A short while back I read a thread about where to install a battery disconnect. It seems to me there was discussion about the ground side or the "hot" side. I can't seem to find it. I would like to hear both sides again. I'm talking about a disconnect like the one pictured. Thanks.
I believe the NHRA requires the pos. side to be the one disconnected by the switch. I wired mine that way FWIW. Normal Norman
Switching the positive battery cable allows the alternator/generator to continue supplying power to the car. The fix for that is to either put the charge wire on the battery side of the switch, or get a switch that has a separate set of contacts for the alternator/generator charge(+) wire. Some of those switches have a current rating that is less than the starter draws. Although you can usually get by with it, if you don't have the switch yet, best sure to get one that's rated for what it's being asked to do.
I run them on the positive side because in the event of a short you want to be able to kill the current flow. All the cars and boats I have ever wired are done that way. Don
Ok, first, the reasoning behind switching the positive lead: If you get a short, and you "disconnect" the ground, you have not fixed anything. The short becomes the ground. Second, these switches are usually rated 300 amps, with a very high intermittent load rating to cover for starter usage. That only plays into it as long as you don't have to crank excessively. You do need to connect the charge wire to the car side of the cutoff switch, or as pointed out above, it will keep running.
And always shut the motor off before shutting the battery disconnect switch off. Otherwise, you can damage the alternator. Don
I will take the socratic approach and rather than explain how it works, I will ask a question to the select few that demonstrated inaccuracies in their idea of how one works. If you disconnect the ground, and there is a short in the cars electrical system, why do you think the short will become the ground? Were is the current flowing when the negative cable is disconneted? Is it going into the actual ground (dirt)? Sorry if I sounded like a dick, or still do... I'm bored and washing clothes for Viva Las Vegas tomorrow.
A simple YES or NO, will this Pollak switch work on my Roadster project, or did I piss away money on my first electrical part? Bob
you can come up with a case to make both ways look best, but in the end it don't make enough difference to matter. either one does the job. switch is fine 37
Those battery isolation switches are great insurance for your hot rod, consider a fire extinguisher as well. I isolate the earth side as per an earlier explanation. I am sure either side works better than nothing. I use the RED removable key type so I can take the key with me when locked up. I know it is only a soft anti theft effort but again better than nothing.
I have wired it on the ground side in both my trucks. I had it wired on the positive side at first and have a pile of alternators with burned out diodes to prove it. I admit to being "lost at sea" regarding electrical issues. I also note that most procedures regarding the battery instruct you to remove the ground terminal first and connect it last. Why is that.
ONE more YES or NO answer what wire/cable does the disconnect switch attach to + or - and IS THERE a differance with 6 and 12 Volt systems? BONUS question, why does REBEL WIRE offer LEFT and RIGHT hand drive wiring kits? Bob
There have been opinions offered in this thread for both positive and negative side installation, 6V or 12V shouldn't matter, and the bonus, I'd guess it's because the harness is engineered for position of steering column and switches and possibly fuse box. Sent from my DROID device using the TJJ mobile app
Our old Charger had that on the back ( Drag car ) , though if a short or anything was going on think by the time you got to the back of the car, damage done
Use a metal wrench to loosen the terminal. If you: A: Start at the positive, and touch any grounded metal part around the battery with the other end of the wrench you have made a short curcuit. Most of the car is grounded, so this is VERY likely to happen. B: Start with the negative: No danger if you touch any other grounded metal with the tool, since both the negative terminal and the rest of the car both are negative (or at least, not positive). The only thing that will make a short is if you manage to reach the positive terminal with the tool as you unscrew the negative terminal. Once one terminal is disconnected a short can only happen by touching that terminal with something connected to the other. Putting the breaker on the positive or negative lead does not matter very much, but it has some significance. If the circuit is broken, the circuit is broken - nothing can happen there anymore. You still have a live wire from the battery to the breaker ofcourse, so it should be as near the battery as possible, securely mounted and well insulated. Breaking the negative does have one advantage - if the breaker connections is shorted to the body or other grounded parts, nothing dangerous will happen since they are already supposed to be negative. If the positive goes through the breaker, and it touches ground in an accident or something like that... BBQ-time!
You disconnect the ground first and reconnect it last because if your spanner slips while you are tightening the battery terminal and you touch the body, you can't get a short circuit, thereby welding (or worse) your spanner to the frame. It also gets REAL hot quick too.
Yo, Socrates....... I see your point about the incomplete circuit when the ground post is effectively disconnected. I actually DO understand how all this works,...Hell, I taught it 40 years ago and within the last week posted (accurately) on a thread on a related issue. I have deleted the erroneous post. My excuse, if I need one (and I do ), is failure on my part to think it through to it's logical conclusion as I apparently have (had) a bias to interrupt the positive side. My brain short circuited.......... Ray Edit: just read G-Son's explanation and THAT also was humbling because it is EXACTLY what I have been doing for many, many years when changing a battery for the very reasons he mentions. I have to ask myself WTF was I thinking when I weighed in on this subject. Dang!!
I wire mine in the positive cable so that it DISCONNECTS the battery from the car. The main wire from the alternator to the battery can be shorted out and since the battery is the source of the power it is no longer connected to the car there is no problem. If it was in the negative side, any short on the positive side can still burn the car down because the source of the power (the battery) is not isolated. That's my theory and I'm sticking to it.
I'll be installing mine on the positive side, which will be the ground side of my system. Sent from my DROID device using the TJJ mobile app
Please give us a step-by-step explaination of what way the current goes from the batteries positive terminal to the batteries negative terminal, when a switch on the negative wire has disconnected the negative terminal from the rest of the car. No completed circuit? Then, no current.
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