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it depends on what kind of problems they are talking about. assuming whatever you downgrade it meets the requirements of the device, there is no issue there. the only issue i can possibly see is that cutting the cable adds a failure point-- if one of the bolts were to come loose, etc.Quote:
Originally Posted by DracoPCGuy
yes. it should always be at least as large, if not larger then the power input wire.Quote:
Originally Posted by DracoPCGuy
Thankyou for your feed back...on both there. I have done Amp installs before and did the 2 gauge to the 4 gauge after a spliter and never had an issue but for the first time I was doubting myself after a couple people said they heard that would cause issues. I don't see why it would but I thought maybe I was missing something.
I have always used atleast the same gauge ground as the power. maybe to make it easier I will take a good ground point(usually i used a bolt down spot for a seat) run a spliter off that and distribute to everything that way there is a 2 gauge being split to 4 gauges. This would make it the same as the powe then. What do you all think?
sounds good.
I'm a bit late, but...
FYI - 2G = 0.1563 Ohms/1000, hence R = 3.4mR (milli-Ohms) for 22'.
V = IR (Ohm's Law).
Hence a voltage drop of 340mV = 0.34V over 22' at 100 Amps.
That IMO is quite reasonable for 100A. (Or rather, I try for well under 0.5V drops in power circuits...)
Plus relay and fuse and connector drops...
Re going to smaller wires... (Relax and bear with me for two lines...)
Oh yes, big problems because the +ve ions hit the "reducing wall" and bounce back, hence building up in the battery until it explodes.
Meanwhile the returning electrons suffer decompression which splits them apart. Now if you've seen a hydrogen atom splitting (H-Bombs) trust me - you do NOT want to see an electron split.
Okay - the above is total bullsh.
That's right, the H-bomb is a fusion bomb - there is no splitting involved (that's the Uranium fission bomb).
But the rest is true... well it is when someone else says they read it on the net....
The 2nd & 3rd line in this block are complete bullsh, but I occasionally like doing what others so often do (but not on mp3car - yay!). I'm so tempted o say how it flattens the battery because in actual fat the returning electrons combine with the bounced +ve ions ad cancel out, hence the battery increases its output etc etc...
Why did I write this? It reflects the crap else misunderstanding I so oft read in webland. (And the occasional sanctioned legit book/reference!)
Now, re going to smaller wires...
Assuming the wires are sufficient gauge and protected, then no problems.
Protection may be physical - ie, maybe no fuse, but a short "is guaranteed" not to occur.
(EG - the 2G is fused at its battery end (with a "2G" rated fuse) but the DistBlock cables are smaller and not fused.)
Besides, in practice, a smaller gauge (4G, 8G etc) will (most likely) still blow a 2G fuse if short circuited because fuse ratings are to protect cables from excess heat (ie, current overloads) as well as the much greater short-circuit current. (Is that clear & sensical?)
Also if the small gauges are short, they may get hot but the ends may conduct that heat away sufficiently (eg, the DistBlock & other cables, and the amp/load connections) hence allowing the cable to be over-driven. (But if its insulation does melt... That's where its physical protection is important - heat-poof sleeves, or being sufficient distance from other conductors even when hot and expanded.)
Big to small is often used simply to reduce the voltage drop - ie, reduce the resistance.
EG, 5G may be sufficient for the load. But 5G has double the resistance of 2G (0.31 vs 0.16 Ohms/1000'), hence using 2G for (most of) the run halves the cable voltage drop.
The 2G cables fuse (battery end) should be to protect the 5G cabling at the far end (eg, ~120A instead of ~180A), but if the 5G is short etc as I described earlier, it could be higher.
Sure, the smaller cable section may have increased resistance (per length), but it's only a relatively small resistance at the end - it shouldn't add much to the overall path resistance.
And although conductor changes can effect high-frequency AC circuits (wave theory), this is DC. (Though noise is AC, but we eliminate that don't we? Unless it's not a problem, ergo, we are talking about DC.)
Not that I recommend nor endorse running cables above their rating, I am merely mentioning practical options and considerations.
Done incorrectly, loss of vehicle and life could result...
Attachment 66204
(The "Car Toaster" pic courtesy of 2k1Toaster. Brilliant man, and IMO a brilliant pic.)
Okay, that pic is about using cig-sockets, but the idea is the same - heat causes fires or explosions etc.
I hope I've provided some demystification. It's just a pity about the resulting confusion (LOL).
And no matter what the situation, remember to occasionally check or feel for heat - whether wires, connectors etc - BUT beware fuses - they are often normally quite warm to hot!!
And that goes for ANY wiring etc.
Connectors age and build up resistance, hence heat, and may eventually melt or flame.
And loads can be added to cables, or cables may degrade (especially at joins).
PS - the resistances I used for the 2G & 5G (from powerstream's Wire Gauge and Current Limits may be at room temp as opposed to engine-bay temps. (Resistance increases with increasing temperature.) Not that many seem to worry about that... (Possibly reflecting the extra margins used when rating quality cables.)
I haven't read the entire last post yet because I am running out the door as We speak...but I can say all the lines will be fused also...so any branches from the splitter box will also be fused before going nto the device taht it is powering. I guess my confusion then is this...if you can't safly step down gauge(the basic jist that the above post is telling me right now) then how can you hook computer power supply into any line? every power supply install I have seen look like it has a 16 gauge wire powering it from the 4 gauge wire fro the battery. Like i said I never had any problems stepping down an amp..but want to ask you guys before I assume on a PC its all good.
Read it again.
You have interpreted the exact opposite of what I was trying to convey. (That might be my fault - I'll reread MY post later - but I hopefully it's your rush...)
It is safe to "step down" as I described above.
Otherwise, what was it that the "couple people said they heard that would cause issues"?
Maybe they heard someone reading one of my posts and they simply did not get the joke...
Or is it another "someone heard" but without any detail?
Bad info is worse than none. A little knowledge is a dangerous thing. Webland has every possible answer to any given question - take your pick. Etc etc...
I'll consider but otherwise ignore vague and unsubstantiated claims - I have certainly disproved many.
OK back from work...Had a chance to read your full text and a chance to ask the couple people I was talking about that I kow but unfortunatly cannot get ahold of those I don't know as they were just people employeed in an autoparts store that are no longer employed there (that might be part of the answer). The person I know claims to have heard it from a Radio Chack employee. That explains that there. If I hadknown that in the first place I told ther person I would have told him never mind wat your saying is garbage. Radio Shack...You've got questions we have blank stares.
So for that I am sorry for wasting the typed words. As for skiming your post...I think mostly it was your mixture of fake facts mixe with real and I must have missed what your were getting to in my hurry to read. Darn my 2nd grade reading level :)
So that aside what do you think of my power install choices?
Ha - all is cool. So that was the autoshop I was in a while ago when dictating my "joke" to my Dragon?
At least they were honest - they said they heard. Unfortunately many in the industry do that, with little understanding. Sometimes the real talented people that may also work with them may get a chance to straighten things out.
As for your quick skim, totally understood & agreed (geez, I do that way too much!!).
Normally I'd like to bold before and after a jest start & /jest end, but that spoils the humor. But maybe I should do that - written media is not like a captive live audience where any suck-in can be gauged and then explained. (It's a good way of sorting those that think or know from those that don't, and those diplomats & thinkers that are still assessing the "data".)
Once upon a time, employees tended to learn and understand. But these days with non-permanent or secure employment...
As to what I think, may I simply quote Soundman... "sounds good" ...?
Without going into the detail, it sounds good to me, especially if each sub-feed has its own fuse.
It's only if trying to minimise fuses that my extra info may be useful. IE - no or less sub-feed fuses due to short or physical protection - assuming the loads have their own protection fuses.
Yeah for right not the 2 gauge feed will be split probably just 3-4 4 gauge...depening on which printer I get. The 1 will be a small Sony 4 channel amp witha fuse. Anotehr would be the computer. Now I am wondering how to do the monitor in all this. I wonder if it would be ok to put that in the mix with all this...maybe on one of thoe 4 ports. Then finally the last one would be saved for another amp when I get the subs. Everything wouldbget their own fuses...wouldnt even think of doing this any other way.
Or do you think maybe I should consider running the second amp on its own line when it happens?
I figured I'd always want a separate feed to a BIG amp so that burps don't effect the PC etc.
And also so PC etc noise doesn't effect the amp.
But it's a case of whether there are issues (noise) and if the amp(s) are big etc.
2G is a pretty big run for "normal" stuff.
If the amp is okay on that "common" 2G, then fine.
If not, maybe a smaller run later for the PC - or a larger run for the amp - depending on what the problems are.
Mind you, big amps usually use a 2nd battery mainly to take the "burp" strain off the cable from the alt/main-battery, ie - to reduce voltage dips. [Forget caps EXCEPT for multi-kW systems with AGM batteries where caps can preserve AGM life.]
But also for battery independence... A battery isolator (UIBI, smart, etc) disconnects the aux battery(s) from the main when NOT charging, hence ensuring sufficient cranking power in case the amp is left on too long etc.
Aux batts can also be used for PCs etc for the same reason (don't flatten the main battery) or for "cranking ride-thru" where the main batt's voltage dip would cause outage or shutdown.
The aux battery philosophy can lead to 3 batteries - the main, the smaller for the PC, and big for audio (or several big for big amps) which seems excessive, but that may be warrented/required in certain cases.
The blessing is that only one "auto isolator" is required. IE, a master isolator - whether smart, voltage sensing, or the ultra-cheap and reliable DIY Ultimate Intelligence Battery Isolator (UIBI) - merely energises the isolating relays for each battery.
Hence only a small "master" battery-isolator capacity is required since it merely energises other relays.
The other isolating relays are sized according to requirements - eg, a st'd 30A for PCs of a few Amps to 30A; 250A for a 2kW amp, etc.
Also "extra" GND pathing is a common suggestion. Mainly because a blown GND can be disastrous (major equipment destruction), but also because is it often cheaper than "extra" +12V feeds.
IE - if using the chassis a a GND, the GND cables are shorter than the hot (+12V) feeds.
And since redundancy is implicit, may parallel grounds can be used at different locations - ie, losing one has no impact. (Rather than using/buying a heavier GND gauge, double or triple up on the gauge used for the +12V.)
And if using a dedicated GND cable back to the battery, why not add the chassis path as its parallel GND path?
[ There can be reasons against the above like GND loops or where chassis GND could cause problems if other BIGGER loads (winches etc) use your audio cable GND as a GND path, but since amp chassis are usually GND and bolted to a grounded chassis that usually happens anyway. ]
It's often a suck&see approach.
But others hereon with real experience can advise better than I.
I'm just happy when people install a good foundation from which to work or expand. And it sounds like you are sizing adequately (or maybe overkill) and that's with the future in mind, else a "minimal power loss" philosophy. (But I still haven't reviewed you currents etc n detail... Though I did provide that ~1/3rd of a Volt drop per 100-Amps for 22' of 2G so you can get an idea.
[ Considering some text books consider a 3V drop the max acceptable for general vehicle wiring, my 0.5V target seems overkill. And it can be for BIG loads (cost and size considered). And for loads with SMPS (dc-dc converters, big amps etc), the voltage drop shouldn't mater much - noting that I know big amps seem to behave more like resistors than SMPS for reasons I don't yet understand. (My Kicker sample is still on my lounge table awaiting my investigation....). ]
I like "safe" designs and overkill wrt to capability.
But overkill when it involves non-practicality and much expense is undesirable.
