battery cutoff on negative wire

I have read a lot about battery cut off switches. I have a 12v 180amp cutoff switch and was wondering about just putting it on the negative “ground” side. Essentially just gutting off the ground to kill the batteries.

That is the correct way from what I have been told.

Thats the way all mine are set up.

I am guessing that it doesnt matter, as long as you break the circuit. But anyway it has worked well on my five ton. Now the batterries are always up when I hop in after a month or two of sitting. If you freeze a set of dead batteries in the winter, they are shot. Ask me how I know. Now , next is the m211, that I always have to remove the bat cable or they go dead in a few days! Dont ask me why these mil trucks drain down, I havent heard a good answer to that yet! You would think once the ignition was off it would stop all battery supplied things, but obviously it does not.

Put mine on the negative side
Its rated at 190amp continuous and 1000amp rush.
Doghead recently put up a good post which stated that for DC current, negative side is the prefered side for a cutoff

take care about the size of the switch..... a 12V 180A can handle 24V 90A

Bill W nice to see someone is making a hold down for different battries. Good job nice and simple.

The Feds require that a battery disconnect switch in a schoolbus must be installed in the negative (grounded) cable. The reason is that if the battery switch ever fails or shorts, it won't start a fire - plus if anything ever contacts the switch's terminals, it won't result in a short circuit. That's one advantage to a GMC - the batteries are installed under the hood, on the front of the firewall. A battery disconnect can go through the firewall, and the switch handle can be tucked up under the dash so it's out of sight

I would have never guessed that. Good to know. I'm installing new Yellowtop Optima batteries in my golf cart today, with a cutoff switch, and I would have put it on the positive side, leaving the ground in place. My traditional way of thinking is a good ground is safety while working. Thanks.

Since we're on the topic of cut-off switches. I wanted to put one on the link between the two batteries, one main reason is so that I could charge the each battery with a 12v charger/desulfurizer. The second would be to disable the Deuce. Would putting the disconnect between the two batteries cause any unwanted issues? Thanks for your input.

I was thinking of one like this or something similar..

There is no reason to disconnect the "dogbone" cable while charging the batteries with 2 separate chargers at the same time.

doghead said:

There is no reason to disconnect the "dogbone" cable while charging the batteries with 2 separate chargers at the same time.

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You are correct doghead if the chargers have a floating output. If they do not it might get interesting as then you would have one point on each battery at the same potential. Most newer chargers have floating outputs. There are still a lot of older chargers around that do not use floating outputs.

If you are not sure which type of charger you have I would disconnect the dogbone just to be safe.

59apache said:

take care about the size of the switch..... a 12V 180A can handle 24V 90A

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I don't think that is correct. The switch is not dissipating the full power of the circuit, and in this application it's generally not going to be opened under load. As long as it's rated for use in a 24V system, the current rating should be the same for that service.

DeucesWild11 said:

I was thinking of one like this or something similar..

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I've used those before. They're really flimsy, and I don't think I'd trust one under the heavy cranking load of a big diesel engine. I have one in my MEP-003A, but I think I'll replace it with something else next time I work on the set.

I've had good results with the Pollak brand of battery disconnect switches, which are the same style as the one that Bill W pictured. They're available either with a knob or a removable key. Note that the keys are all the same and it's a simple warded lock, so the security provided is limited. They turn up on eBay.

As much as I prefer to avoid low-quality imported stuff, I picked up an inexpensive "Heavy Duty Battery Cutoff Switch" (part number 66789) from Harbor Freight to play with, and it appears to be better-made than I've usually come to expect from HF's electrical products. I haven't tried using one in one of my MVs, but it looks to me like it might be an acceptable option for somebody on a tight budget. I don't think they're carrying that cheapo knockoff of the Hella keyed switches any more. I would never trust their fuses, based on accounts I've read of them.

That battery-box-mounted switch installation looks nice and neat. Good job!

Thanks guys, I have two brand new BatteryMINDer Charger/Maintainer/Desulfator — 1.3 Amp, 12 Volt, Model# 12117. They don't say anything about a floating charge (but probably have them) and they have the pulse for the Desulfurizing. Not sure if that makes a difference. I was thinking of the disconnect as well as another way to disable the Deuce.. Just wanted to make sure I wasn't doing any damage by having the disconnect on the dogbone. Probably not but just wanted to ask to be sure.. Thanks!

nf6x said:

I don't think that is correct. The switch is not dissipating the full power of the circuit, and in this application it's generally not going to be opened under load. As long as it's rated for use in a 24V system, the current rating should be the same for that service.

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i can't prove right now - what i know is that many switches has different amperage at 12V or 24V. So i assume that the load in W is crucial.

so if Parlusk writes he has a switch that is rated 180A @ 12V
i dont believe it is rated 180A @ 24V .

100 Amp Battery Master Switch - Accessories, Battery Switches - Hella Marine

go to specs....

59, that is a fine switch with a 2500A 10 second rating! I use the one just below it with the removable red handle on my trailer, it doesn't have the high current draw potential. I'm going to use the one you had a link to for my HEMTT, thanks!

stalwart, if you look for a switch that offers more permanent capacity
trial the Bosch 0 341 002 003
24V 250A 2500A (5 sec.)
also availible in 2pole switching off...
Flaming River has also very nice switches.

Thanks, I think you'll find from the dimensions they are EXACTLY the same switch from BOTH Hella and Bosch. I especially like the 2 pole for 12 and 24V disconnect when upsing a battery equalizer. Thanks again!

I'll look for some of those Bosch switches to try. The double pole one looks promising for CUCV applications. Thanks!