Splitting power - how much is too much?

**bmbr** · 06-16-2006, 01:46 PM

So right now I am using the power off of my old stock dash.. it comes in the form of (2) 14-16ga wires that I have extended to reach my psu. So far this seems to be ok, but I feel rather hesitant about putting too much power on this line.

Essentially, I need to cut my LCD cable and an external HDD cable and feed them power thru my truck, but I don't know that I should be doing it off of these 2 wires given their size. I intend to investigate into a direct battery line this weekend, but I'm still not sure how easy it will be to get past my firewall. But, for the moment let's assume that the wire size isn't an issue.. What is the best method to tap into this power?

Do I use some sort of a splitter that lets me tap into these lines? Or is it better to use something like an internal (4 prong mylex) power adapter off of my PC that has been cut and extended? Are these power lines 5v or 12v? Also, is there a "best method" for determining which side of the 2pair AC adapter (that im going to cut) is positive/negative before I cut it / does that matter in this case?

All in all I'm looking for a relatively easy solution that won't cause my truck to catch on fire =]

as always, thanks guys!

**Wiredwrx** · 06-16-2006, 02:05 PM

Originally Posted by bmbr

So right now I am using the power off of my old stock dash.. it comes in the form of (2) 14-16ga wires that I have extended to reach my psu. So far this seems to be ok, but I feel rather hesitant about putting too much power on this line.

Essentially, I need to cut my LCD cable and an external HDD cable and feed them power thru my truck, but I don't know that I should be doing it off of these 2 wires given their size. I intend to investigate into a direct battery line this weekend, but I'm still not sure how easy it will be to get past my firewall. But, for the moment let's assume that the wire size isn't an issue.. What is the best method to tap into this power?

Do I use some sort of a splitter that lets me tap into these lines? Or is it better to use something like an internal (4 prong mylex) power adapter off of my PC that has been cut and extended? Are these power lines 5v or 12v? Also, is there a "best method" for determining which side of the 2pair AC adapter (that im going to cut) is positive/negative before I cut it / does that matter in this case?

All in all I'm looking for a relatively easy solution that won't cause my truck to catch on fire =]

as always, thanks guys!

First, I assume you are refering to the power wires that are going/used to go to your HeadUnit. They can NOT supply enough power to your DC-DC PS safely. You MUST run power to the battery. This is not hard at all. Every car has things that come into the car from the engine. They ALL have a rubber "boot" that you can cut slightly, and pull the wires through. EVERY CAR. Yours is no different.

Next, what do you mean "I need to cut my LCD cable and an external HDD cable and feed them power thru my truck" Your LCD should be powered from your DC-DC PS, and not directly from the truck. Also, what is your "external HDD cable" That makes no sense to me.

Are WHICH power lines 12v or 5volt? What are you talking about.

What 2 pair AC connector are you talking about?

It MIGHT be time for a rpofessional, or at least someone that knows what they are doing to wire your truck for you.

Michael

**TheLlama** · 06-16-2006, 02:16 PM

I would run another wire from your battery. If you don't need it now, you will later.

**bmbr** · 06-16-2006, 02:21 PM

Originally Posted by Wiredwrx

First, I assume you are refering to the power wires that are going/used to go to your HeadUnit. They can NOT supply enough power to your DC-DC PS safely. You MUST run power to the battery. This is not hard at all. Every car has things that come into the car from the engine. They ALL have a rubber "boot" that you can cut slightly, and pull the wires through. EVERY CAR. Yours is no different.

my car isn't a unique and beautiful snowflake? Good to hear though, I will do that this weekend.. when I do, is there a specific gauge of wire I should use (will 10-12 be enough?)? If I'm doin it I might as well do it right.. oh, and while we're at it, have you seen any nifty diagrams/pictures layin around on the interweb that explain how to hook it up? I'll google shortly as well and post any results i find...

Originally Posted by Wiredwrx

Next, what do you mean "I need to cut my LCD cable and an external HDD cable and feed them power thru my truck" Your LCD should be powered from your DC-DC PS, and not directly from the truck. Also, what is your "external HDD cable" That makes no sense to me.

Are WHICH power lines 12v or 5volt? What are you talking about.

What 2 pair AC connector are you talking about?

Sorry, I knew that part was going to be confusing.. My LCD Touchscreen has a cig lighter power adapter that I need to cut and wire into my PSU or ACC power so it turns on with my truck. My external hdd is a usb2 enclosure that also comes with an AC adapter that I intend to cut and hardwire into my PSU or ACC (whichever is best, but I don't know that I want to put anymore strain on my psu).

the 12v and 5v lines I was referring to are the internal 4prong mylex cables that come off the PSU to provide power to internal drives, etc.

and the 2pair I was talking about are from the actual AC and cig adapters for said LCD and USB hdd.

Originally Posted by Wiredwrx

It MIGHT be time for a rpofessional, or at least someone that knows what they are doing to wire your truck for you.

Hey now, there's no need for that kinda language!

**bmbr** · 06-16-2006, 02:24 PM

Originally Posted by TheLlama

I would run another wire from your battery. If you don't need it now, you will later.

As in, you suggest that when I run my wires from my battery, I bring an extra set along with my primary 2?

**Wiredwrx** · 06-16-2006, 02:35 PM

Originally Posted by bmbr

Sorry, I knew that part was going to be confusing.. My LCD Touchscreen has a cig lighter power adapter that I need to cut and wire into my PSU or ACC power so it turns on with my truck. My external hdd is a usb2 enclosure that also comes with an AC adapter that I intend to cut and hardwire into my PSU or ACC (whichever is best, but I don't know that I want to put anymore strain on my psu).

the 12v and 5v lines I was referring to are the internal 4prong mylex cables that come off the PSU to provide power to internal drives, etc.

and the 2pair I was talking about are from the actual AC and cig adapters for said LCD and USB hdd.

Hey now, there's no need for that kinda language!

No need to find a diagram, though it might help. Just look up towards the firewall from where the pedals are, and you will see several things that go through the firewall. Just make sure there is nothing moving thorugh the firewall (like the clutch pedal, brake, or sterring column, though you "could" use them).

As for the LCD, power it from the PSU, not the accessory. Yes, this MIGHT tax your PSU, then get a better one. Sorry.

Does the USB enclosure also have a USB power cable, or have a dual usb cable with it. if so, you can power it from the 5 volt rail of your PSU. You probably CAN NOT power the USB straight from the car, no matter where you cut the ac cable. Car voltage varies from 10 to 14 volts or thereabout. Even if your USB operates from 12 volts, your car will not maintain that voltage the whole time. If it is 5 volts, well then, you see the problem I hope.

The language was just a warning. If this is over your head, you don't want a smoldering heap of a pickup, do you?

Make sure you fuse everything correctly. You really should read the faq section about wiring your car and computer.

FAQ: Connecting your Car PC's Power and Speakers

http://www.mp3car.com/vbulletin/showthread.php?t=76241

Good luck.
Michael

**TheLlama** · 06-16-2006, 02:35 PM

Originally Posted by bmbr

As in, you suggest that when I run my wires from my battery, I bring an extra set along with my primary 2?

No, I suggest running a single power cable that can provide enough power for all your components and then some. For example, if you find you need 14awg, install 10awg. I wouldn't run your ground from the battery, you probably have a better groundpoint near your dash.

**bmbr** · 06-20-2006, 06:15 PM

I was able to do this over the weekend with great results.

To begin with, yes, running a cable thru the firewall is VERY easy and definitely worthwhile. Once I brought mr 4ga cable inside of the cab I connected it to a "Power Distribution box". This one was made by Monster, but you can find cheaper versions of it at stores such as Pep-Boys.

From there I ran 10ga wires to my LCD and to my M2-atx with no problems. I brought their Negative ground lines back to the same point and everything powers fine (though unfortunately it did not remove whatever is causing my alternator hum...).

As to my other question regarding the Molex adapters... on each hdd power adapter from the PSU there are 4 lines. Red/Black/Black/Yellow. Red/Black are your 5v lines and Yellow/Black are your 12v lines. I was able to splice into an unused one, pull the 12v and connect it to a cut power adapter that is used to power my external hdd. Now it all comes right off the PSU as I had hoped.

Hope this helps someone else!