Battery disconnect switch

[Industrial Toys]

I just love people chiming in on electrical matters. Should start with Moma always said . . .

It's on my list of things to do, add disconnects. Especially on my Steiner, where the battery cables go through the articulation point along with the fuel lines.

Good to know that the OEMS are putting it on the GND. Usually that's just easier and safer for exposed terminals.

Note, cheap chinese disconnects (like from Princess Auto/HF) can give you grief.

 

[Peter 315]

On all are komatsu equiptment its on the ground side, also it is a keyed switch

 

[WranglerX]

Keep in mind people this whole thing started when OP objected to fact in some applications it is necessary to disconnect positive side of battery and alternator/generator output to shut down a running engine....

Not merely to disconnect battery from electrical system to prevent theft or battery drain or to remove short circuit hazard when wrenching around battery... To remove short circuit hazard ALWAYS remove negative (ground) cable first also avoiding crossing negative and positive terminals with wrench when disconnecting.....

Dale

 

[Industrial Toys]

Keyed? Or a Generic key or just a plastic paddle thing?

 

[SPYDERLK]

It ads only 2 connections on the switch.

Dont forget the make/break connection of the switch itself. So three sources of greater resistance than the cable. Or five if you count the crimp terminals. ... It will be very lossy in comparison, but we would be comparing near zero to only several times near zero if all connections were optimal. Then of course we have to ensure connections and switch performance are stably optimal. A little resistance/heat will cascade a failure mode aggravated by every cycle of high current.

 

[Industrial Toys]

Definitely. Use a junky switch and you will have created trouble for yourself. It also depends what you are switching. A liittle Jap diesel or a D9?

 

[CobyRupert]

Current flow is same in hot lead and ground.... Amperage flow (current) is a loop originating and terminating at battery... This is why ground and positive battery main leads are same gauge wire...

Your comment is not valid...

Dale

I think Lou is right about the instructions.
You are right about amperage flow loops.
Voltage is also a rating. 12VDC isn’t much to overcome with insulation, but it’s something. My ATV’s disconnect is just two bare metal bars with insulation between them and a common removable screw that threads and connects both as the “disconnect”.
This is not rated for the positive post, battery is under seat, you’d fry your...on every bump.

 

[LouNY]

Current flow is same in hot lead and ground.... Amperage flow (current) is a loop originating and terminating at battery... This is why ground and positive battery main leads are same gauge wire...

Your comment is not valid...

Dale

I believe that you are somewhat in error,
while current flow may remain the same the wattage does not nor does the voltage,
The wattage is what is doing the work.
Additionally many times the negative battery leads are not the same size as the positive,
on a negative ground system.

 

[WranglerX]

I believe that you are somewhat in error,
while current flow may remain the same the wattage does not nor does the voltage,
The wattage is what is doing the work.
Additionally many times the negative battery leads are not the same size as the positive,
on a negative ground system.

38 years in DC power system's some systems at 24 VDC and some at 48VDC, some just a few amps current some capable of 10,000 amps (or more) .... Conductors were always same gauge wire from maybe 20 gauge solid to multiple runs of 750,000 CM cable for positive and matching number of cable runs for negative, prefer to use theory current flow is same in all conductors, it make system easier to design, maintain and keep functional... And does not add confusion to discussion...

Each cell puts our about 2.17 volts and there is 24 cells in string and can produce thousands amps till chemical reaction is depleted in short circuit conditions.

On this racking there is two strings of batteries producing 50 volts per strings.... Probable good for 500 AH rating per string depending on battery specifications...

Dale

 

[LouNY]

About the same number of years in Industrial Controls, Electronic, Pneumatic, Steam, Hydraulic and Electrical in power plants, petro chemical, water, paper, pharmaceutical.
From low voltage DC to 13,500 AC.
From #28 to 500MCM as well as 1/8" to 1" tubing.
I prefer what works reliably at the lower cost.

 

[Peter 315]

Keyed? Or a Generic key or just a plastic paddle thing?

no a real metal key all the keys are the same even the ignition keys a different key but fits all the machines

 

[SPYDERLK]

Current flow is same in hot lead and ground.... Amperage flow (current) is a loop originating and terminating at battery... This is why ground and positive battery main leads are same gauge wire...

Your comment is not valid...

Dale

I believe that you are somewhat in error,
while current flow may remain the same the wattage does not nor does the voltage,
The wattage is what is doing the work.
Additionally many times the negative battery leads are not the same size as the positive,
on a negative ground system.

While all this can be true youve got a lot of explaining to do to make it clear what youre talking about. I would prefer not to guess.

 

[BertZegers]

Keep in mind people this whole thing started when OP objected to fact in some applications it is necessary to disconnect positive side of battery and alternator/generator output to shut down a running engine....

Not merely to disconnect battery from electrical system to prevent theft or battery drain or to remove short circuit hazard when wrenching around battery... To remove short circuit hazard ALWAYS remove negative (ground) cable first also avoiding crossing negative and positive terminals with wrench when disconnecting.....

Dale

Or disconnect the battery switch in the ground.:laughing:

My Kubota's need electricity for the stop solenoid to shut of the engine!
There is a mechanical shut off for if the electricity fails.

 

[WranglerX]

About the same number of years in Industrial Controls, Electronic, Pneumatic, Steam, Hydraulic and Electrical in power plants, petro chemical, water, paper, pharmaceutical.
From low voltage DC to 13,500 AC.
From #28 to 500MCM as well as 1/8" to 1" tubing.
I prefer what works reliably at the lower cost.

I can respect that...

But I don't think getting into the facts of power consumption is germain to how and best place for disconnect switch for average person...

Dale

 

[LouNY]

I can respect that...

But I don't think getting into the facts of power consumption is germain to how and best place for disconnect switch for average person...

Dale

Could be.

In that case I would still place it in the ground line as it provides the best protection from electrical shorts that could cause fires and equipment damage.
If needed or desired for computer or even radio memory retention a low amp fused line can be added.

 

[WranglerX]

Could be.

In that case I would still place it in the ground line as it provides the best protection from electrical shorts that could cause fires and equipment damage.
If needed or desired for computer or even radio memory retention a low amp fused line can be added.

Yeah like the yellow wire on [some] radios that remains hot so memory stay alive for stations one has selected...

Dale

 

[Cornerz]

One thing I haven’t read in the thread yet is the effect of cutting battery power if the tractor is running. Not an issue if you only want the switch to prevent parasitic drain, but if you want the switch to disconnect the battery and kill the tractor (gas tractor- Diesel may still run depending on it’s fuel delivery system etc) you can damage some more complicated tractor ignition systems.

There is a kill switch made that performs three actions in one selection - disconnect battery positive line, disconnect alternator output, and send alternator output to ground thru a resistor. These are used as safety devices on most race cars, with a few benefits. Primarily, they can prevent damage to electronics that may be sensitive to sudden power fluctuations. And they shut the engine off when activated.

Commonly referred to as an FIA Kill Switch. Here’s a description “four-post master kill switch is built to FIA specs, This switch has three sets of contacts for cars with alternators. The main contacts disconnect the battery while the auxiliary contacts disconnect the ignition coil and short the alternator output to ground through a 3 ohm resistor that is furnished with the switch. A removable actuating key with splash guard, weather-proof cap, resistor and installation instructions are included.”

 

[WranglerX]

One thing I haven’t read in the thread yet is the effect of cutting battery power if the tractor is running. Not an issue if you only want the switch to prevent parasitic drain, but if you want the switch to disconnect the battery and kill the tractor (gas tractor- Diesel may still run depending on it’s fuel delivery system etc) you can damage some more complicated tractor ignition systems.

There is a kill switch made that performs three actions in one selection - disconnect battery positive line, disconnect alternator output, and send alternator output to ground thru a resistor. These are used as safety devices on most race cars, with a few benefits. Primarily, they can prevent damage to electronics that may be sensitive to sudden power fluctuations. And they shut the engine off when activated.

Commonly referred to as an FIA Kill Switch. Here’s a description “four-post master kill switch is built to FIA specs, This switch has three sets of contacts for cars with alternators. The main contacts disconnect the battery while the auxiliary contacts disconnect the ignition coil and short the alternator output to ground through a 3 ohm resistor that is furnished with the switch. A removable actuating key with splash guard, weather-proof cap, resistor and installation instructions are included.”

This types of switch were mentioned in ammeter thread where this thread was a diversion from...

https://www.tractorbynet.com/forums/owning-operating/421257-ammeter-question-8.html#post5635718

Dale

 

[thunderworks]

Resurrecting an old post . . . I need to leave my tractor at my land, 10 miles from my home and am interested in a battery disconnect as additional theft deterrent. I am an electrical novice (that's being generous. I know next to nothing about electrical systems). Will the inexpensive plastic keyed disconnect, wired to the negative side of my battery do the trick? Several posts in the thread suggest that these disconnect switches can add problems, but they don't indicate what those problems are.

 

[JethroB]

If I ever have the need for theft protection I’ll try replacing the main fuse in the fuse box with a dummy or blown fuse. I figure most opportunistic thieves aren’t going to take the time to diagnose the problem or carry the proper fuse with them.