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Some general electricity questions (relays, etc)

1841 Views 1 Reply 2 Participants Last post by  freeflubber
I have a 220W Power Inverter, switching from 12V DC to 115V AC (I think
that's standard, reguardless, not important...) Attached to that Inverter
will be a computer's power supply, which is rated at 200W (which means
it'll work just perfectly with this inverter, and it does, I've tested it
plenty of times before). But here's where my problem arises (haha, I said

The inverter has an on/off switch, which means if I leave it on, it'll
kill my battery(s). So I thought of lopping off the lighter plug bit and
just hooking it up to a relay. Then have the relay run directly to the
battery and the SIGNAL wire run to my ignition or some happy *********
like that (again, not important).

But..... I don't know what kind of relay to purchase. I found a website
called that has everything known to man there, including
all types of relays. The only variable is the Amps.... so now to my actual

What amperage should I get for a Power Inverter that's hooked up directly
to the battery? Would that be listed on my battery? Since I have TWO
batteries, wouldn't that change? Also, when set in parallel, extending the
wires increases resistance, which makes things superhot, so again,
wouldn't that be a factor? ******* electricity...

Remember, I'm going from DC --> AC, so the final product (in this case the
computer) doesn't matter. I only need to know the load that the relay will
be inputting... or something like that.</pre>
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The power rating from your inverter may be 220W, but the available power output of the socket is only 120W, if you require more than that you would need to wire direct to the battery with no more than a 20A Fuse. Your computer power supply probably draws considerably less than its maximum wattage rating.

As far as the relay goes, just make sure you use a relay rated for a 12V DC coil @ minimum 15-20 Amps contacts. Use wire of at least 10 gauge, and preferably 8 gauge, with this size, the length of wires will not cause heat. A socket mounted relay (with a socket) would make it easier to connect.

Good Luck!
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