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safety - battery cut off switch


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I know a lot of your vehicles have been restore to the original status when it came from the dealer, and you want to keep it that way.

for a safety issue I always in stall a battery cut switch on all my cars,  if you are storing your vehicle, or you are trailing it to a show, it is a good security device, and emergency you can shut of all power to your vehicle.

It is something to think about.

Here is some photos no one wants to see in there rear view mirror.

This was a big time show car.

zooot1.jpg

zoot2.jpg

zoot3.jpg

zoot4.jpg

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Just now, padgett said:

When installing a cut-off switch, also make sure you disable the generator/alternator.

Could you please explain why this should be done? I'll never understand electricity, and never read about the generator/alternator deal. Explaining the invisible is impossible, but please give it a try. Bob 

Edited by 1937hd45 (see edit history)
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Is easy, have been in the position where it was necessary following an incident to be able to kill a running engine. Just disconnecting the battery may not, need to disconnect the generator/alternator also. If going to do one, you should do the other.

 

If your only purpose is to disconnect the battery for storage then just a battery disconnect will work.

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I tend to use a cut off, (with a sidenote that there are plenty on the market not designed for high enough amps, so do your homework) = I had a few regulators fail on the 1930 Franklin over time and each time they took out a $600.00 generator rebuild (or the generator failed and ...,  when battery got low it allowed regulator to close or ...  - never could quite pinpoint the issue),  and as a result I just lost trust and started using cut-offs.

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58 minutes ago, padgett said:

Is easy, have been in the position where it was necessary following an incident to be able to kill a running engine. Just disconnecting the battery may not, need to disconnect the generator/alternator also. If going to do one, you should do the other.

 

If your only purpose is to disconnect the battery for storage then just a battery disconnect will work.

So there will be TWO switches, battery AND generator/alternator, were do you mount the G/A switch? 

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3 hours ago, padgett said:

If your only purpose is to disconnect the battery for storage then just a battery disconnect will work.

For winter storage, I've been disconnecting the positive terminal on the battery, then once a month, hook it up and attach the trickle charger, run the engine, then disconnect it again.... just wondering if both pos & neg terminals should be disconnected during storage ?

 

Thanks

 

Steve 

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I would think disconnecting the positive should be sufficient.  As long as the engine is not turning over there will be no voltage generated that can do harm.  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.  

 

The idea of a multi-pole switch makes perfect sense when the need to completely disconnect a running car is required.  As mentioned, a competition car would need to completely shut down the electric connections especially when an accident might have happened.

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25 minutes ago, STEVE POLLARD said:

For winter storage, I've been disconnecting the positive terminal on the battery, then once a month, hook it up and attach the trickle charger, run the engine, then disconnect it again.... just wondering if both pos & neg terminals should be disconnected during storage ?

 

Thanks

 

Steve 

 

If you are going to disconnect only one terminal, then ground(-ve) is the better one to disconnect. Having said that, nothing wrong with disconnecting the +ve terminal either.

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After a generator cut-out fire (right next to the carburetor) in my 1929 Hudson Coupe, I've installed a battery switch in every vintage vehicle that I've had since.  I strongly encourage my friends to do the same (right Matt?). 

 

To all the great folks here at the AACA, please do this small safety modification to protect your historic vehicle, and possibly your life.

 

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

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8.JPG

Edited by Real Steel (see edit history)
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Just now, maok said:

 

If you are going to disconnect only one terminal, then ground(-ve) is the better one to disconnect. Having said that, nothing wrong with disconnecting the +ve terminal either.

I'm 68 years old and ever time I read something about electricity I understand less and will die knowing NOTHING. Up to this point in my life there was POSITIVE with + sign, and NEGATIVE with a - sign. What is (-ve) and (+ev) ?

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5 minutes ago, maok said:

 

If you are going to disconnect only one terminal, then ground(-ve) is the better one to disconnect. Having said that, nothing wrong with disconnecting the +ve terminal either.

On a negative ground auto disconnecting the positive higher voltage terminal takes away the ability for electrons to flow.  With no push from the higher voltage no current can flow.  Disconnecting both terminals is the safest as is removing the battery altogether.

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7 minutes ago, 1937hd45 said:

Somebody must have car fire research information, wonder what are the most common causes? Wonder what lit the Packard in the hauler? Bob 

 

For 1930s and older vehicles, I do know that sticking contact points at the generator cut-out is not so unusual.  If the points remain closed after the motor is turned off, the battery will short right through the generator to ground.  A lot of current can pass through a 16G  wire, and a fire is very likely.  

 

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3 minutes ago, 1937hd45 said:

I'm 68 years old and ever time I read something about electricity I understand less and will die knowing NOTHING. Up to this point in my life there was POSITIVE with + sign, and NEGATIVE with a - sign. What is (-ve) and (+ev) ?

It’s UK English for voltage. All the same thing.

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16 minutes ago, TerryB said:

On a negative ground auto disconnecting the positive higher voltage terminal takes away the ability for electrons to flow.  With no push from the higher voltage no current can flow.  Disconnecting both terminals is the safest as is removing the battery altogether.

All set with my car batteries now - everything has been disconnected... electricity is where I lack in knowledge ( home & vehicles ) I know little, but not enough.... Thanks for the input !

 

Steve

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1 minute ago, 1937hd45 said:

Steve nobody understands less about electricity than I do. All my car projects are sold before any wire goes in. Bob 

Never like electricity Bob.... when I was in the fire service, one of my assistant fire chief's was a licensed electrician.... he handled all the electrical fire calls...  😉

 

Steve

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1 hour ago, TerryB said:

On a negative ground auto disconnecting the positive higher voltage terminal takes away the ability for electrons to flow.  With no push from the higher voltage no current can flow.  Disconnecting both terminals is the safest as is removing the battery altogether.

Every electrical discussion is good for one never before mentioned tid bit, Why is there more voltage on the positive side? If you remove a perfectly good battery from your car in the fall and it is dead in the spring, were did the electricity go? Bob 

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I’ll attempt to simplify car battery electricity. Just because it’s fun. 

This is for the folks who said they don’t understand electrical stuff. Here’s my simplified version. 

 

The battery has a chemical reaction going on inside it. All the positive charged electrons are connected to positive terminal post. All the negative charged electrons are attached to the negative post. Electrons don’t necessarily like to be separated, nor charged positive or negative. They like to be neutral.  If all the negative and positive electrons are allowed to mix together in a battery to us commoners, “it’s dead”. The electrical differential is gone. It makes no power to turn anything “on” any more. 

 

So back to the positive and negative electrons. They are dying to get together and will do so at the speed of light, at any opportunity. The negative electrons will rush over to join the positive electrons when a good pathway is provided. Try laying a steel wrench from one battery post, connected to another and you’ll see. Those darn electrons will move so fast and so furiously that they'll heat up the steel wrench and melt it! So we don’t do these things. We have learned to harness and control the mass flow of electrons. So in a car for example we hook up one battery terminal to the car frame. We call it ground. It’s not really ground. It’s a metal frame. Electrons move really well through metal. The other battery post we connect to various electrical loads to make them do work.  Then we connect the other side of the electrical load to the car frame. So we then have a complete circuit back to the battery. Electrons can flow from the battery, to the load, like a starter or head lamp, whatever, and make that item work, and then the electrons flow back to the other battery post, via the car frame. They’ll travel fast but we have designed things so that only so many electrons are needed, and can go through the electrical load and back to the battery. We control electrons and we measure them by reading amperes or “amps”. We can use resistance to slow down the flow of electrons (amps). Also smaller wires and smaller electrical motors too, for example will use less amps.  Only so many electrons can squeeze thru a small wire. If too many try to slam thru a small wire it’ll get hot and melt.  By using wires to control and direct the flow of rushing electrons we can move them safely. If we get a “ short”and too many electrons jump to ground via a “short-cut” back to the battery a fuse will melt, (if one is used in the circuit) Rendering the circuit dead. Then there’s no further electron flow.  However most old cars have too few or no fuses.  The old cloth wiring eventually erodes and turns to thread.  Wires that are not properly secured can vibrate and rub, then rub the outer insulation off, exposing the core wires.  Imagine that exposed wire, now touching the metal car frame, giving the moving electrons a free quick path back to the other battery post. Via the frame. Maybe no fuse is used. Now electrons are lovin’ life! Moving at will with no barriers or other restrictions,  back to the other battery post. Moving at the speed of light, these pesky electrons create heat, fast. Real fast. Wire insulation then melts & catches on fire. With no fuse to stop the flow,  flames quickly appear. Easily engulfing your old car as it burns to the ground. 

 

If you install a battery shut-off switch it has the same effect as removing 1 battery cable from the battery post. You stop the path of electron flow. Nowhere for them to go. No possible short to create a fire. 

 

Stay tuned for a watered down story about 6v vs 12v versus 24v systems!

Edited by keithb7 (see edit history)
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57 minutes ago, 1937hd45 said:

Every electrical discussion is good for one never before mentioned tid bit, Why is there more voltage on the positive side? If you remove a perfectly good battery from your car in the fall and it is dead in the spring, were did the electricity go? Bob 

If the battery is dead, the chemical reaction inside the battery is no longer active.  In the old lead acid types the usual culprit was oxidation on the lead plates and accumulated junk in the base of the battery that created an internal short between the lead plates.

 

As said above, the positive and negative charge in the battery that are normally separated all combine and then there is no free electrons to travel down the wire, no current flows. Think of no more water in the pipe.  By charging the battery the positive and negative charges are again separated and are able to again recombine by traveling inside the wire to make current flow.  Battery charging is the process of keeping the chemical reaction alive.  The act of separating the positive and negative charge in a lithium ion battery has to be well regulated else excessive heat develops and the battery literally burns up.  

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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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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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