Battery Cut-Off Wiring?

Hey Grant,

This breaker idea seems pretty good. But do you carry a jumper for jumping around the breaker just in case? Breakers can fail, 'specially when they are subjected to a lot fo shock and vibration. This is just a suggestion.

Regards,
Mark B.


NoCoast Wrote:
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> In 2004 I went off thanks to a patch of glare ice
> and gravel tires in my rally car while driving
> through the mountains to a rally cross. A pole
> came under the bumper and took out a few
> components and shorted some wires to the ground.
> I was almost instantly on the master battery kill
> switch after the wreck, but still ended up having
> to replace a large amount of the wiring harness
> that had burnt.
>
> With my current setup, the short would have
> tripped the breaker on the battery ground and the
> harness would have probably survived.
>
> Grant Hughes
> www.nocoastmotorsports.net
> Denver, CO

You should also ask Grant the exact type/brand of breaker being used. AC breakers are significantly different than DC breakers, and there are a couple of types of DC breakers.

If the switch is close to the battery, I can't see much difference in + or -. We have done both; the only disadvantege I have seen in the - side is that the switch has some finite resistance, and the resistance to ground of the battery through a switch is not as low as with the switch in the + side. As a result, we have had some noise issues in the intercom in the - lead installation we did on one car.

From a wreck standpoint, maybe the best lead is the one that is shrotest from the battery to the switch. This minimizes the chance fo having a hard short in a wreck between the switch and the battery post. Just thinking out loud.

Regards,
Mark B.

mack73 Wrote:
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> Ok so I guess I'm back to my origional question:
> Switch the positive or negative?
>
> I would rather switch the negative for easy of
> wiring. Good, bad, indiferent?
>
> Grant: what size breaker do you have on the
> ground? 100? 150? 175? amps
>
> 94 Golf
> www.Mack73.com
>
>
>
> Edited 1 times. Last edit at Feb 27, 2009 by
> mack73.

Got a picture on my phone but having network issues getting it to myself. The idea is courtesy of Salta Motorsports who have done the same in about 10 other rally cars in Colorado and was used/tested in Mitch Williams cars all last year during the USRC, as well as many cars at Rally Colorado, Rally Idaho, and other Southwest Cup events.
It's a 150 amp and I got it direct from Salta. I did set it up so it's easy to bypass it if the breaker were to fail.

---

Grant Hughes

NoCoast Wrote:
-------------------------------------------------------
> Got a picture on my phone but having network
> issues getting it to myself. The idea is courtesy
> of Salta Motorsports who have done the same in
> about 10 other rally cars in Colorado and was
> used/tested in Mitch Williams cars all last year
> during the USRC, as well as many cars at Rally
> Colorado, Rally Idaho, and other Southwest Cup
> events.
> It's a 150 amp and I got it direct from Salta. I
> did set it up so it's easy to bypass it if the
> breaker were to fail.
>
> Grant Hughes
> www.nocoastmotorsports.net
> Denver, CO

That breaker idea is smart thinking 101.

---

Andrew M
Onterrible
30ish

Thanks guys.

I think I'm going to forget the master switch and stick a breaker on the ground. Everything that isn't running on the stock wiring (ECU, Lights, Fan, Fuel Pump) is going to be running through individual breakers anyways.

I'm looking at this breaker: (Bussman 150 amp.) http://www.keefeperformance.com/circuit_breakers.html

I'll keep a pre-terminated battery cable in the car to jump the breaker incase it fails.

---

-Jason

something like this?
http://www.hifisoundconnection.com/Shop/Control/Product/fp/vpid/1333043/vpcsid/0/SFV/30046

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Jon Burke - KI6LSW
Blog: http://psgrallywrx.blogspot.com/

Yeah, here's basically the one I used.
http://wiringproducts.com/index1.html

But whatever you do don't order it from these motherfuckers. $100 order of stuff never showed and unfortunately was during a really busy period for me and kept calling and sending emails with no response regarding my order and went beyond the chargeback date. I think someone said they got one at Autozone too.

RE: Breaker failure, quite a few options, but the easiest is to just bolt both onto one terminal if the breaker were to fail.

---

Grant Hughes

mack73 Wrote:
-------------------------------------------------------
> Thanks guys.
>
> I think I'm going to forget the master switch and
> stick a breaker on the ground. Everything that
> isn't running on the stock wiring (ECU, Lights,
> Fan, Fuel Pump) is going to be running through
> individual breakers anyways.
>
> I'm looking at this breaker: (Bussman 150 amp.)
>
> I'll keep a pre-terminated battery cable in the
> car to jump the breaker incase it fails.
>
> 94 Golf
> www.Mack73.com


Seems like a very good idea. Some thoughts: Look and heed any instructions for mounting on a metal surface or in clear air or whatever. This is a thermal only type of breaker so has a finite internal resistance and will produce some small degree of heat for its action' extranl haet sources can effect its trip point. The mfgr should give instructions on how to mount. I would not want a 'nuisance trip' on-stage at night when I had 6 100W Halogen lights going just becasue I mounted this on the floor where the exhaust could heat it, and it got just a bit too hot for a bit too long!

Regards,
Mark B.

So I don't see how the breaker on the negative is safe when compared to the positive source. Say if you have a wreck were the batteries negative post is grounded to the body or the wire from the negative post on the battery to the switch grounded to the body your negative switch is no useless in shutting off the car or isolating the battery from the electrical system.

Andrew_Frick Wrote:
-------------------------------------------------------
> So I don't see how the breaker on the negative is
> safe when compared to the positive source. Say if
> you have a wreck were the batteries negative post
> is grounded to the body or the wire from the
> negative post on the battery to the switch
> grounded to the body your negative switch is no
> useless in shutting off the car or isolating the
> battery from the electrical system.

Yep afterall where does neg on battery go?
Straight to the body. Thus it in essence IS the same as body.

Unless there's some massive load on, and neg is loose somewhere like in open, there isn't going to be any excitment if neg toughes.

+ on the other hand, yikes!
So i want to cut off + at the place lots of + energy is stored---the + terminal of the battery.

But what the fuck do I know?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

I know in my case the battery is right behind the codriver's seat where it's probably the most protected.

The switched positive has been in use for years and is probably great and many people who have had the negative breaker put in still are using a positive switch. I know in my case when I had a short, the breaker would have helped, the positive switch was too late, and that the switches are usually just an annoyance/scare/complication/added expense to me, but what do I know I'm only on my second rally car and have only been rallying for 5 years or so.

PS> Won't the ignition switch accomplish much of the same things as a master power switch?

---

Grant Hughes



Edited 1 time(s). Last edit at 03/02/2009 12:12PM by NoCoast.

good stuff, lots of options.

IIRC, there's no specific rule around having a manual electrical cutoff, is there? so its pretty much just dowhatchyalike?

---

Jon Burke - KI6LSW
Blog: http://psgrallywrx.blogspot.com/

Finally go the picture from my phone to here!

---

Grant Hughes

Andrew_Frick Wrote:
-------------------------------------------------------
> So I don't see how the breaker on the negative is
> safe when compared to the positive source. Say if
> you have a wreck were the batteries negative post
> is grounded to the body or the wire from the
> negative post on the battery to the switch
> grounded to the body your negative switch is no
> useless in shutting off the car or isolating the
> battery from the electrical system.


Well not really. The risk is the same if the switch was on the + or -

Since the voltage needs to flow in a circle, disrupting the path at any point (before or after the device) will result in the same event (electrons can't get from the + post on the battery to the - post on the battery). The only difference is where the electrons are held up: at the + switch or you guessed it, at the - switch.


So in your example: if switching positive, but the battery were to flop around and the + post or the wire leading from the battery to the master switch came in contact with the body = sparks of fun.

If the switch was on the negative and the battery were to flop around and the - post or the wire leading from the ground switch to the battery came in contact with the body = sparks of fun.

I understand what your getting at but if the - battery cable was removed from the battery and you touched a positive cable from the battery to the car, you don't get any sparks do you?

So which battery cable do you take off first when removing a battery

---

-Jason



Edited 1 time(s). Last edit at 03/03/2009 12:24PM by mack73.

The voltage on the negative side would be much lower. Low voltage = less chance of sparks.

---

Robert.

"You are way too normal to be on Rally Anarchy." Eddie Fiorelli.