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installing a batt. disconnect switch

G3isMe

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Thanks Papakb. I guess it is time to install a cutoff!


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I ordered a switch, wire, and some battery cable fittings. I now need to figure out where to install and mount the switch. I have the large Napa batterys and they don't leave much room in the battery box for a switch mount. Any suggestions.
 

Coug

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I ordered a switch, wire, and some battery cable fittings. I now need to figure out where to install and mount the switch. I have the large Napa batterys and they don't leave much room in the battery box for a switch mount. Any suggestions.
If you are set up as a 4 door, you can do it out the back of the battery box. If keeping as a 2 door, there is a little space directly above the NATO slave plug, or if you want it over by the driver's side depending on what you have installed right now you can do it in place of the deep water fording kit's vent valve, or like mine I installed just in front of the transmission COM port ahead of the shifter and by the doghouse.

c4c37ffda0517369f753f60e912be815f1fa3e26-2.jpg
c4c37ffda0517369f753f60e912be815f1fa3e26-1.jpg
 

Inspector 1

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Yes, that is what I am trying to say (sometimes words aren't really very good for explaining a concept, but I think we are both saying the same thing here)


View attachment 790629
Here is a little closer picture of the Shunt. The actual nomenclature in the manual might be different, I haven't looked it up.
It's a device that measures the amount of voltage drop over a gap with known resistance (in this case all those flat bars), then the gauge is what uses that voltage drop to tell you how many amps are being either charged or discharged through that shunt.
I wanted to thank you for the pics and information. I finally had time to install switch. Works like a champ. Thanks again.
 

Retiredwarhorses

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just my professional opinion....

-Always install the BCO to break the negative
-Use the proper sized wire, not the undersized crap provided in all the kits
-keep the BCO as close to the battery compartment as possible
-use a rated HD marine application BCO
-not a good idea to have the BCO mounted facing up in areas of water, such as next too your ste/ice.
 
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Most battery shops can make a cable on the spot. They usually have the loop ends and wire in stock. And they have the swedge tool for a sure connection. I used a 16” oo cable with 3/8” ends. Cost like $9 and took about 15 minutes to make it and pay for it.
 

Andyrv6av8r

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just my professional opinion....

-Always install the BCO to break the negative
-Use the proper sized wire, not the undersized crap provided in all the kits
-keep the BCO as close to the battery compartment as possible
-use a rated HD marine application BCO
-not a good idea to have the BCO mounted facing up in areas of water, such as next too your ste/ice.
What would it hurt to break the 24 volt positive wire with a heavy duty relay?
 

Retiredwarhorses

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What would it hurt to break the 24 volt positive wire with a heavy duty relay?
There's considerable controversy over whether it's best to hook up the master-shutoff ("kill") switch to the battery's positive or negative side. NHRA rules still mandate a positive-side hookup, but most stock-car sanctioning bodies want the kill switch on the negative side. I vote for the negative side if it's legal. On a switch connected through the positive side, the exposed terminals on the back of the switch or a broken positive cable could contact the sheetmetal or frame during a crash, creating a short to ground and safety hazard. The negative cable connects to the body ground already—so there's no additional danger if it rubs. It's the same principle as why you should always disconnect the battery's negative side first before performing electrical service.
 

Andyrv6av8r

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There's considerable controversy over whether it's best to hook up the master-shutoff ("kill") switch to the battery's positive or negative side. NHRA rules still mandate a positive-side hookup, but most stock-car sanctioning bodies want the kill switch on the negative side. I vote for the negative side if it's legal. On a switch connected through the positive side, the exposed terminals on the back of the switch or a broken positive cable could contact the sheetmetal or frame during a crash, creating a short to ground and safety hazard. The negative cable connects to the body ground already—so there's no additional danger if it rubs. It's the same principle as why you should always disconnect the battery's negative side first before performing electrical service.
I have mine wired that way with a keyed switch turning the relay on and off , thus disconnecting the batteries. That way I leave my light switch in the ON position and I never worry about turning them on and off. It's worked fine for several months so far.
 

papakb

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Most contactors (relays) that will handle the power needed for a HMMWV have heavy duty coils that draw lots of power that's wasted and could be used elsewhere. While contactors and relays do similar jobs the term contactor is used for systems switching more than 6 amps.
 

Retiredwarhorses

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Most battery shops can make a cable on the spot. They usually have the loop ends and wire in stock. And they have the swedge tool for a sure connection. I used a 16” oo cable with 3/8” ends. Cost like $9 and took about 15 minutes to make it and pay for it.
never seen a battery shop in my 30yrs in the business...at least not here in the Bay Area, but never actually looked for one either.
 
92
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Perrysburg OH
I used an CNHI brand switch for a 24v Case dozer. The switch is all weather and very heavy duty. The list price was $103.00 but my son is the parts manager and I got it for $65.00. I know in the heavy equipment world they are always on the negative side. Modern heavy equipment has way more electronics than a HMMWV. it really is a very heavy duty switch.
 

AtlantaSBR

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So I installed my battery disconnect switch today and even with it shut off the wait light still flashes for a split second. I installed it in between the rear battery negative terminal and the shunt. Is this normal?

My switch appears to be the same Pollak switch that RWH shows in the picture above
 

Coug

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So I installed my battery disconnect switch today and even with it shut off the wait light still flashes for a split second. I installed it in between the rear battery negative terminal and the shunt. Is this normal?

My switch appears to be the same Pollak switch that RWH shows in the picture above
It does that for me as well.
I can only assume there is some stored power in a capacitor or something that doesn't drain away very quickly until a load is applied.
 

Andyrv6av8r

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It does that for me as well.
I can only assume there is some stored power in a capacitor or something that doesn't drain away very quickly until a load is applied.
I have mine on the positive cable, 24 volt side. Zero problems in over a year. I've done it in every military truck I have owned for 10 years.
 
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