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Battery disconnect switch


Buick35

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So now I'm confused.  Literally ever cutout I have ever seen - not a hundred but close - were on the power cable not the ground.   I'm using positive/negative here because prewar is not standardized on negative ground.

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Switching at either terminal breaks the circuit.  For example, typically when working on a negative ground car, practice is to disconnect the negative (ground) cable.  That eliminates the possibility of shorting the starter cable to ground with a wrench.

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On 2/10/2024 at 1:00 PM, Bloo said:

I don't think you want any sort of switch on a high compression 472. Those cars draw what seems like too much current even when nothing is wrong. I had one, and battery cables made of large welding cable are what finally made it crank with authority, even in cold weather.

In my business I have dozens of battery disconnects.  Some of these are large displacement high compression diesels that have to start these tractors in cold weather, granted here in California we rarely see temps drop below 25 degrees, however I included a picture of our old cat D8 H it has a displacement of 1,246 ci.

along with a picture of the Cat disconnect with removable key, I believe Cole Hersee makes these for Cat. Very pricey but they are reliable, I have never had one fail, the one on this unit is on the exterior of the tractor that has been outside since it was built in 1972.  I do not use this model on my cars for the simple reason that the key requires all my strength in my now older fingers to rotate it, when you are able to walk up to it at ground level it’s not bad, when it’s under a running board or under a seat , not so much! I also included pictures of non Cat equipment that we have modified using their switch, you are looking at triple 000 cable, even though it looks like we installed the switch on the positive cable as it is on the starter it is not, most tractors bring the negative ground cable back to the starter and that’s where we tapped in.  
  A interesting point on cable lugs, major tractor company’s crimp the ends of copper lugs on the cables without solder.  I ask about this as I always used a little solder , the tech told me they got away from solder for two reasons, one is under high amp draw the electrons face some resistance going through the solder compared to copper on copper , the second reason is if they are not properly crimped and you fill void with solder under high amp draw the solder could melt and you could end up burning up components as they arc and pull apart, not trying to start a controversy, just repeating what a factory representative told meIMG_0246.jpeg.54f998834ba37a7f52950b536285bb49.jpegIMG_0245.jpeg.6bc89b503b58d540fa7bf30a165ec0e7.jpegIMG_0227.jpeg.876b59a4f13bb31113bf0699ac2faebd.jpegIMG_1154.jpeg.bb1bf4721c5bb60d8d18d9f1dc0149e1.jpeg

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When you hear the word "circuit" think "circle".

 

There is nothing magic about a ground. The word "return" is occasionally used in electronics, and it makes a little more sense. The electrical current has to get back to whatever provided it, in this case the battery. If the current came from the battery, the only "ground" that does any good is the one on the battery itself. Think of the body or frame as a piece of wire leading back to the battery "ground" post. If you disconnect one post, the battery cannot do anything. It doesn't matter so much which one.

 

 "Always disconnect the negative first" is from more recent times and assumes a negative ground car. There is a reason. As you are disconnecting the battery you are surrounded by metal parts that are "grounded" to the battery. If you are on the positive post with your wrench, and you slip, you'll get sparks, maybe fire, explosion, etc. If you are on the negative post with the wrench (still talking about a negative ground car), nothing will happen. Then when you disconnect the positive, the battery cannot do anything, because it already has it's other post disconnected. You would have to get your wrench between the posts to cause a spark.

 

 

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2 hours ago, Bloo said:

When you hear the word "circuit" think "circle".

 

There is nothing magic about a ground. The word "return" is occasionally used in electronics, and it makes a little more sense. The electrical current has to get back to whatever provided it, in this case the battery. If the current came from the battery, the only "ground" that does any good is the one on the battery itself. Think of the body or frame as a piece of wire leading back to the battery "ground" post. If you disconnect one post, the battery cannot do anything. It doesn't matter so much which one.

 

 "Always disconnect the negative first" is from more recent times and assumes a negative ground car. There is a reason. As you are disconnecting the battery you are surrounded by metal parts that are "grounded" to the battery. If you are on the positive post with your wrench, and you slip, you'll get sparks, maybe fire, explosion, etc. If you are on the negative post with the wrench (still talking about a negative ground car), nothing will happen. Then when you disconnect the positive, the battery cannot do anything, because it already has it's other post disconnected. You would have to get your wrench between the posts to cause a spark.

 

 

Exactly as I was taught.    

 

Watched a new guy melt a box wrench doing just this on the positive battery post nut when it swung and contacted the grounded frame.  That wrench was as orange as a carrot.

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On 2/13/2024 at 5:12 AM, edinmass said:

Placement is important.........I have seen several cars dead on the side of the road when a foot or pocketbook killed the power going down the road and things start to cook.........so put them in spots where they won't accidentally get bumped into the off position. 

Update on placement of switch, after reading Ed’s  comments we realized that my other cars that have the vertical seat riser are safe from someone unintentionally shutting power.  However coming out of the floor in a spot that allows the seat to adjust, the ability to reach it and have it so feet do not touch was somewhat possible until we tried to line the location up with the obstacles under the floor boards , like the massive Packard frame and its gusset’s, the battery box, clutch vacuum booster, brake vacuum booster and master cylinder and then throw in the transmission, mounts and side mount shift mechanism.  So we went to plan B, it is now mounted under and behind the drivers side running board, it lines up with the B pillar where the front and rear doors meet for quick reference, when you walk up to the car.  Even though it is mounted high up, maybe 9”, a heavy metal guard was fabricated to protect the switch from debris and the possibility of something shutting it off while driving. You can’t see it and it’s fairly easy to find, thanks Ed.

IMG_0002.jpeg

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On 2/17/2024 at 1:09 PM, Bloo said:

When you hear the word "circuit" think "circle".

There is nothing magic about a ground. The word "return" is occasionally used in electronics, and it makes a little more sense. The electrical current has to get back to whatever provided it, in this case the battery. If the current came from the battery, the only "ground" that does any good is the one on the battery itself. Think of the body or frame as a piece of wire leading back to the battery "ground" post. If you disconnect one post, the battery cannot do anything. It doesn't matter so much which one.

 "Always disconnect the negative first" is from more recent times and assumes a negative ground car. There is a reason. As you are disconnecting the battery you are surrounded by metal parts that are "grounded" to the battery. If you are on the positive post with your wrench, and you slip, you'll get sparks, maybe fire, explosion, etc. If you are on the negative post with the wrench (still talking about a negative ground car), nothing will happen. Then when you disconnect the positive, the battery cannot do anything, because it already has it's other post disconnected. You would have to get your wrench between the posts to cause a spark.

Good post thanks. Perhaps it is confusing when we call the DC battery negative side as the "ground." The ground wires or the earth wires in your home literally lead to the ground. On a car there is no ground connection, only the circuit circle as Bloo calls it. 

Edited by 28Buick (see edit history)
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14 minutes ago, 28Buick said:

Good post thanks. Perhaps it is confusing when we call the DC battery negative side as the "ground." The ground wires or the earth wires in your home literally lead to the ground. On a car there is no ground connection, only the circuit circle s Bloo calls it. 

Moreover, there are *many* 6V cars using *positive* ground, my Pierces among them--and Fords, MoPaRs, and pre-1946 Cads.  I strongly prefer that we speak of 'ground side' vs 'hot side' so I don't have to go through the text and correct for my cars--except my Jeepster is indeed 6V negative ground.

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  • 2 weeks later...
On 2/18/2024 at 11:51 AM, ramair said:

Update on placement of switch, after reading Ed’s  comments we realized that my other cars that have the vertical seat riser are safe from someone unintentionally shutting power.  However coming out of the floor in a spot that allows the seat to adjust, the ability to reach it and have it so feet do not touch was somewhat possible until we tried to line the location up with the obstacles under the floor boards , like the massive Packard frame and its gusset’s, the battery box, clutch vacuum booster, brake vacuum booster and master cylinder and then throw in the transmission, mounts and side mount shift mechanism.  So we went to plan B, it is now mounted under and behind the drivers side running board, it lines up with the B pillar where the front and rear doors meet for quick reference, when you walk up to the car.  Even though it is mounted high up, maybe 9”, a heavy metal guard was fabricated to protect the switch from debris and the possibility of something shutting it off while driving. You can’t see it and it’s fairly easy to find, thanks Ed.

IMG_0002.jpeg

Good idea on the metal guard. Mine is mounted in about the same place as yours only on the passenger side without a guard.I also need to make one for my son's electric fuel pump on his v.w.

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7 hours ago, Buick35 said:

Good idea on the metal guard. Mine is mounted in about the same place as yours only on the passenger side without a guard.I also need to make one for my son's electric fuel pump on his v.w.

I have been thinking about a future modification, everyone I tell it to just shake their heads.  I am referring to it as the belt and suspenders system.  This is what I came up with after reading about the pluses and minus of having two batteries in parallel, I also took note of Ed’s system of having two batteries and only keeping one hooked up and then trading cables when needed. Since my car has a big enough tray to hold 2 Optima batteries, I propose that we hook the two batteries together on the negative posts to the starter solenoid, it is a positive ground system , then each positive post would have a cable coming out underneath the running board to two separate cutoff switch’s. The advantage would be each time I drive the car I could use the batteries alternatively, then if I had a hard start issue I could turn them both on .  I toyed with the idea of buying a Cole Hersee switch used on emergency vehicles that gives you 4 positions,

off - bat 1 -bat 2 - bat 1 & 2.  The issue for me is the shape of the knob is not conducive for your hand to know which position it is in , or my memory without being able to see it.  The idea of me crawling under the car each time didn’t excite me, that’s why the 2 switch next to each other makes more sense to me

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There are relatively inexpensive 4 position marine switches available that do just that . Positions are well marked and easy to read too . Problem might be the esthetics of being  bright yellow and red.

Not sure what their current capacity is as far as 6V systems go.

Just realized that I used 'inexpensive' and 'marine' in the same sentence which means I'm probably wrong about something.

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21 hours ago, bradsan said:

There are relatively inexpensive 4 position marine switches available that do just that . Positions are well marked and easy to read too . Problem might be the esthetics of being  bright yellow and red.

Not sure what their current capacity is as far as 6V systems go.

Just realized that I used 'inexpensive' and 'marine' in the same sentence which means I'm probably wrong about something.

I looked at those switches on the internet, only the Cole Hersee had a knob with a pointer that one can “ feel the position, but what was unusual was the fact it is kind of light on amp rating compared to a few other brands.  Cole Hersee stuff is usually the heavy high quality type.  

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On 2/29/2024 at 12:44 AM, ramair said:

I have been thinking about a future modification, everyone I tell it to just shake their heads.  I am referring to it as the belt and suspenders system.  This is what I came up with after reading about the pluses and minus of having two batteries in parallel, I also took note of Ed’s system of having two batteries and only keeping one hooked up and then trading cables when needed. Since my car has a big enough tray to hold 2 Optima batteries, I propose that we hook the two batteries together on the negative posts to the starter solenoid, it is a positive ground system , then each positive post would have a cable coming out underneath the running board to two separate cutoff switch’s. The advantage would be each time I drive the car I could use the batteries alternatively, then if I had a hard start issue I could turn them both on .  I toyed with the idea of buying a Cole Hersee switch used on emergency vehicles that gives you 4 positions,

off - bat 1 -bat 2 - bat 1 & 2.  The issue for me is the shape of the knob is not conducive for your hand to know which position it is in , or my memory without being able to see it.  The idea of me crawling under the car each time didn’t excite me, that’s why the 2 switch next to each other makes more sense to me

 

Sounds like a complex solution in search of a problem.

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8 hours ago, Matt Harwood said:

 

Sounds like a complex solution in search of a problem

Matt, that is why others shake their heads. I put more miles touring by myself, so without another 6 volt car to jump off of, the 5,500 pound weight of the car for push starting, then throw in the difficulty of accessing the the starter on the later twelves makes it tough to jump off of a 12 volt modern car without risk. So I view it as wait for AAA to load you and haul you home or “click” and done. With that said I will probably run it the way it is for the upcoming year, but the first time I have an issue, I have a plan.  I threw this idea out here to see if anyone could see a detriment other than making Optima richer ?

Edited by ramair
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Why not put a spare battery in a box and put it in the  trunk with jumper cables.  In my mind the risk of failure is minimal.  The equipment can be moved to other cars if needed.

 

Bob Engle

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On 2/16/2024 at 4:47 PM, alsancle said:

I have only seen cut off switches installed on the power cable, not the ground cable.   That makes sense to me as a wire shorting to ground in the harness could cause a fire if the cutout is installed on the ground cable.

NO!!!!!  If there is no connection from the negative battery terminal to the chassis, negative ground car, how in the world is a short in the wiring harness going to pass current? Draw the diagram.

 

 

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  • 3 weeks later...

This is a related 6V question, with apologies for switching from cutoff switch, about prewar DELCO batteries. I searched this forum and have not found any wisdom on a correct battery. The BCA judging handbook says:

A one point deduction should be made for incorrect battery manufacturer. Batteries for older models may be of modern manufacture.
Batteries in all models after 1924 are of DELCO manufacture.

My picture shows I have a Duracell. If the car is judged will it be grounded by a floorboard lift that reveals a rogue battery? It seems current Delco 6V batteries are mostly wired for golf carts. A distilled Chevy post says "In 1929 Chevrolet did not use a Delco battery, they had not been "invented" at that time."  This open observation contradicts the BCA charge. Some say Exide closes the circuit. Is there current advice on Delco authenticity? Thanks.

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On 3/20/2024 at 11:52 AM, 28Buick said:

This is a related 6V question, with apologies for switching from cutoff switch, about prewar DELCO batteries. I searched this forum and have not found any wisdom on a correct battery. The BCA judging handbook says:

A one point deduction should be made for incorrect battery manufacturer. Batteries for older models may be of modern manufacture.
Batteries in all models after 1924 are of DELCO manufacture.

My picture shows I have a Duracell. If the car is judged will it be grounded by a floorboard lift that reveals a rogue battery? It seems current Delco 6V batteries are mostly wired for golf carts. A distilled Chevy post says "In 1929 Chevrolet did not use a Delco battery, they had not been "invented" at that time."  This open observation contradicts the BCA charge. Some say Exide closes the circuit. Is there current advice on Delco authenticity? Thanks.

If I recall the discussion of this at the judges meeting at the last national meet, batteries under floors/seats that are not visible can't be judged and no points are deducted. 

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On 3/21/2024 at 4:36 PM, Edwin The Kid said:

If I recall the discussion of this at the judges meeting at the last national meet, batteries under floors/seats that are not visible can't be judged and no points are deducted. 

Thank you Edwin for this insight. Seems a bit picky to judge the brand of electrons.

I have a cutoff switch and do not wear a watch since my Rolex gave up. I just say "Alexa, what time is it?"

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