View Full Version : Head unit power cable
How do i connect the uprated positive cable from the battery to the ISO block do i have to buy some pins?
And do i have to uprate the negative from the block as i was only given the postive cable.
Icecavern
23-04-2004, 14:05
Slightly confused. Why do you need uprated power and earth? Are you replacing the HU?
Yes got a alpine 4x60watt HU.
Do i need to uprate the ground cable or jus the positive cable. As the guy only gave me a positive cable!
Icecavern
23-04-2004, 16:21
Right I understand now...
You don't need to connect the power cable to the ISO block. If you look at the Alpine wiring you'll see bullet connectors that are between the HU to the ISO block. Just connect the power feed from the battery to this by pulling the bullets appart and connect to the HU side of the split.
Putting in a new ground might also be a good idea, but you don't need to take this back to the battery. Any good ground behind the dash is fine.
Pete
Thanks for the help!
One more question tho! What ampage of fuse should i use for the inline power cable fuse for an Alpine 4x60watt HU?
Icecavern
24-04-2004, 08:08
Whatever is on the back of the HU put the same fuse within 12" of the battery.
Pete
Thanks for the help!
One more question tho! What ampage of fuse should i use for the inline power cable fuse for an Alpine 4x60watt HU?
20A fues, no bigger! if you work it out, P = IV
P: 4x60 = 240
I: I
V: ~14V
therefor I = 17.14A
Thats just for the speakers alone, so another amp or 2 for the head unit running. Any more than than will mean that the headunit wont be protected if you put too much power down. I didnt fuse the cable again near the battery, i suppose i should have, however the cable you get with the HU has a fuse and an RF suppressor.
I ran a 2 core power cable for household use from the battery to the headunit. This meant i knew it could handle the power and as its binded together you only need to run 1 cable about the car, keeping it tidy.
Icecavern
24-04-2004, 15:15
Hang on one second...
THE FUSE AT THE BATTERY IS NOT THERE TO PROTECT THE HU!!!!!
The fuse is there to protect the wiring against shorting. Any power cable coming from the battery MUST be fused within 12", 18" max of the battery post. You have an unfused section of cable coming from the battery and through the firewall, which quite frankly is dangerous.
I also wouldn't be so sure about the cable you've used. Household cable isn't rated at high currents, it doesn't have to be because of the voltage. You only need the + from the battery the ground can be sourced anywhere under the dash.
Pete
True that, but at the same time, whats the point of making it any bigger than what is needed to protect the HU? With any luck you will pop just the fuse closest to the battery and so you wont have to take out the HU and get a new fuse for it.
The cable i used is rated for about 20 amps, and it double insulated and looks tidyer than a single bit of wire cutting about. I should fuse it, but didnt have a fuse at the time. just hope that the insulation stop its from bing damaged for the now. I also only run two speakers off it.
I would have used a ground under the dash, but its all plastic and it was easier to run it back to the battery than hunt about for some metal, bear it, drill it..... you get the pic.
The cable i used is rated for about 20 amps, and it double insulated and looks tidyer than a single bit of wire cutting about. I should fuse it, but didnt have a fuse at the time. just hope that the insulation stop its from bing damaged for the now. I also only run two speakers off it.
Domestic (household) cable is not much good for your car. Most domestic appliances only draw about 13A max, so as Pete says, its not needed to be rated for high current. My Alpine amp draws up to 30A max, so it needs good quality cable. I have 4awg cable for the power and earth. My power cable has a 40A fuse 3 inches from the battery and a 30A fuse next to the amp in the boot. The 30A fuse is there to protect the amp, 40A for the cable. They're necessary too as when I was installing the cable, I accidentally touched the cable on the body of the car. It blew the fuse, however if the fuse had not been theree, it would probably be bye bye battery :(