Wiring power invterter to only power up when car is on?

[AltarCrystal 10+ year member]

Alright, got my hard drive installed Sunday, and must say, I freaking love it.

Only problem is, the power inverter I got constently has power even when the car is off, as it's wired in with a cig lighter.

Here's how I set it up.

I bought a 12v socket, you know, cig lighter style. I wired this in line with an existing cig lighter. I ran that to the glove box. The inverter plugs into the aftermarket cig lighter, and the HD plugs into the inverter.

Since it's a temp set-up until I get my sub box and amp rack built, this is all in the glove box right now. Problem is, I have to unplug it everytime I get out of the car, and plug it in everytime I get in.

I'd really like to have it turn on with the car, and off with the car. I'd really like to avoid any kind of switch.

Any ideas?

EDIT: Forgot to mention, I found that most my fuses are getting constent power. I'm still looking, but I've got the whole fuse box under the dash to go. Maybe wire it in-line with the +12 for my HU?

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[mokedaddy 5,000+ posts]

Two ways to do this. Either wire the aftermarket socket to the ignition wire on your vehicle. This wire can be found in the ignition harness under the driver's side dash. Or you can cut out the aftermarket socket and cut the end off the inverter and hardwire that directly to the ignition of the vehicle.

 

[AltarCrystal 10+ year member]

Alright, would it work if I find which wire is the ignition wire on my hu's wiring harness, and splice into that? Then use the harness's ground for it's ground?

 

[jdawg 5,000+ posts]

how much does a hard drive draw? I would use the switched lead to your hu as a trigger to a 30 amp relay, wire the relay directly to the battery and wire your power inverter to the relay

 

[uPsDdOWN 10+ year member]

sorry... wrong...

The right and safe way to do this is wire the Inverter through a hi amp, normally open relay. If you can find one with a built in Diode, it would be best to prevent voltage surges to your p/c.

Like one found here: http://www.wiringproducts.com/?target=dept_36.html&gclid=CLDj-cuEjY0CFRtzhgodXGrZkQ

Then, use and ignition source (+) power lead to trip the relay when you turn it to the on position.

 

[mokedaddy 5,000+ posts]

May I ask how that is safer than pulling low current from the ignition harness? If fused it is just as safe and much less work than wiring to the battery with a relay. If it was for something high current than yes your way is the much better way but for something low current such as a HD there is no reason to go the extra mile. But of course it wont hurt if you decide to do that as well.

Also if you use a relay a normal everyday 30 amp one will do the trick.

 

[AltarCrystal 10+ year member]

Well, the HD only does about 500mA, so it's hardly pulling ANYTHING. 7-8 watts on a 14.4 voltage (If my education is correct, here) correct?

Is it safe if, like I said, wired the + wire into the ignition wire for my harness, and the - into the ground for my harness?

 

[DTK 10+ year member]

honestly the right way to go is using that relay

 

[uPsDdOWN 10+ year member]

Lets do the math-- the average Laptop computer draws about- say, 75-80 watts.. at full operation... ALLWAYS double that for the automotive environment- that takes us to 160--- since they dont make a 160 W Inverter--lets jump to next avail size.. 250 W 12V DCV to 110V AC.

At this rate the input will be 30 amps. This requires a large cable, 8 to 10 AWG, or bigger, and as short as possible. Dc is ineffecient. The wire under the dash is usually 14-12.

You are drawing TOOO much current = heat. Don't do it, buy a relay, prevent a meltdoown in the fuse panel, or worse, a car fire.

be smart about it, you don't wan't fluctuating power to an electronic device like a computer-- your asking for problems.

 

[AltarCrystal 10+ year member]

Lets do the math-- the average Laptop computer draws about- say, 75-80 watts.. ALLWAYS double that for the automotive environment- that takes us to 160--- since they dont make a 160 W Inverter--lets jump to next avail size.. 250 W 12V DCV to 110V AC.
At this rate the input will be 30 amps. This requires a large cable, 8 to 10 AWG, or bigger, and as short as possible. Dc is ineffecient. The wire under the dash is usually 14-12.

You are drawing TOOO much current = heat. Don't do it, buy a relay, prevent a meltdoown in the fuse pane, or worse, a car fire.

...but I'm not running a laptop, I'm running a hard drive...which draws like...8 watts.

 

[uPsDdOWN 10+ year member]

hey, you can do what you want.. Ima nobody. I just think your crazy to run it directly off an ignition wire. even the HD cannot handle a fluctuating current... you WILL be replacing it very soon-- if you do this, wiring it directly, then at least us a small cap.. in this situation, wired in series, it will at least act as a buffer and hopefull protect the HD. It is an AC component, probably designed for 60Hz operation... which is relatively steady in home a/c.. NOT in a car, with all the other acc, lights, stereo. I think you are asking for problems. Go ahead and take the cheap way, but be sure to let us know when it fries the HD. -- Im out--

 

[AltarCrystal 10+ year member]

hey, you can do what you want.. Ima nobody. I just think your crazy to run it directly off an ignition wire. even the HD cannot handle a fluctuating current... you WILL be replacing it very soon-- if you do this, wiring it directly, then at least us a small cap.. in this situation, wired in series, it will at least act as a buffer and hopefull protect the HD. It is an AC component, probably designed for 60Hz operation... which is relatively steady in home a/c.. NOT in a car, with all the other acc, lights, stereo. I think you are asking for problems. Go ahead and take the cheap way, but be sure to let us know when it fries the HD. -- Im out--

I didn't say I was refusing the idea of a relay, you just went off using a whole laptop as an example, when I'm only running a hard drive.

 

[mokedaddy 5,000+ posts]

I will say this, the "right" way is subjective. Yes it best to run it to the battery with a relay turn-on. But if the electrical system of the vehicle is up to par it is "acceptable" practice to wire a low current device off of the ignition wires. It is up to you but most people will wire it to the ignition because they are lazy or extremely busy. I have seen it work in most cases and have even done this myself with no problems.

Its kind of like grounding an amplifier. Yes it is best to run the ground back to the battery (path of least resistance) but most of the time it is perfectly acceptable to use a bare metal chassis ground.

 

[AltarCrystal 10+ year member]

Alright, I'll swing by AutoZone Thursday, see if they carry relays. If not, guess I"ll have to order one.

Basically how I understand it, is that's the + and the -, and then a third wire that's sort of a "remote" wire? Do I wire it in with the ignition wire then? Or the acc remote wire on the hu? Sorry, I've never wired a relay before.

 

[jdawg 5,000+ posts]

its on the back of the box, yes they carry them for way an overpriced amount, just get a universal fog light relay, those tards will hopefully know what that is