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ted1922

safety - battery cut off switch

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Some more thoughts on electron flow....Welding! We clamp a ground cable to a metal object. Then we control volts and electron flow from the tip of the welding gun, to the metal and back to the ground wire. Again, electrons moving so fast that they  melt metal.  We literally melt the metal pieces together using electron flow. Thicker metal needs more amps. We can only get so many amps from a 120v home welder. So we can only weld metal that is thin. Car body panels are thin. So these 120v welders work pretty well for autobody work. If we need to weld thicker metal plate we need more electron flow. So we up it to two or three phase 240V power. Now we’re talking! We can melt thicker metal now and join it together. 

 

Electron theory is just that. A theory. We can't really see it and touch it. We can measure it. We can control it and make it do things for us. It’s there. We sure can feel it when it goes through us. Ouch.  

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OY. On a pre computer car disconnect whichever is easiest, it does not really matter, either will open the circuit.

On a computer car always disconnect the negative first and reconnect last. Otherwise odd codes may set.

With air bags always wait about 20 minutes from disconnect to working, caps take that long to discharge.

DO NOT disconnect a battery with the engine running unless emergency. Have seen 200v spikes on sudden disconnect.

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4 hours ago, STEVE POLLARD said:

For winter storage, I've been disconnecting the positive terminal on the battery,

 

OK, for safety, always disconnect the terminal that is connected to chassis.  Why is this safer? Because when you are handling the wrench to loosen the nut on the terminal (unless you are like me and leave the terminal loose so you can twist it off without tools in an emergency...😉) the wrench my touch the terminal you  are disconnecting and the chassis at the same time, making big sprk/melt tool/burn hand/start fire issues. Just always disconnect the terminal connected to chassis first. It is in all the shop manuals!

4 hours ago, TerryB said:

If you disconnect just the NEG thermal on the battery (on a NEG ground car) there are ways that under the wrong circumstances an alternate path to ground can be established and harm done.  

 

OK, give me an example of how can just disconnecting one battery terminal (the one connected to chassis) can have an alternate path to ground? Maybe if the cat drops a wrench across the battery terminal and the chassis when you aren't looking?🙄 Of course, that would only leave the battery in the circuit, what harm would be caused? Much worse if the cat dropped the wrench from the disconnected non chassis connected terminal to the chassis, that would be a short/sparks/melted parts/fire/etc.......😵

 

Just disconnect the terminal connected to chassis and everything will be fine. On a negative ground car, that is the negative terminal. On a positive ground car, that is the positive terminal. 6 or 12 or 24 volts, makes no difference.

 

On a collector car, just a battery disconnect is needed. There is an ignition switch to turn the engine off! Kill switches are used in race applications, as they get into wrecks and course workers need to turn off wrecked cars when the driver is unable to turn the ignition switch off. This should not be an issue with collector cars (unless you are collecting race cars 😁). No need to mount an ugly switch on the rear of a Packard or Pierce Arrow and loose points in judging.....👍

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8 hours ago, Real Steel said:

 

This is my easy-to-reach switch mounted in my current unrestored daily driver, a 1930 Ford pickup...

 

8.JPG

Question:  May I ask where you found  the "cup" that the switch is mounted in on the floorboards - nice touch !  I need to do this exact thing in about a week.

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Hi Frank!  You must have seen my cat!  He was a trickery bugger for sure, one time he stole my keys and hid them for days!  Accidental connection through leakage paths from acid corrosion trails, sheet metal coming in contact with the battery, wrench or wire falls on battery and so on.   it would take some really odd combination of events to create a path to ground but odd things do happen!  Better to be over safe than playing detective.

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As a precaution when connecting the battery terminal look for sparking . If sparking is present then it is an indication of some instrument is on. A big spark might be the cut out switch is stuck closed. Safe way to protect the generator is to use a diode inline.  

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12 hours ago, John_Mereness said:

Question:  May I ask where you found  the "cup" that the switch is mounted in on the floorboards - nice touch !  I need to do this exact thing in about a week.

Hi John,

I replied to your PM with the info you requested.

If anyone else would like more info about this switch mounting method, I can post some photos in a new thread (I don't want to hijack this thread).

Alex

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On 10/13/2019 at 5:35 PM, 1937hd45 said:

Wonder how all the professional car haulers handle this problem with six cars on their way to and from Pebble Beach and other points during the year? Bob 

 

 

They usually don’t mess with the car, if it has a cutoff they only use it if you request it.

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I have cut offs in all my car and I put fuse blocks in also.  Since I rewire all my cars it is easy to install fuse blocks and fuse the important circuits.  I used to get them from Radio Shack but the last one I had to but on line.  I also put in fuel shut offs for leaking carbs.

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I disconnect the negative battery cable as soon my car gets in the garage at home or once it's in the trailer.  No battery drain and no chance of a fire :)

 

 

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7 minutes ago, amxdreamer said:

I disconnect the negative battery cable as soon my car gets in the garage at home or once it's in the trailer.  No battery drain and no chance of a fire :)

 

 

X 2 on the neg terminal disconnect.

 

Mike in Colorado

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17 hours ago, jan arnett (2) said:

I have cut offs in all my car and I put fuse blocks in also.  Since I rewire all my cars it is easy to install fuse blocks and fuse the important circuits.  I used to get them from Radio Shack but the last one I had to but on line.  I also put in fuel shut offs for leaking carbs.

 Marine suppliers, such as Jamestown Distributors, sell fuse blocks in various sizes that look just like those used in the late 1920's and 1930's. They hold the common glass tube "buss" type fuses.

 

https://www.jamestowndistributors.com/userportal/show_product.do?pid=12253

 

Paul

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