition. The field and stator coils must "collapse" AND the alternator continues to turn for a moment before the engine stalls. This can create a voltage spike and damage modern semiconductor regulators. The alternator protection cicuit is not in series with the alternator to Battery wire. It is simply a shunt to ground through a resistor when the system is Killed. It does not have to withstand constant high current operation.

The alternator protection contacts are normally closed.
This means that...
When the Kill switch is ON the alternator protection contacts are OFF.
When the kill switch is OFF the alternator protection contacts are ON.
They shunt current from the Alternator Batt. terminal to ground through a 3ohm 15watt resistor when the switch is killed.
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#4 evtech

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Posted 01 January 2008 - 08:51 AM

Hi

Over here in the UK we have to comply with the RAC 'blue book' of rules for motorsports. This link is to a UK supplier of Autolec master switches, easy wire and fool proof,

http://www.demon-twe...&pcode=LEMMW002

To make it 'remote' you either mount it externally on the car (front windscreen/scuttle panel) or as I've done on many occasions fit it in the car and run a pull cable (like a choke pull) through the car from the outside and fit the switch in easy reach of the driver, also it has to be marked wit a waring sign because rally cars tend to have these mounted next to the fire extinguisher system.

Happy New Year

Nigel
Never drive faster than your Angels can fly :redface:

#5 bjhines

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Posted 01 January 2008 - 10:05 PM

I installed a demo copy of SMART DRAW and got to work.


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KILL SYSTEM COMPONENTS:
The START and KILL relays are starter solenoids. The KILL solenoid is rated for continuous operation. The starter relay is a cheap FORD unit.
The Alternator protection relay and the IGN KILL relay are BOSCH units. Notice that the Alternator is wired to the NC terminal. The IGN KILL relay is wired to the NO terminal.

The KILL switch(s) are 40mm Mushroom button, push to kill, twist lock ON switches. Multiple switches can be wired in series. Opening any switches' contacts kills the system.

FUSING:
I have fused the important points in the system. 80A fuseable link at the alternator. 80A fuseable link at the solenoids(near the battery). The BOSCH relay coils are fused with 5A. The starter-mounted solenoid jumper is a 40A fuseable link.

REAR BATTERY:
The battery is rear mounted so there are some long runs of cables. I decided to use a remote starter solenoid to prevent the heavy guage, battery-to-starter cable from being live at all times. With the rear mounted starter solenoid, the large cable will only be hot when the IGN switch is in the START position. I will use a 40A fusable link as a jumper between the starter cable and the starter-mounted solenoid.

POWER JUNCTIONS:
The main junction block will be located near the battery and solenoids. I will attach all of the vehicle power systems to this junction at the back of the car. I will reroute the original fuse panel power wire to the rear junction, I will add an additional front fuse/relay block, and a rear mounted fuse/relay block.

ALTERNATOR:
I will be using a 3 wire DELCO 12SI alternator. I decided to use the CHG light, and the SENSE wires in their proper configuration.
I will run the sense wire all the way back to the main/rear junction block. This will ensure that the vehicle systems receive a properly regulated supply voltage.

WIRE GUAGES:
The curved red battery cables are all 1/0 guage. The battery ground cable is a short 1/0 guage bolted to chassis ground. The curved red/white power cables are all 8 guage. All other wires are 16 guage. I will add large ground straps to the starter/engine block to ensure a good chassis ground. The entire chassis has been seam welded and there are heavy guage subframe connectors that should make for a better than average chassis ground system.

MOUNTING POSITIONS:
The battery, the solenoids, and the junction block will be mounted behind the passenger seat. I have unwrapped the entire harness so I am pulling out wires that are no longer needed and I am adding less than 2' to the original factory fuse panel supply wire.

ADDITIONAL CIRCUITS:
The AUX FRONT fuse/relay panel will accomodate the headlight relays, cooling fan relays, and ignition power relay(not the ignition kill relay)

The AUX REAR fuse/relay panel will accomodate the dual fuel pump relays, differential cooler pump relay, differential cooling fan relay, as well as the fuel level sender power circuit, onboard camera/D.A. power, and my cool-suit system relay.
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#6 bjhines

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Posted 02 January 2008 - 09:15 AM

I ordered the emergency stop switches I will be using.

http://web2.automati...ations/E22LPB2B

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#7 bjhines

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Posted 04 January 2008 - 08:39 AM

Ha,

It seems that many sanctioning bodies require that the alternator wire is connected to the battery side of the kill switch. This ensures that the alternator cannot continue to run the electrical system with the system killed.

I have shown my diagram with the alternator wire on the car side of the kill switch.

I am definitely going to leave enough extra wire to allow the system to be set up EITHER WAY, depending on what tech inspectors decide about my system.

I prefer the way I have shown in my diagram. The reasoning is that the alternator wire runs the length of the car from the rear battery/solenoid tray to the alternator +post.
If I wire the alternator directly to the BATT+ side of the kill switch then there is still a LIVE wire running the length of the car even after the switch is KILLED.
In my diagram the alternator is wired to the CAR side of the kill switch. The Alternator wire is removed from the battery when the system is killed. The tendancy for the system to "run on" is eliminated by the IGN KILL relay. This means that the system cannot continue to run and the alternator wire goes stone-cold-dead as soon as the engine stops turning. This also eliminates the need to fuse BOTH ends of the alternator wire.




Another issue that crops up comes from the remote starter solenoid I am using to ensure that the 2g starter wire is dead except when it is starting the engine. I show a jumper between the starter BATT wire and the starter-mounted solenoid. This would work fine in a factory style starter. The problem comes from the fact that I am using a permanent magnet starter motor.
The permanent magnet motors can generate electricity if the pinion does not instantly/completely disengage. The electricy generated by the starter motor will energize the jumpered starter solenoid and KEEP the starter engaged until the engine overrunns it enough to kick the pinion off the ring gear. This is noisey and damaging to the starter.
The fix for this is to use the KEYED start signal wire to engage both the rear-remote solenoid AND the starter mounted solenoid(without a jumper). Unfortunately the starter signal wire is heavily taxed in the factory system. Forcing this wire to run TWO high current solenoids will not be smart.
The answer is to add another BOSCH 30A relay near the starter to take some of the load off the starter signal wire and get rid of the starter jumper in my diagram.

DAMN this gets complicated quickly.
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#8 heavy85

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Posted 04 January 2008 - 05:30 PM

DAMN this gets complicated quickly.


So I have to ask why dont you just use the simple $50 switch from Pegasus in your #3 post? All this remote solenoids and extra relays and stuff just seems to add unneccessary complexity and potential unreliability.

Cameron

#9 Six_Shooter

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Posted 04 January 2008 - 06:05 PM

Taylor has a 4 post main disconnect switch, that will kill both the main battery feed to the vehcile and the Alternator charge lead in the same switch.

Part# 1033
http://www.taylorver...orcatalog37.pdf

I'll have to read some of the links in this thread, but I have not heard of any problems with shutting off the alternator output through a disconnect switch, or even when using the two post switch with the charge lead wired to the battery side of the switch.

The need to use the switch in this instance is very low and only when something else has gone terribly wrong, such as hitting the wall, at which point I think the alt will be the least of your worries. ;)
I could see how this may be a concern during the mandatory test at almost every tech in, especially at a sanctioned event.

Also all rules that I have read state thet the positive side of the electrical system must be the switched side, not the negative. NHRA and IHRA for sure, it's been a while since I've seen any SCCA rules though, among others.

#10 Dave

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Posted 04 January 2008 - 10:19 PM

Ha,
Another issue that crops up comes from the remote starter solenoid I am using to ensure that the 2g starter wire is dead except when it is starting the engine. I show a jumper between the starter BATT wire and the starter-mounted solenoid. This would work fine in a factory style starter. The problem comes from the fact that I am using a permanent magnet starter motor.
The permanent magnet motors can generate electricity if the pinion does not instantly/completely disengage. The electricy generated by the starter motor will energize the jumpered starter solenoid and KEEP the starter engaged until the engine overrunns it enough to kick the pinion off the ring gear. This is noisey and damaging to the starter.
The fix for this is to use the KEYED start signal wire to engage both the rear-remote solenoid AND the starter mounted solenoid(without a jumper). Unfortunately the starter signal wire is heavily taxed in the factory system. Forcing this wire to run TWO high current solenoids will not be smart.
The answer is to add another BOSCH 30A relay near the starter to take some of the load off the starter signal wire and get rid of the starter jumper in my diagram.


Remove that jumpered starter solenoid wire and use a Ford starter solenoid that has the 2 connections one being for the old point type ignitions. Use that (I) terminal that would normally bypass the ballast resistor in start position to trigger the solenoid on the starter. This way there is not a connection to let the starter run on as described above.
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#11 bjhines

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Posted 04 January 2008 - 11:26 PM

Thanks for the input on this guys.

I have come to realize that there are a lot of ways to do this. There are a lot of little issues that crop up.

Dave,
The "I" terminal is beautifully simple. Thanks for the idea!
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#12 bjhines

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Posted 04 January 2008 - 11:28 PM

The main components of this rig are mounted and fed. It weighs 3lbs-3.2oz.

I have $200 invested in this thing including all of the heavy guage wires to all fuse panels, alternator, and battery.
That beats the $200 kill relay offered to Porsche and BMW owners. I have more functionality and nicer buttons to push.
I have remote start, main circuit breaker, rear battery relocation, and a fuse panel thrown in for the same money. I can easily move the alternator feed to several different points depending on what tech officials require.


The mounting frame is a battery mount for an Odyssey PC-680 motorcycle battery. 680 cranking amps/1200amps shorted, with a 17-Ah capacity.

The large solenoid is the kill relay. It is a contuinuous duty type with a 16 ohm coil($50).
The small solenoid is the starter relay. It is for intermittant duty with a 3 ohm coil($10).
The circuit breaker is a Buss CB185-150Amp($27).
The small fuse panel is a Buss 6-circuit rated at 30amps per circuit, 150amps at the stud($15)
The 4guage wire is a Rockford Fosgate amplifier install kit($70). It was the best quality I could find without a lot of other junk in the box.
The starter cable is 2 guage that I found for $1.88 per foot. It is tough jacketed and flexible. The grounds are the same stuff.
The silver 6 guage wire is silver plated fine strand wire with a TOUGH thin-walled jacket(more leftovers). I will only use it inside the car.
I am sheething the cables in braided nylon protective sleeving. It is tough stuff and willl bundle them nicely(~$90 roll). I have a roll left over from another job that is paid for and collecting dust.
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Flush mounted screws to prevent damage to the battery.
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I had to make a bunch of solder lugs to suit the 4g cable and the various sized terminal studs.
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#13 Dave

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Posted 05 January 2008 - 01:24 AM

If you look at the solenoid/relay pictured you will see a diode between the (+) and (-) coil connections. This is a fly back diode also can be called a clamping diode. There is a inductive spike when the coil voltage is removed that causes arcing at the switch that runs the solenoid/relay and spikes into the cars electrical system. This diode takes the spike to ground. The switch points don't arc with the diode and it protects sensitive electronics in the car. Some relays come with clamping diodes but I don't think the ones your using have them.

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#14 bjhines

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Posted 05 January 2008 - 07:26 AM

Thanks Dave,

The STARTER-solenoid and the small Bosch relays have them built in. The Constant-duty KILL-solenoid does not have a diode. I have some heavy duty 30V rectifier diodes I will install in several places when the small guage wiring is added.
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#15 bjhines

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Posted 05 January 2008 - 11:06 AM

I have started building the 2g battery cables. The wire has a tough clear insulation jacket. I could not get red or black at a good price.

I am using heavy copper lugs. I Have drilled holes in the wells in the lugs to allow soldering from the inside. This ensures that the cable is well soldered and there is no contamination of the battery cable with solder or flux. I have a 250W iron for stained glass work that evenly heats the lugs and the wire for a good solder joint with good wire flexibility at the terminal.

The ends are covered with high quality heat shrink tubing. Then I pull braided nylon sleeve over the wire from lug to lug. Then I use glue coated heavy wall heat shrink to permanently bond the braided sleeve to the ends of the wire.

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#16 bjhines

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Posted 05 January 2008 - 11:16 AM

Hehe.. A redneck way to check if there is a diode on your solenoids is to connect a 9v battery across the coil leads. then hold the wire ends with your fingers and make and break the contact with the battery.
If there is no clamping diode you will get a strong jolt from the coil every time you break the contact.
If there is a diode present then you will get no jolt.
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#17 Dave

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Posted 05 January 2008 - 12:49 PM

Thanks Dave,
The Constant duty solenoid and the small Bosch relays have them built in. The starter solenoid does not have a diode. I have some heavy duty 30V rectifier diodes I will install in several places when the small guage wiring is added.

I started out doing the battery disconnect center like yours but changed to a Intellitec latching relay for the battery disconnect instead of the continuous duty relay. The reason being that the continuous duty relay will always draw .75 amp to keep the battery connected. A latching relay only draws power momentarily to connect/disconnect the battery.

I have the battery disconnect center with fuses in the back of the Z like you are doing. In the disconnect center is also a Ford starter solenoid that supplies the starter power and starter solenoid power like I explained a couple posts back. I have a toggle switch mounted behind the rear licence plate that will disconnect the battery. All I do is remove the plate at the track to make it accessible. That is if I ever get there.

I also bought a Odyssey PC680 to use, but with its being only a 16 amp hour battery it will go dead in short order if anything is left on. I have a electric fan and water pump that will continue to run after the engine is shut down if the cooling temp is over 190 degrees. I have since switched a Exide equivalent to the Optima battery.
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#18 bjhines

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Posted 05 January 2008 - 02:37 PM

The only issue I have with the latching relay is one more mode of failsafe is lost. If damage occurs to the kill switch wiring then the relay cannot be switched OFF.

In the system I am using the switches are wired in series and if there is ANY damage to the switch wiring the system will disconnect automatically.

I was considering installing a rollover/impact safty switch in the system to further improve safety. That way if I am out cold the electrical system will be too.
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#19 Dave

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Posted 05 January 2008 - 03:21 PM

I was considering installing a rollover/impact safty switch in the system to further improve safety. That way if I am out cold the electrical system will be too.

I have a bunch of the inertia switches used for fuel pump shut off. I set up my Z to use one but have yet to connect it. I actually have 2 setup, one for the pump and the other for the relay center so the pump is double covered.

If your in need of a inertia switch PM me and I will fix you up.

These switches use a steel ball suspended between 2 magnets with a red reset button. I have mine attached to the drivers kick panel so its easy to reset.

When I was researching the use of relays the one thing I read is early failure is caused by contact arcing when there is a heavy load on them when they are disconnected.

My main battery disconnect only cuts the power to the cars electrical system. I did not run the starter solenoid supply through it.

I have a 8" 2/0 positive cable from the battery that feeds a buss in the battery center, from there the starter solenoid feeds the starter and the main disconnects feeds the car. My alternator output does go to the buss. When everything is off I have a live 7 amp fused line to the disconnect relay switches and a 100 amp breaker in the live line to the alternator. these are in the battery center also.

I was going to do the relay and resistor for the for the alternator but figured if one or the other went out went out I could lose a alternator.
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#20 Dave

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Posted 05 January 2008 - 07:08 PM

Thanks for the input on this guys.

I have come to realize that there are a lot of ways to do this. There are a lot of little issues that crop up.

Dave,
The "I" terminal is beautifully simple. Thanks for the idea!

When I did my battery control center I started with one from a RV and built it from there. The fuses set on a platform above the starter solenoid.The big relay is the battery disconnect and the small solenoid is a Ford type starter solenoid. On the left wall is the main breaker from the alternator output. In the right lower corner is a connection point for the power lead to the starter. The connection points on either side of the big relay are the battery lead and the main power to the cars electrical system. There are 2 small (gray) 30 amp breakers on the end plate that I can pull power from if I need to.

When the battery disconnect relay is off the 8" lead to the battery is live. The line to the alternator with the breaker in it and and a 7 amp fused control circuit to the large relay are also live. Once the power is cut at the battery control center the engine does stop but the alternator out put still makes it to the battery. I have a inerta switch that also stops the battery power if there is a impact. A toggle switch is used to turn on/off the large battery disconnect relay or reset it if its shut off by the inertia switch.

All this sets next to the battery so there are not any large hot battery cables running to conventional disconnect switches.

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