« previous next »
Pages: 1 [2] 3 4 5   Go Down

Author Topic: Battery cut-off  (Read 14171 times)

0 Members and 1 Guest are viewing this topic.

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Battery cut-off
« Reply #15 on: May 09, 2009, 10:29:06 AM »
NHRA REQUIRES it to be in the correct place. The POSITIVE cable .YOu Ozzies are just plain backwards .Really I want to SEE where any sanctioning body wants it on the negative side.Makes no sense to me.
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline Jerry

  • Sr. Member
  • ***
  • Posts: 271
Re: Battery cut-off
« Reply #16 on: May 09, 2009, 10:39:53 AM »
I am just not seeing the benefit of putting the cutoff on the neg cable. The pos side you have NO chance of shorts.

I just went and looked at the manaul My manaul for the motor says connect the pos first then neg when disconnecting neg cable first then pos. The motor is and efi so am guessing that has something to do with the computer.

I am now leaning toward one on neg and one on the pos, so i donot have and issue with the computer.

I JUST DO NOT KNOW WHAT TO DO... ??? ??? ???
Logged

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Battery cut-off
« Reply #17 on: May 09, 2009, 10:52:29 AM »
Proper procedure IS to disconnect the negative cable FIRST to prevent spark. That applies to a terminal connection at the battery. Batteries off gas and potentially COULD blow up .Not likely tho. For the electronics always disconnect the negative FIRST.  For ultimate safety in the event of an accident though the switch should be on the positive side. AS said earlier that prevents ANY current flow in the system anywhere. Any decent quality 12V cutoff switch is well enough enclosed to not be an explosion hazard 99% of the time. TRhere ARE some cheapo POS cutoff switches that are exposed and IMO should NOT be used .
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Battery cut-off
« Reply #18 on: May 09, 2009, 10:54:35 AM »
Oh and it's highly unlikely there is any harm to the electronics by shutting off the power on the positive side when the car is shutdown.Possible but unlikely. Different story if circuit is interrupted while car is running.
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline Engineer

  • Inquisitor
  • Global Moderator
  • *
  • Posts: 2657
Re: Battery cut-off
« Reply #19 on: May 09, 2009, 11:17:24 AM »
Quote from: Masterfabr on May 09, 2009, 10:52:29 AM
Proper procedure IS to disconnect the negative cable FIRST to prevent spark. That applies to a terminal connection at the battery. Batteries off gas and potentially COULD blow up .Not likely tho. For the electronics always disconnect the negative FIRST.  For ultimate safety in the event of an accident though the switch should be on the positive side. AS said earlier that prevents ANY current flow in the system anywhere. Any decent quality 12V cutoff switch is well enough enclosed to not be an explosion hazard 99% of the time. TRhere ARE some cheapo POS cutoff switches that are exposed and IMO should NOT be used .

The logic is starting to get a little bit twisted up there Fabr.

I believe for the same reason that they want the negative disconnected first and reconnected last is the very reason that "down under" they put the switch on the negative side.  Lets face it, both ways work.  And once disconnected with either method, you still have a 6" wire and a terminal that are hazardous if you drop a wrench on a bare spot.

With today's FI engines, I would be inclined to go on the negative side.

Going on the negative side allso eliminates the big NHRA problem of an alternator backfeeding the circuit and allowing a runnaway engine to continue to run.  With the cuttoff on the positive side, you must run the alternator wire directly back to the battery, or through a secondary switch, or it will continue to feed the circuit even after the switch is turned off, and allow the motor to continue running.

It is a good idea to test the switch to see if it kills the motor.
Logged

Offline Jerry

  • Sr. Member
  • ***
  • Posts: 271
Re: Battery cut-off
« Reply #20 on: May 09, 2009, 11:22:59 AM »
The cheapo switch you are talking, meaning the switch mechizm is expose. Thus allowinga spark correct
Logged

Offline Engineer

  • Inquisitor
  • Global Moderator
  • *
  • Posts: 2657
Re: Battery cut-off
« Reply #21 on: May 09, 2009, 11:27:01 AM »
The contacts are exposed allowing an open spark that could ignite fuel, etc.
Logged

trojan

  • Guest
Re: Battery cut-off
« Reply #22 on: May 09, 2009, 12:05:08 PM »
um...... I understand it's BOTH. not just negative. sorry if I implied it was just neg...

Why negative? Neg is sometimes erroneously referred to as ground, implying it is at the same electrical potential as the dirt-ground or Zero Volts. that is a very common misconception. With a 12v car battery, there can be as much as 20V of difference between the dirt and the negative rail... yes it can also be at 0V but there's no way to be sure without connecting the neg to dirt.
« Last Edit: May 09, 2009, 12:08:16 PM by trojan »
Logged

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Battery cut-off
« Reply #23 on: May 09, 2009, 12:12:55 PM »
Ahhhh,now that makes sense.
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

trojan

  • Guest
Re: Battery cut-off
« Reply #24 on: May 09, 2009, 12:30:34 PM »
Logged

artie on edge

  • Guest
Re: Battery cut-off
« Reply #25 on: May 09, 2009, 03:54:05 PM »
Quote from: trojan on May 09, 2009, 12:30:34 PM
As far as I know they must use a 4 pole switch. Artie?

http://www.gmpracingproducts.com.au/car-setup-equipment/switch-panel-switch-4-pole-battery-switch.php

Troj, the actual type os switch isnt stipulated BUT common sense would dictate a 4 pole for obvious reasons.

Ive never heard so much tripe in my life Fabr...stop and think about it for a moment...

On a negative earth chassis...the entire frame is part of the circuit.... Simply disconnecting the battery at the postive terminal leaves it open to accidental short circuits. Any body work or barwork near the positive terminal can potentialy SHORT out. By disconnecting the negative and removing current from teh chassis th eonly short that can now occur is directly across the terminals. Limiting the possibility (not ELIMINATING it though).

No one mentioned electronics or current flow, that all came from your misunderstanding of the issue. Your thinking is also a little flawed in this area, when using jumper leads always disconnect the earth lead first because you DIDNT put it on the battery, its on a good earth on th eengine somewhere, so when it sparks it wont cause the gas produced by the battery (Hydrogen) to ignite... Disconnecting th eneg at the battery to stop sparks simply will not work.... so what if teh spark jumps FROM or TO the terminal (the difference between pos or neg disconnect), it will still ignite the gas!

This regulation is about limiting possible damage or fire in teh case of an accident.

Now im off to golf you guys are carzy.. ;D
Logged

SPEC

  • Guest
Re: Battery cut-off
« Reply #26 on: May 09, 2009, 04:01:17 PM »
 ;D
Keep your shirt on
 8)
Logged

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Battery cut-off
« Reply #27 on: May 09, 2009, 04:41:19 PM »
Quote from: Artie on edge on May 09, 2009, 03:54:05 PM
Troj, the actual type os switch isnt stipulated BUT common sense would dictate a 4 pole for obvious reasons.

Ive never heard so much tripe in my life Fabr...stop and think about it for a moment...

On a negative earth chassis...the entire frame is part of the circuit.... Simply disconnecting the battery at the postive terminal leaves it open to accidental short circuits. Any body work or barwork near the positive terminal can potentialy SHORT out. By disconnecting the negative and removing current from teh chassis th eonly short that can now occur is directly across the terminals. Limiting the possibility (not ELIMINATING it though).

No one mentioned electronics or current flow, that all came from your misunderstanding of the issue. Your thinking is also a little flawed in this area, when using jumper leads always disconnect the earth lead first because you DIDNT put it on the battery, its on a good earth on th eengine somewhere, so when it sparks it wont cause the gas produced by the battery (Hydrogen) to ignite... Disconnecting th eneg at the battery to stop sparks simply will not work.... so what if teh spark jumps FROM or TO the terminal (the difference between pos or neg disconnect), it will still ignite the gas!

This regulation is about limiting possible damage or fire in teh case of an accident.

Now im off to golf you guys are carzy.. ;D
Speaking of tripe.Reread your post.
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Battery cut-off
« Reply #28 on: May 09, 2009, 04:44:10 PM »
The reason you put jumper cable negative on the engine is to prevent the majority of the jump current from going into the battery and absorbing much of it before it reaches the starter.That enables the starter to receive full amps from the jumper vehicle. The reason a battery is connected positive first and negative is always removed first is to prevent a spark but if under enough load-such as a direct short-it can still spark. The reality is that if you guys will stop and THINK for  bit it really doesn't matter which is disconnected so long as the alternator is wired properly-charging the battery only and not energizing the electrical system directly. Otherwise it makes no difference at all. I PREFER to isolate the positive . Also the talk about ground and earth is irrelevant in a car.Ground is ground since the battery is it's own "earth". Sheesh.
« Last Edit: May 09, 2009, 04:54:48 PM by Masterfabr »
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Battery cut-off
« Reply #29 on: May 09, 2009, 04:56:25 PM »
Quote from: Artie on edge on May 09, 2009, 03:54:05 PM
Troj, the actual type os switch isnt stipulated BUT common sense would dictate a 4 pole for obvious reasons.

Ive never heard so much tripe in my life Fabr...stop and think about it for a moment...

On a negative earth chassis...the entire frame is part of the circuit.... Simply disconnecting the battery at the postive terminal leaves it open to accidental short circuits. Any body work or barwork near the positive terminal can potentialy SHORT out. By disconnecting the negative and removing current from teh chassis th eonly short that can now occur is directly across the terminals. Limiting the possibility (not ELIMINATING it though).

No one mentioned electronics or current flow, that all came from your misunderstanding of the issue. Your thinking is also a little flawed in this area, when using jumper leads always disconnect the earth lead first because you DIDNT put it on the battery, its on a good earth on th eengine somewhere, so when it sparks it wont cause the gas produced by the battery (Hydrogen) to ignite... Disconnecting th eneg at the battery to stop sparks simply will not work.... so what if teh spark jumps FROM or TO the terminal (the difference between pos or neg disconnect), it will still ignite the gas!

This regulation is about limiting possible damage or fire in teh case of an accident.

Now im off to golf you guys are carzy.. ;D
Ummmm,yes they did.Read the whole thread  next time artie. Reply # 16.
« Last Edit: May 09, 2009, 04:57:58 PM by Masterfabr »
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"
Pages: 1 [2] 3 4 5   Go Up
« previous next »
 
SimplePortal 2.3.7 © 2008-2024, SimplePortal