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| Cut off switch - which terminal? https://www.ausmini.com/forums/viewtopic.php?f=2&t=28582 |
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| Author: | miniclubbhoy [ Tue Feb 27, 2007 8:58 am ] |
| Post subject: | Cut off switch - which terminal? |
Ok, electrics are NOT my thing 
I have a cut off switch for my battery as it keeps draining on me after a few days if i haven't been driving. It looks like this... http://cgi.ebay.com.au/eazy-battery-ter ... dZViewItem Does it matter which terminal it goes on? Sorry for the dumb question (i can change a lightbulb but that's about it!!!) |
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| Author: | sports850 [ Tue Feb 27, 2007 9:02 am ] |
| Post subject: | |
On the positive terminal normally , but I'll wait and see what the sparky's say out of interest too . |
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| Author: | Harley [ Tue Feb 27, 2007 9:04 am ] |
| Post subject: | |
You'd think positive, but whenever working on a car involving electrical things, manuals always say "disconnect the negative/earth terminal". I really dont think it matters. 
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| Author: | Angusdog [ Tue Feb 27, 2007 9:31 am ] |
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If you disconnect the negative (earth) cable, then it won't matter if you connect a tool to a wire and the body at the same time, as the body won't carry the current back to the battery. This is why when disconnecting the battery you should remove the negative cable first. If you try to disconnect the positive cable and your wrench swings round and touches the body, it will arc, spark and generally be bad, as I have learned... Incidentally, I believe you can run a fused wire around the killswitch to carry enough current to keep your stereo security PIN number etc, but when someone trys to start it, the fuse will blow. Obviously you'll blow about 20 fuses before you remember to check the kill switch before trying to start your car. |
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| Author: | sports850 [ Tue Feb 27, 2007 10:04 am ] |
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This is why I wasn't going to definitely say the positive cable ... Most car's I've seen them (battery isolaters I mean more than this type of cutout) have them fitted to the positive (or non earth , depending on whether it's a generator or alternator ...) , but as said above you remove the earth cable first to disconnect the battery when working on the car or anything ... Gets confusing really . |
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| Author: | Hanra [ Tue Feb 27, 2007 10:10 am ] |
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Either or, it dosnt matter. Either terminal being open circut will stop current flowing from the battery. |
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| Author: | VicMini13 [ Tue Feb 27, 2007 10:35 am ] |
| Post subject: | |
If you want to use the Isolator as a cut out switch too - it needs to go on the positive, and the charge wire from the alternator will have to move to the battery side of the switch, otherwise if you isolate the battery while the engine is running it will continue running on the power supplied from the alternator charge circuit. Go to a historic race meeting and look st some Group N Minis and chat to their drivers/mechanics. |
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| Author: | Mick [ Tue Feb 27, 2007 12:05 pm ] |
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Trouble with the negative from the battery, is that it's only 30 centimeters long, you wouldn't need to search very far to find it. Mind you, they would be searching the +ve wire as the most obvious place. You could extend the -ve out under the car somewhere and earth it via the switch somewhere sneaky. |
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| Author: | 1360 LS [ Tue Feb 27, 2007 12:10 pm ] |
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If the electricity doesn't loop back which it won't then positive or negative terminal don't matter, just don't touch both at the same time because you'll be the one completing the circuit ..... then u go fry fry!! |
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| Author: | slinkey inc [ Tue Feb 27, 2007 3:50 pm ] |
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Most people I know go for non-earth as it travels the length of the vehicle. I used that. And I have a small, circuit breaker fitted wire for radio. But it has never blown when starting with battery off. There is no ignition, so power to the solonoid, is not there. The power to it direct is from battery to radio. But now I got an immobiler which is better anyways. SO the cut off is for emergencies and for working on the car. As an aside, the most dangerous problem with mini electrics, is an uncovered battery. All you need is a tyre iron, or similiar to fall across both terminal, and then large current flows due to lack of resistance, forming what we know as a 'short circuit' not good. Can start a fire! I got covered connectors on my car. Only thing is that you can't jump start it as you can't connect onto the battery while another connector is already there. But who needs to jump start, when you can push start a mini! |
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| Author: | Mike [ Wed Feb 28, 2007 2:13 am ] |
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VicMini13 wrote: If you want to use the Isolator as a cut out switch too - it needs to go on the positive, and the charge wire from the alternator will have to move to the battery side of the switch, otherwise if you isolate the battery while the engine is running it will continue running on the power supplied from the alternator charge circuit.
This seems a strange advice (or am I not getting something?). To "isolate the battery with the engine running" with one of these switches you'd have to physicaly screw out the knob and remove it while the engine is running. This is a pretty unreasonable thing to do anyway but if you did this the low amperage fuse that bypasses that knob (this is if you indeed set it up with a fuse so as to act like a cut off switch like was suggested before) will either blow because of the drain of the ignition and headlights and then everything will die or if the fuse is higher amperage and the headlights are off then the charging circuit to the battery will be maintained through that fuse. The idea of the cut off switch on the isolator is that a fuse will power auxilaries with the engine off and the isolator switched off but will burn out when one tries to crank the engine over to start it without screwing the isolator knob back in (as the drain then will burn any fuse thinner than a nail). Not that the fuse will burn with the engine running. |
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| Author: | VicMini13 [ Wed Feb 28, 2007 7:02 am ] |
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Hi Mike, I was thinking more along the lines of the isolator type cutout switch that they use on race cars so that in the case of an accident all you do is pull the pin to stop the engine (and everything else electrical like fuel pumps) and isolate the battery. |
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| Author: | miniclubbhoy [ Wed Feb 28, 2007 8:56 am ] |
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Thanks guys, I installed it on the negative last night and it works fine. I only want it so that i can isolate the battery when i'm not using the car to stop it going flat. I think i need to go out and get a book on electrics for dummies as there was a fair bit of that discussion I didn't get! Cheers. |
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| Author: | Razor [ Wed Feb 28, 2007 2:54 pm ] |
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I've heard of bad things about that cutoff switch, they sometimes fail not really reliable. Can someone confirm this? as I've got one on the shelf |
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| Author: | slinkey inc [ Wed Feb 28, 2007 3:50 pm ] |
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They seem to wear out, but when on they stay on, but when off they can be hard to turn back on. Well in my experience so far. |
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