Power: Inverter, Switch, battery connection

bombboyer · 09-30-2002, 09:04 PM

Here's the deal. My cig lighter socket gets no juice unless the ignition is in the "acc" position, so it's kind of hard to leave the computer on if I just want to run in to pay for gas or something. So I'm thinking of connecting the inverter (300w) directly to the battery. What gauge wire should I use? And if I chop the cig plug off the inverter, how do I know which wire connects to + and which is ground or negative or whatever? I don't have a multimeter.

Also, should I buy a Optima Yellow Top (deep cycle) battery for this, or is my stock battery fine?

It's a 1999.5 Nissan Pathfinder SE. Is there any way that I could rewire it so the lighter socket always gets power? I would much rather do this than chop up my inverter. Then I was thinking that I could just put a switch on the + wire to turn it on and off (computer is set to auto-on when it gets a current in the BIOS).

Also, what's the volts, amps, etc to a lighter socket?

Need these answered too:

ok, stupid question: The fuse goes on the positive wire right?
Another very stupid question: Does the other wire go to the negative terminal or ground on the car body?

A not quite so stupid question: To avoid any 'buzzing', I just run a wire from the casing of my PSU to the case, and from the case to the cody body?

As you can see, my expertise is in computers, not electronics, or even basic circuitry

THEMP3KID · 09-30-2002, 09:37 PM

Not sure what gauge wire you should use, but 25amps should be enough, 8gauge is rated at over 50amps, so, that is probably an overkill... The wire that connects to the centre pin of the ciraret lighter plug is positive, the wire may aslo have a line on it, or be coloured red... Your existing battery should be fine... The volta to a cig lighter socket is normally about .5 or less volts less that the battery voltage due to losses in teh wire/fuse. this is 8-14volts or whatever.... The amps would normally be 10-30 probably, it has a fuse, read it and see what it is...

Mad Jad · 10-01-2002, 03:21 AM

Use 8-10gauge wire. Put a 20-30amp fuse within 6inches of the battery + terminal. Be careful though with the inverter as it draws a lot more power than you would think. Leaving it to run off the battery rather than alternator may not be a good idea; a couple hours and your battery will be dead

Thanks,
Jad

bombboyer · 10-01-2002, 09:14 AM

Any idea of how to rewire so the cig lighter always gets power? Can I just reroute the wires from the back of the socket to the battery terminals? Or do you think the car will have a problem with that.

mp3hombre · 10-01-2002, 11:20 AM

Yes it can be done but I'd rather wire the inverter directly to the battery. Many members have reported problems when using the cig lighter socket

Electronicsuk · 10-01-2002, 12:19 PM

If you are concerned about chopping off the plug then just buy a cigarette lighter socket and put it in a plastic box. Wire into the back of this through a fuse and then to the battery, as others have described in this thread.
Best regards,
Matthew

albysure · 10-06-2002, 08:03 PM

i've been wondering the fuse question for awhile myself. i will be wiring up my keypower supply and will measure the amp draw with all my stuff running. i was in touch with the keypower tech in ca a few weeks ago and he said he didn't know what size fuse to use. right now i a have a 20a in there.
i'll report back soon on what i measure

bombboyer · 10-17-2002, 10:10 PM

ok, stupid question: The fuse goes on the positive wire right?
Another very stupid question: Does the other wire go to the negative terminal or ground on the car body?

A not quite so stupid question: To avoid any 'buzzing', I just run a wire from the casing of my PSU to the case, and from the case to the cody body?

As you can see, my expertise is in computers, not electronics, or even basic circuitry

Thanks for the help.

MP3DUB · 10-17-2002, 11:02 PM

The fuse needs to go within the first 8? inches of the wire run from the battery on the positive wire. The ground just needs to go to the body, anywhere you can get a good (no paint, bare metal) ground. A self tapping screw works well for this. And grounding the case of the computer to the same spot helps with noise in the system.