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To fully protect it requires a dual (DPST) or two battery switches, one on the ground cable and one disconnecting the 12V tap. Originally two wires, one to the alt and one to the trans.
Just be careful on what you settle on, you cannot beat physics, one of the most important things about a high current switch is the pressure applied to the contacts, just as important as the surface area of the contacts, when you crank down on that Hella switch you get the idea.Wow- that Hella switch is a helluva switch!
I'll look for a DPST to keep it simple, probably one with a key.
I used a 200 amp rated battery disconnect that is used in caterpillar earth moving equipment.
3 speed trucks with the 60 amp alternator don't.
Any vehicle that is using a 12V tap between the batteries, this would be all 4 speed HMMWV's but some folks are using the tap on 3 speed HMMWV's for other reasons, I have seen fire departments fry expensive radios on 2 1/2 ton trucks using a negative switch only, they forget to switch the batteries on jump in and try to start the truck, then wonder why their radio won't work. Irregardless of the fact they should not be pulling 12V off of that system anyway.
... need some 12 Volts to play the radio, run the CB for a short time OK. Like I said... you're the operator. Know your system, train for the mission.
If you have the trans and alt connected to the rear battery positive and do not disconnect the ground cable from that battery you still have 12V feed going to the alt and trans.I'am going to jump into the mix with another way to disconnect batteries... with an understanding that one does not want Mr. HumV to drain batteries when not in use, security concerns or hibernating for the winter.
Any truck, any transmission... remove the front to rear battery jumper. Place quality SPST disconnect switch ( see pix) to break the circuit between the front negative to rear positive. All 4 speed / 4L80 with a proper functioning distribution panel leave it factory for the 12 volt rear battery when that panel feed is connected to the rear battery positive. Also the 14 Volt alternator / equalizer feed at this connection. too. There should be NO drain on either battery. HumV now sleeping.
Those that have the need for 12 Volts to power external equipment... It's recommended practice to have the external 12 Volt buss fused and switched.
This becomes your "12 Volt Accessories Buss Disconnect" Doesn't have to be some 600 Amp big bucks switch when rated appropriately for the 12 Volt load needed. It will be up to the operator to understand the use of such arrangement. Think
Check the ratings of disconnect switch too. Most will handle holding current loads and one is not switching under high load.
There are many ways to handle this scenario. Sooo jump in..............
Space to earth... what's with all the switches in the Command Module... Houston.
No problem here, CAMO
This one gets it done, basic truck, no need for accessories 12 Volts.
View attachment 955832
This two pole can do both circuits when wired correctly.
View attachment 955831
Yes...
I see that the 12 / 14 Volts would be going to the alternator and the transmission controller. I don't have a 4 speed trans or dual alternator rig... SOooo you are right, that my suggestion / thinking may be flawed when looking for simpler disconnect...BUT on a 60 Amp / 3 speed truck it works. ... How does the alternator 12 / 14 Volt output load the terminal in question? Q2 the continuous 12 Volt connection to the TCM. What is it use for and its current drain. (leaky diode in the alternator or TCM keep alive circuit)
... guys looking to "CLEAR" any loading or drain on batteries are going to lift the positive and negative in the string and that isolation would do it... about the only way.... short (no pun) of removing the batteries Or the big expensive switch or switching arrangement with contactors to do the job. (still going to have to source contactor coil control to energize, requiring some rewiring. Aah the whole concept is rewire LOL.
, CAMO
