Military Cutoff Disconnect Switch HMMWV Battery

[nikojo]

I have a military cutoff switch kit and it's instructions.

It essentially cuts off the positive feed to the busbar from the front battery and the feed to (from) the voltage regulator and 12V circuit (TCM/circuit breaker) using a 4 pole/2 switch box.

My concern is cutting off the positive feed only can still short the battery when working on the battery, ie wrench contact from positive battery lug to battery box.

My thought was to use the part of the cutoff to disconnect the main negative feed to the shunt/main ground. And use the other part similar to the military spec, ie cutoff the voltage regulator and the 12V feed.

This would disconnect all ground so I couldn't short any of the positive lugs to the body/box. It would also prevent 'false ground' coming back through the voltage regulator/12V circuit.

Am I understanding this correctly??

I would install a separate fuse box for the 12v circuits but I did not include for simplicity.

I am trying to avoid a 24v to 12v converter as I have a 200amp generator that will balance the battery and don't plan many 12v circuits other than AC/heater blowers and TCM and maybe minimal radio.

I've included a last option that cutsoff the ground feed and also the feed between the two batteries. If I did this I would include a relay to cutoff 12V circuits so it can't drain the battery.......could even wire a 24V relay fed off the busbar with a ground connected to the cutoff so it does this automatically.

 

[Mogman]

I see no reason that will not work, that is the same thing I am doing with two switches on the Detroit.

 

[nikojo]

I see no reason that will not work, that is the same thing I am doing with two switches on the Detroit.

Why would the military not do it this way, ie use the ground as the cutoff rather than the positive feed?

Have to think they put more thought into this than I did LOL.

 

[Mogman]

Probably for the same reason I have seen instructions on 12V systems for decades that say to remove the positive battery cable to de-energize the vehicle, makes no difference on a 12V system and it is safer to remove the negative, just like it is safer to cable up to the switch on the negative side as you suggest.
Many folks tend to ignore the "ground" side of systems which can be a mistake when troubleshooting a problem.

 

[royg]

Interesting.

Can you share details on the switch you've found?

I've been using the flaming river switch with removable key on the positive side but it's only single pole(which does prevent truck from being started, but doesn't actually kill the 12V side. lousy I know.)

I've probably been looking in the wrong places but all the two pole disconnect switches I've seen are rated less for the second pole.

Like the "Longacre Battery Disconnect Switches 52-45782" on summit racing is rated 175 amps on the main pole and 125 amps on the "alternator cutoff" pole

Longacre Racing Products 52-45782 Longacre Battery Disconnect Switches | Summit Racing

Free Shipping - Longacre Battery Disconnect Switches with qualifying orders of $109. Shop Battery Disconnect Switches at Summit Racing.

www.summitracing.com

 

[Mogman]

Interesting.

Can you share details on the switch you've found?

I've been using the flaming river switch with removable key on the positive side but it's only single pole(which does prevent truck from being started, but doesn't actually kill the 12V side. lousy I know.)

I've probably been looking in the wrong places but all the two pole disconnect switches I've seen are rated less for the second pole.

Like the "Longacre Battery Disconnect Switches 52-45782" on summit racing is rated 175 amps on the main pole and 125 amps on the "alternator cutoff" pole

Longacre Racing Products 52-45782 Longacre Battery Disconnect Switches | Summit Racing

Free Shipping - Longacre Battery Disconnect Switches with qualifying orders of $109. Shop Battery Disconnect Switches at Summit Racing.

www.summitracing.com

You do not need a fully rated second switch as the 12V side does not have the current flow the main (24V) side does.
BTW IMHO that switch is fairly marginal on the main side for a HMMWV.

 

[Mogman]

Interesting.

Can you share details on the switch you've found?

I've been using the flaming river switch with removable key on the positive side but it's only single pole(which does prevent truck from being started, but doesn't actually kill the 12V side. lousy I know.)

I've probably been looking in the wrong places but all the two pole disconnect switches I've seen are rated less for the second pole.

Like the "Longacre Battery Disconnect Switches 52-45782" on summit racing is rated 175 amps on the main pole and 125 amps on the "alternator cutoff" pole

Longacre Racing Products 52-45782 Longacre Battery Disconnect Switches | Summit Racing

Free Shipping - Longacre Battery Disconnect Switches with qualifying orders of $109. Shop Battery Disconnect Switches at Summit Racing.

www.summitracing.com

You can use two switches which is what I do, I use a Cole Hersey for the 12V which is heavy enough for the 12V, that Flaming River switch looks like a good one, it has close the same ratings as the Hella switches I use, 2500A for 5sec. VS 2500A for 10sec for the Hella
I just remember to disconnect the 12V first and connect the 12V last

 

[Mainsail]

My concern is cutting off the positive feed only can still short the battery when working on the battery, ie wrench contact from positive battery lug to battery box.

If you want to be safe for this aspect, go to harbor freight and buy a few cheap wrenches and plastidip or insulate them some other way, then keep those wrenches in the battery box. Nothing in there is so tight that you'd ever break a cheap wrench.

 

[nikojo]

Interesting.

Can you share details on the switch you've found?

Here are some pics of the two switches I have now. The one with the black handle is the one that comes in military kit. The one with the red handle I got from a friend. They are both 2 pole and 500amp per pole. They are made by same swiss company (Kissling). High quality. www.kisslingworld.com

You can find online pretty easy about $180-220.

 

[frauhansen]

I have a military cutoff switch kit and it's instructions.

It essentially cuts off the positive feed to the busbar from the front battery and the feed to (from) the voltage regulator and 12V circuit (TCM/circuit breaker) using a 4 pole/2 switch box.

My concern is cutting off the positive feed only can still short the battery when working on the battery, ie wrench contact from positive battery lug to battery box.

My thought was to use the part of the cutoff to disconnect the main negative feed to the shunt/main ground. And use the other part similar to the military spec, ie cutoff the voltage regulator and the 12V feed.

This would disconnect all ground so I couldn't short any of the positive lugs to the body/box. It would also prevent 'false ground' coming back through the voltage regulator/12V circuit.

Am I understanding this correctly??

I would install a separate fuse box for the 12v circuits but I did not include for simplicity.

I am trying to avoid a 24v to 12v converter as I have a 200amp generator that will balance the battery and don't plan many 12v circuits other than AC/heater blowers and TCM and maybe minimal radio.

I've included a last option that cutsoff the ground feed and also the feed between the two batteries. If I did this I would include a relay to cutoff 12V circuits so it can't drain the battery.......could even wire a 24V relay fed off the busbar with a ground connected to the cutoff so it does this automatically.

In one of your version... you sucking the juce only from one battery... so you will run into a unbalanced battery situation....

 

[nikojo]

In one of your version... you sucking the juce only from one battery... so you will run into a unbalanced battery situation....

That’s the way they are set up from factory at least for the TCM 12V.

I have a 200amp alternator with 14V feed. My understanding is this will keep it in balance.

Is this wrong?

 

[Crapgame]

The old Ranger Land Rover Defender RSOV Ranger Special Operations Vehicle used a Cole-Hersee M-750 rotary battery disconnect switch that allows you to cut power from either 12v, 24v or both:
Cole Hersee Standard Battery Switch [M-750-BP] (delawarepaddlesports.com)

Cole Hersee also makes a key-lockable switch, M-751, this link shows the suggested wire diagram:
Dual Battery Key Switch Select Discon – Cole Hersee

 

[Mogman]

The old Ranger Land Rover Defender RSOV Ranger Special Operations Vehicle used a Cole-Hersee M-750 rotary battery disconnect switch that allows you to cut power from either 12v, 24v or both:
Cole Hersee Standard Battery Switch [M-750-BP] (delawarepaddlesports.com)
View attachment 887593
Cole Hersee also makes a key-lockable switch, M-751, this link shows the suggested wire diagram:
Dual Battery Key Switch Select Discon – Cole Hersee
View attachment 887594

That switch is made for a dual battery system like a boat with dual batteries, not meant to switch a 24V system and the 12V component.
That requires two separate switches, completely isolated from each other weather or not it is controlled by one mechanism, It would require 4 poles not three. Besides being a little light at 500A int. (many of these are rated for only 2-3 seconds)

 

[Crapgame]

BTW: TruckGuy and I are working on getting the label/instruction plates for the military 57K6230 Battery Cutoff Switch Kit replicated if anybody else is trying to make their own kit from the Kissling 35.553 Switch and self scrounged parts instead of paying $400-850 for the packaged AMG kit. Would have the dashboard Vehicle is Equiped With Battery Disconnect Switch, and the On/Off plate & Connecting Auxilliary Equipment plates for the battery box side.


The yellow Battery Connections plate for battery box in the kit is nearly identical to Part 12339107 available, for now, online for about $9 each: Instruction Plate 12339107 Aluminum Alloy 1 1/4-Ton Hmmwv Truck Data Plate - Mibot LLC (mibotparts.com)

There is a vinyl decal alternate version 12339107 available, too, example from Rico in LA 2/$9.45:
-LOT of 2- HMMWV Connecting battery cables decal DATA PLATE M998 M1025 12339107 | eBay

 

[nikojo]

-LOT of 2- HMMWV Connecting battery cables decal DATA PLATE M998 M1025 12339107 | eBay

Great idea and great link. Did not know about that site. Thanks.

 

[nikojo]

I hooked it all up tonight. Main ground is on switch. Did not add the interbattery cable to the switch or the 12V or 14V alternator to the switch.

Interestingly the lights can still go on and some of the gauges click on. I did NOT try to cycle plugs or try to start for fear of blowing something.

Clearly even disconnecting the main ground is not enough. My thought is the connection between the batteries must be cut off to truly eliminate some the circuits still looking for ground though the voltage regulator/alternator connection on the rear battery.

 

[Mogman]

I hooked it all up tonight. Main ground is on switch. Did not add the interbattery cable to the switch or the 12V or 14V alternator to the switch.

Interestingly the lights can still go on and some of the gauges click on. I did NOT try to cycle plugs or try to start for fear of blowing something.

Clearly even disconnecting the main ground is not enough. My thought is the connection between the batteries must be cut off to truly eliminate some the circuits still looking for ground though the voltage regulator/alternator connection on the rear battery.

If you disconnect the ground and the lead to the connection between the batteries (12V) nothing will have power, you do not have to disconnect the connection between the batteries.

 

[NDT]

Can someone please post a schematic of how the military kit is hooked up?

 

[nikojo]

Can someone please post a schematic of how the military kit is hooked up?

NDT it’s the second pic I posted. That’s military setup. Cut off at feed.


Sent from my iPhone using Tapatalk

 

[nikojo]

If you disconnect the ground and the lead to the connection between the batteries (12V) nothing will have power, you do not have to disconnect the connection between the batteries.

Mogman I think that’s the point lol……I want to cut everything off when I use the switch.


Sent from my iPhone using Tapatalk