Is 30A fuse too much for carputer power?

**GFridrich3** · 09-16-2006, 03:24 PM

I know this is a "subjective" question, but hopefully there is a general rule of thumb that you experts know of to help the new guy out.

Ive done a bit of searching on the site, and have been lurking for a while, just signed up today thou.

I bought one of those universal "car amplifier" installation kits rated for 200w continuous power. In the kit it comes with an in-line fuse rated for 30A.

I will be using an M2-ATX power supply for my install and from what i can gather, it its rated for 15A. Also, I will be running my VGA screen independent of the carputer since i will also have a dvd player installed in the car for use when i dont need the entire PC on. Both will be powered from behind the 30A fuse, or the screen will be run directly from my switched accessory power (depending on what will be easiest for wiring purposes)

Is the 30A fuse provided in the pacakge a little too big? Do the experts here suggest I go to a smaller 20A or 15A fuse for safety? I dont want to go too small and end up blowing fuses under normal operating conditions, but at the same time, i dont want to let too much power sneak into my system and cause any damage. What are you experts using on your power lines to protect your systems?

Thanks for the help. And also, if any of you have a thread bookmarked that helps answer this, could you please hotlink it here for me? Id appreciate that.

Also, just want to say, being one of the new guys, i really appreciate all the information you guys have compiled here on the site, ive learned a LOT of things i didnt think i would need to know at first about building my own CarPC, and now several months later, im finally moving on to buying the parts and committing myself to the project. Hopefully i will have something useful to contribute someday to payback for everything ive learned from here so far.

**ming** · 09-16-2006, 04:03 PM

15A should be enough for most carputers. yes, a 30A fuse would provide less protection if your computer and monitor always draw less than 15A.

**GFridrich3** · 09-16-2006, 07:09 PM

Actually, i think when i re-read my question, i might be a little confusing.

1) CarPC will be powered from behind the 30A Fuse
2) VGA Monitor will be powered from behind the 30A Fuse
3) Portable DVD Player will be powered from behind the 30A Fuse

There are times i can see that i may have all 3 devices running at the same time, and times when they all may be turned off.

So really I have a 15A power supply, and 2 other power consuming devices that both may be drawing from that 30A source. Does this sound like a bad idea? Perhaps I should leave the 30A where it is, and tap into the main power line with smaller Amp Fuses to each individual device for what they are rated? Otherwise, i may be tempted to just tap into the stereo harness to power the screen, and the 12v outlet for the dvd player and use the new power line exclusively for the CarPC to make sure its getting all the power it deserves at any time.

**DarquePervert** · 09-16-2006, 11:07 PM

If you're going to fuse the line that powers all three devices, you should measure the current draw with a multimeter (in amps, of course), then get the fuse that is just above that current draw.

So if the total current draw is 13.7A, you should use a 15A fuse.
In that scenario, a 30A fuse would provide no protection for the electronics behind it.

From what you've stated you're going to need to protect with a fuse, I'm guessing that a 20A or possibly a 15A would be what you need. There's no way that the components you specified are going to draw anywhere near 30A

**pate60** · 09-17-2006, 04:25 AM

30A is overkill

**GFridrich3** · 09-17-2006, 08:46 AM

Thanks Darque, I guess the only way i will really know is once the stuff is ALL hooked up and ALL running at the same time. I guess ill start with a 15A fuse the first time i fire up the system in the car just to be sure. I think thou that since the PC is the critical one here im worried about, i may just leave the 30 where it is by the battery and install an extra 15A fuse to the line somewhere before it connects to the PC just to be safe.

Thanks for the help.

**jnorion** · 09-17-2006, 12:53 PM

You should probably put a separate fuse in for each component as well, if you think the power you draw might vary that much with what you turn on and off.

**GFridrich3** · 09-17-2006, 11:43 PM

Originally Posted by jnorion

You should probably put a separate fuse in for each component as well, if you think the power you draw might vary that much with what you turn on and off.

Thats what I was thinking of doing in my second post, about placing smaller amp fuses between each component and the main power line. I guess i just need to get everything and have it all installed so i can see what kind of draw its actually putting on the line.

**turbocad6** · 09-17-2006, 11:53 PM

the 30a fuse in the holder near the battery is to protect the WIRE, not the components.... if the wire got pinched anywhere or shorted to ground, this fuse will prevent your car from burning to the ground as the wire heats up red hot & melts the insulation, as well as everything else in contact with it, like carpet... etc...

each component should then be protected individually to protect the component... this is what fuse distribution blocks are generally used for... the 30amp fuse is fine at the front... & should be as close to the battery as possible because anything before the fuse is unprotected at all, kinda like the battery terminal itself...