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Thread: Kill Switch...because I believe in over kill.

  1. #1
    Constant Bitrate
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    Kill Switch...because I believe in over kill.

    I am looking for a switch that I can put inline on my 2 gauge power line. has anyone every done it?

  2. #2
    Maximum Bitrate rray's Avatar
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    I never have, but I just seen a car battery cutoff switch at Harbor Freight that would do the job.

    Sent from my SCH-I535 using Tapatalk 2

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    Super Moderator. If my typing sucks it's probably because I'm driving.... turbocad6's Avatar
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    use a circuit breaker, the resettable kind... you can trip it at any time to open the circuit, like a switch. this is the most compact way to switch this, and it also adds the necessary protection that you would have otherwise had to use a big fuse holder anyway


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    FLAC SNOtwistR's Avatar
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    Big rigs and heavy equipment use a master disconnect switch. I think you will need something like that for that 2 gauge wire. SNO
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  5. #5
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    Quote Originally Posted by turbocad6 View Post
    use a circuit breaker, the resettable kind... you can trip it at any time to open the circuit, like a switch. this is the most compact way to switch this, and it also adds the necessary protection that you would have otherwise had to use a big fuse holder anyway

    I have one of these up under the fender. It's not easy to get to per say, but it works
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  6. #6
    Raw Wave
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    Ah - a favorite topic... of mine.

    Do you mean kill switch, or isolation switch? The two are very different and cannot be combined (safely) with a single switch.


    I assume you mean an isolation switch.
    The best is a switch in the battery's -ve/ GND lead. That's best because it can be located anywhere on/in the vehicle without safety issues if the battery cable gets pinched and shorts to chassis or the bonnet shorts to the battery +ve terminal. (That's an important issue for competitive vehicles that require isolation switches in case of accident. Most are required to be cabin mounted in reach of the driver, and some require an additional switch at one rear corner of the vehicle. And I note with amusement that few prohibit +ve isolation LOL!)

    For non-competition purposes there are more options. Because the starter or alternator an other loads may be acceptably left connected, a smaller switch can be used in whatever +ve feeds are desired.
    The -ve/ground version is generally only suitable to switch ALL -ve/gnds from in the battery -ve terminal. It hence has to be rated for starter motor currents plus other loads. (You never want to break just one ground in a multi-grounded system - eg, battery -ve to engine to body, amplifier of HU power GND, CPU GND etc. Alternate ground paths with blow circuits, burn cables & tracks, fuse throttle cables, etc.)

    For +ve switches, I like the thought of the circuit-breaker types.
    For GND and competition use, it's usually the plain $20 isolator switch.


    Now, as for kill switches....

  7. #7
    Constant Bitrate
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    I would like to have the ability to shut of the power to that line completely is what I am looking to do

  8. #8
    Raw Wave
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    Ok, an isolation switch, for specific loads, hence +12V switching.

    There are lot to choose from including those pictured above. Even relays could be used (especially for automated or timed or low-voltage-cutout disconnection).

    A common type of switch used for competitions is:

    .. but many variants exist.


    The main thing is that the switch has a current rating higher than the fuse your are using for that line (I assume 150A - 200A for 2G?).
    And beware peak current ratings as opposed to constant current capability.

  9. #9
    Fusion Brain Creator 2k1Toaster's Avatar
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    You don't want to put a switch that you physically flip directly in line with the main power. That is just bad mojo waiting to go wrong.

    Put a switch that controls the coil of a relay. The extra 20mA of current draw is well worth the protection of the switch. And if you are planning on using the switch as a plug/unplug, then you could wire it so that the normally closed powers your system and when you flick the switch it disconnects and the relay conducts. That would be the best in terms of power saving, but backwards from what people would expect.

    This also gives you the ability to use a good high quality relay and and cheap crappy switch. The benefit is that the switch can be a very small but awesome looking switch instead of one of the very few able to switch the power required for your whole system.
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  10. #10
    Raw Wave
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    Not that I disagree - I too usually always suggest relays hence eliminating big switches and minimising voltage drops as well as have a large selection of switches, and inputs (FusionBrains, PCs etc).

    IMO it comes down to the application. Presumably it's for audio or other accessories, a suitable relay/contactor.is appropriate (no matter how it is controlled).
    But if to isolate a main supply (as in competition) or to disconnect something normally powered, then a switch is probably more appropriate - eg, manual switch(es) to isolate parallel batteries instead of battery isolator relays.
    (Al I know is it's a 2G cable, not it's function.)

    But a switch is advised (read: is used except in complex redundant relay implementations) where relay opening or failure is critical (eg, main power; maybe beams).

    If it's audio that does not have to be isolated frequently, then a switch. If power is only required when in operation, then a relay.

    FYI - relays can bounce. Hence not used for "competitive" main-power isolation except when considered reliable enough; usually requiring redundancy and known-spec components (G-forces etc).
    Last edited by OldSpark; 04-14-2013 at 04:08 AM. Reason: Tidied up a bit.

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