Power in Flux
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Thread: Issue finding proper relay/some motor capacitor questions.

  1. #11
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    Nov 2015
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    Quote Originally Posted by 4dollarjoe View Post
    See I've always wondered about that but I called alltrax and they said it was completely fine and it is their wiring diagram to just hook the ignition to the battery. I mean the thin wire acts somewhat as a fuse so is there really going to be that much current drawn to weld the contacts? When I took apart my bike a few weeks ago there was no signs of damage.

    Well... the wire itself should be fused. I think it was 5A, but my memory is fuzzy. The turn-on was essentially logic. I never measured the current, but I never feared that a generic 110v A/C switch would have trouble handling 90v DC at negligible current.

  2. #12
    Empulse R #24 frodus's Avatar
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    Aug 2010
    Portland, OR
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    110VAC, not 72VDC+ and DC voltage doesn't cross zero. Both current and voltage determine the size of an Arc. The higher the voltage, the longer the arc. The more the current, the wider the arc. Contacts for DC rated switches are made of different material that self extinguish the arc better and resist pitting the contact material. There can be a good size inrush on these controllers of several amps to precharge (like curtis and others that control their own contactor). It's not the wire, you'd have to physically disassemble the switch you're using at pack voltage and look at the contacts.

    Ever see a relay or switch rated for like 10A 110VAC but only 1A 24VDC? That's because they rate that switch life will be the best when not used outside those ratings. If you find a 150VDC killswitch, by all means do it. But I'd rather not have any pack voltage outside of the battery/motor controller circuit. Killswitch, ingition, they're all control power devices.

    Using the DC-DC that already has an enable is one of the better ways we've found to do the switching required, safely and to extend the life of all devices.

    Use however you want, Just wanted to put the disclaimer out there. I've got a background as an EE in Automation and control systems with a focus in power systems and we've discussed this many times on this forum and others.

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