Power and wiring with an M2-ATX.

**Mrcat88** · 06-24-2006, 08:51 PM

Hi all.

I did search, before anyone gets their panties in a knot.

I have run 4g wire from the battery to a distribution block...a nice one. I ran an 8g wire over to where the carputer is going, and I was planning on using it for power, along with an 8g ground, switched from the same wire as my deck.

I also plan to run an amp in the future, not sure what, but I have open 4g terminals as well as multiple 8g terminals.

Here are the questions:

1. I have a nice 100Amp circut breaker...should I make use of this between the distribution block and the battery? Would it be wiser to go with a fuse instead? Why? If I get a fuse, what amperage should I put in there? (I know it's according to my needs, but I figured with everything fused already, just add the circut breaker for protection of the DB.)

2. Is 8g too much to power a modest pc running off of an M2 ATX? Should I step it down....or does it matter, assuming I can connect it to the M2? I don't see how it matters, although I know there is a 15 amp fuse on the M2...will I just blow it right away? This leads to the next question....

3. Should I put a fuse inline on the 8g before the M2? Does the 15 amp fuse on the M2 cover this, or is it to serve a different purpose?

Thanks in advance for any advice here. I just want to make sure my wiring is set while I am waiting on the M2 to show up.

**v8 scimitar** · 06-25-2006, 06:31 AM

I have no idea what 8g 4g is as we use mm so cant help with fuse ratings but I can with position. Fuses are there to protect the cable not the apliance as they have their own just like your M2 has a 15A on the board, this is for the M2 and wont protect your cable. You must fuse at the start of any cable run. So from battery to DB you need a fuse at the battery form DB to powersupply it needs to be fused at the DB if the DB doesnt already have fuses built in. Reason being if something hapens the the cable, say the cable got traped and shorted to ground just before the power supply it wouldnt be protected by the M2 fuse so it would go on fire if the short was bad enough.
Hope that makes sense to you if not then just shout and I will try and explane a bit better.

**DarquePervert** · 06-25-2006, 07:39 AM

Originally Posted by Mrcat88

Hi all.

I did search, before anyone gets their panties in a knot.

But knotted panties are sooooooo kinky.

1. I have a nice 100Amp circut breaker...should I make use of this between the distribution block and the battery? Would it be wiser to go with a fuse instead? Why? If I get a fuse, what amperage should I put in there? (I know it's according to my needs, but I figured with everything fused already, just add the circut breaker for protection of the DB.)

A circuit breaker functions the same as a fuse. A fuse has to be replaced. A circuit breaker can be reset. The circuit breaker should be fine.

2. Is 8g too much to power a modest pc running off of an M2 ATX? Should I step it down....or does it matter, assuming I can connect it to the M2? I don't see how it matters, although I know there is a 15 amp fuse on the M2...will I just blow it right away? This leads to the next question....

It will provide plenty of power for your PC. It might be overkill, but in this case it's not a bad thing.... The thicker wire will reduce the possibilty of your system being underpowered. It will also create less heat.

3. Should I put a fuse inline on the 8g before the M2? Does the 15 amp fuse on the M2 cover this, or is it to serve a different purpose?

The fuse on the M2ATX is to protect that device. I would put another 15A fuse ont eh 8awg line from the distro block to the M2ATX, assuming your distro block doesnt have fused outputs. If it has fused outputs, then just drop a 15A fuse in the output to the PC.

**Mrcat88** · 06-25-2006, 10:55 AM

I have no idea what 8g 4g

I was just saying 8 guage and 4 guage...sorry, I was tired. I understand where I should idealy have a fused connection, and I want to isolate the DB and everything on it with a fuse as well (or breaker). I am only running the puter on all of this right now, so I don't have huge power demands at the moment. I plan to add more later, and will upgrade the fuse accordingly.

The fuse on the M2ATX is to protect that device. I would put another 15A fuse ont eh 8awg line from the distro block to the M2ATX, assuming your distro block doesnt have fused outputs. If it has fused outputs, then just drop a 15A fuse in the output to the PC.

So the fuse on the M2 is only for the device....but why would I want another of the same fuse on the line....to protect the wiring itself? My block doesn't have fused outputs...just connections.

I think 100 amp breaker will be much overkill at present, with the computer the only thing running...and I don't think I'll ever get enough in the car to use that kind of power. A friend and I worked it out last night, and we decided that with the PS, and a 300 watt amp (or around there) I could use a 40 amp fuse and still be safe. My car is a 2 seater, very small....I can't add much more. That 40 is with the other devices fused as well.

I was under the impression that the fuse on the M2 would protect itself and the line, but I don't know why I was thinking that. I am starting to understand why you say to put another on the line. I just didn't want to overpower the M2 or fry it.

So for now, with only the DB and computer, you guys think I could go with a 20 amp fuse/breaker between the batt and DB, and a 15amp fuse on the computer line....and that's it, so far. Up the amperage of thje main fuse later?

Thanks alot for the help!

**DarquePervert** · 06-25-2006, 11:25 AM

Originally Posted by Mrcat88

So the fuse on the M2 is only for the device....but why would I want another of the same fuse on the line....to protect the wiring itself? My block doesn't have fused outputs...just connections.

Exactly. If you have too much current going through the wire as a result of a short, you want to protect that wire so it doesn't heat up and possibly cause a fire (if it's under carpet or something).

I think 100 amp breaker will be much overkill at present, with the computer the only thing running...and I don't think I'll ever get enough in the car to use that kind of power. A friend and I worked it out last night, and we decided that with the PS, and a 300 watt amp (or around there) I could use a 40 amp fuse and still be safe. My car is a 2 seater, very small....I can't add much more. That 40 is with the other devices fused as well.

You want a fuse to break if there is more current going through the line than the equipment can handle.
There's no answer for what size fuse you need. It depends on the equipment you're running, which varies from individual to individual. It's nto too difficult to calculate, though.

**Mrcat88** · 06-25-2006, 11:41 AM

Darque thanks for the reply...

So i think I am OK. I'm thinking a 20 between DB and Batt will be fine with just the carputer running. I'll step up to a larger fuse when I add more, and fuse the caputer line with another 15.

Thanks for the help guys!

**v8 scimitar** · 06-25-2006, 02:13 PM

I always allow about 25% more than whatever your running needs fuse wise and cable wise. So although the M2 has a max of 15A I would run a cable to it that will handle atleast 20-25A and fuse the supply end of that for 20A. If you run a 100A cable from battery to DB then there is no problem with putting a 100A fuse at the battery even if you dont need that kind of power remembering that you have 20A fuse later on to protect the smaller cable to your PC.
As far as wire size goes all I was meaning is that I know the states still uses gauge as wire size but I have no idea what 8g is in the european mm although I could guess that its around 3mm.......I think, maybe lol
Circuit breakers react much quicker than fuses and with less of a fault load so they are beter to use than a normal fuse. So long as your breaker is meant for a car and you plan on adding more stuff to the DB later on then I would use it now. Why do something now that you think your going to have to change later and have to do it all again.

**parksgm** · 06-25-2006, 03:21 PM

Originally Posted by Mrcat88

I just didn't want to overpower the M2 or fry it.

This is a common misconception. Electrical devices only draw as much current as they need to operate, and no more...hooking a component up with a larger size wire than necessary will not allow "too much" current to flow to the device. The only harm it could cause is to your pocketbook...larger wire is more expensive, and if unnecessary, a waste of money.

Converesely, a wire that is too small will heat if excess current flows through it, potentially melting the insulation and leading to a short that could cause a fire.

Sometimes it helps to use an analogy. Consider a water pipe with a garden sprinkler connected to the end. Voltage can be thought of as equivalent to the water pressure within the pipe, while current can be thought of as the volume of water that passes a given point in a second (the "flow"). A sprinker hooked to the end of the water pipe will only let a certain flow of water through it at a given pressure, regardless of the size of the pipe that you hook up to it. Similarly, your power supply will only let a certain amount of current (flow) through it at a given voltage (pressure).

**Mrcat88** · 06-25-2006, 03:32 PM

V8 - Thanks, good thnking. 8g is about 4-5 mm, closer to 4, I think. I have 8g powering a 300 watt amp in another car, so this should be fine. It's plenty capable of taking a 20-25 amp fuse.

My thinking with the breaker was that I would only need around a 50 amp protection, so I did not want to put a breaker on that will not trip if there IS a short. I was thinking of using it anyways...but I don't want to create a situation where the breaker did not trip, even though there was a short, and I have a huge carfire on my hands....that would not be good

Both power and ground will be 8g, switched only 16 or 14g, not sure which, but plenty for switched.

Of course, I would also like to run a power inverter to power a PS2 somewhere down the road, so maybe going with the 100amp breaker now would be the right thing to do. I don't think I would have to worry about it after that. Besides, I bought the breaker and have never used it....it needs to get used.