It should be around 14.4 when running unless you have done other 'improvements' to your electrical system. [/QUO

It should be around 14.4 when running unless you have done other 'improvements' to your electrical system.

first off not all cars charge at 14.4v it depends on the alternator in my case my alternator charges at 13.5v

 

13.5v is a pretty low charging voltage for normal lead-acid battery terminals at normal temperatures. Normally that's something you see if there is a bad connection from the alternator.

 

13.5v is a pretty low charging voltage for normal lead-acid battery terminals at normal temperatures. Normally that's something you see if there is a bad connection from the alternator.

first off not all cars charge at 14.4v it depends on the alternator in my case my alternator charges at 13.5v

 

first off not all cars charge at 14.4v it depends on the alternator in my case my alternator charges at 13.5v

I don't care what your alternator charges at. The voltage requirements for proper electrochemical redox reactions for a nominal 12 lead acid battery to be fully charged is more than 13.5 volt. It can float at that level (the float level is usually a little lower than that) at 100% SOC but a discharged battery needs more.

If you run something other than lead-acid that might be OK.

 

What does reverse polarity protection have to do with anything in the event of the the switching devices shorting out full on permanently? if this occurs current will still flow to the power clamp as if the device was never installed

For that matter, why do you think you even need it? How often do you change batteries in your vehicle or jump start it and get the battery in backwards? Why wouldnt have it. its there to protect my components

As for the gold plating guess again.
Ever look at the gold plated battery connectors on high wattage audio systems? They corrode just like everything else. Slower than plated copper but they still corrode just the same. The sulfur compounds in the battery may not directly react with the gold but it does just fine aelectrolytically dissolving pinholes in it to where it can then attack the underlying copper. it take time for sulfur to occur so stop telling me that i aware of this from day one . i dont want to make this and mass produce it i just want it myself only. BTW i have sundown audio 7500rms with actual gold plated terminals on my vehicle and no corrosion didn't occur until after the first year and it still worked

If it was me I Would be building it into its own box and attaching it remotely on a firewall or some location away from the battery like is done with any other vehicle primary electrical distribution point. There's a reason all manufactures of anything that uses large batteries try to design their systems to only have one large cable and single connector on a battery and all other components located away from the battery. i dont want that


Also Infineon has high levels of experience in analyzing the practicality of application, design and fabrication of their products. Pretty sure you don't given the questions being asked here and attitude regarding our numerous reason to doubt your design and overall point and purpose of your design. Infineon design there version with 3oz copper top and bottom layer and internal power plane two of them with 12 oz of copper thickness it handle 450amps of current when they had it on for 10mins at temp of pcb 60c no problem. And they still continue testing after that current level of 450amps.

You can build it and no one here will try and stop you. Heck I am wanting you to build it now just see what possible levels and costs of damage this thing causes when it does fail. Your not explaining adjudicate information i ask questions from my comments requarding serious questions but i get no help maybe you look at them before you respond back

Just because something can be achieved doesn't mean it can be achieved as applicably practical and reliable as imagined.

Wrong Pcb manufacturer can do these things and make them just as reliable but it come down to the design/layout in the first place my questions related to layout

 

I don't care what your alternator charges at. The voltage requirements for proper electrochemical redox reactions for a nominal 12 lead acid battery to be fully charged is more than 13.5 volt. It can float at that level (the float level is usually a little lower than that) at 100% SOC but at discharged battery needs more.

If you run something other than lead-acid that might be OK.

i am aware of this my battery (AGM) at a stand still is 12.5v and at charge level 13.5-14.2v depending on load of accessories ledbar,hid lamps, high power audio,ect my floating would sit around 13.2-13.5

 

these are the question again


1.Can i Make my Top layer the drain and bottom layer my source on the mosfet while the inner layers for power planes to assist the top layer and bottom?

2.How big can i really go on my vias for heat dissipation?

3.CAN 300amp Be Achieveable through thick 15 oz on the planes and 4-5 oz copper on top and bottom total cooper oz used on the board is 40oz so your telling me this still not enough?

 

Here more like it

 

Wrong Pcb manufacturer can do these things and make them just as reliable but it come down to the design/layout in the first place my questions related to layout

Are YOU a PCb manufacturer?

 

I'm not trying to be smart or anything but I've seen copper encased and just because it's hooked to the battery it corroded.Now hooked to a battery things to start a car things to keep you from hooking the battery wrong. You going to remove the starter wires and move to the black box.
I got a smart car it's to smart now the cables had to be recalled the computer couldn't find the engine and shut down that in turn stopped the steering the brakes and the computer flashing to put car in park plus no parking brakes. I'm at ten recalls. I'm sure that they thought they was making the car better just thank god it didn't try to park it self.

 

It's obvious none of us here (and possibly elsewhere on the planet ) have tried pushing 300A through 15oz copper sandwiched in a multi-layer pcb. I suggest you get yourself a patch of 15oz copper, sandwich it appropriately and do an experiment to see just how much current it can take without getting excessively hot.

 

Heres what I see.

To carry 300 amps in an automotive application without excessive voltage drop and heating effect you would need copper cross sectional area equivalent to that of a 1 gauge wire which is .289" diameter or 83,680 circular mils which works out to being 65,722 square mils.

http://www.allenelectric.com/referencedata/wire_size_cross_reference_chart.htm
and
http://www.kylesconverter.com/area/circular-mils-to-square-mils

15 oz copper is 20.55 mils (.02055") thick. So, 65,722/20.55 = 3.200 inches wide.
http://www.pcbuniverse.com/pcbu-tech-tips.php

Sure you could design it to use half or less that copper cross sectional area but then you have problems with the thermal aspects of resistive heating to deal with.

This is easy to find data and simple math someone even slightly familiar with electronics circuit principles should be ble find and work with which to me strongly implies that at this point in time you likely have no clue what you're doing let alone how to properly engineer anything that would safely let alone reliably work a automotive environment so references to what the high end commercial engineered products do is of very little valid comparison to what you are obviously capable of doing.

If you want to compare your design work to what Infineon corp does I would say you're at the equivalent of a low level janitor (garbage can dumper) or a groundskeepers assistant (rake/shovel holder or hose dragger) but certainly you're not up to their engineering equivalency by any rational stretch of the imagination.

So could it be done? Well yea. I and likely most everyone else that has helped in this thread probably could knock it out as a day project and have a functional semi reliable prototype to experiment with but I don't see you doing it any time soon.

 

15 oz copper is 20.55 mils (.02055") thick. So, 65,722/20.55 = 3200 inches wide.

That is 3200 mils, not inches. Oh the joys of juggling american units, gauges, circular mils, square mils and whatnot...

 

I see. I forgot my decimal place and went from there.

Yea way too many conversions to work with to derive a simple cross sectional value.

Too early in the morning too. I don't think well until noon or later.

Its been corrected.

Still getting a solid distributed contact on that thin of plating would require a heavy buss bar to be soldered to it and I am not sure how that would be accomplished with a 4 layer PCB other than a bunch of via's to reach the center two layers.

I work on larger power inverters that handle that sort of currents and they use large soldered on buss bars plus distributed wiring connection points and heavy solder overlays over all of that to carry that level of power without overheating things and still it's common to have all that literally blow right off the boards from time to time.

Getting that much current though raw circuit board traces is just not done. There's just too little point of contact conductor thickness to work with.

 

FWIW.. I routinely run 100A through a 1" trace (double sided) on 4oz copper in 65 deg C ambient without any problems/doesn't exceed PCB max op temp,etc....

 

FWIW.. I routinely run 100A through a 1" trace (double sided) on 4oz copper in 65 deg C ambient without any problems/doesn't exceed PCB max op temp,etc....

http://www.4pcb.com/trace-width-calculator.html

Seems that in ideal conditions that a .793" wide trace could carry it but that's with a ~2 watt per square inch of trace heating effect that would be exceeding standard PCB material thermal dissipation limits in any environment but fan cooled which in ideal conditions is good for up to ~ 2.4 W/ Sq In.

Give your 2 inch trace equivalent that's still around .8 watts per square inch whereas the general design acceptance is ~.42 watts per square inch standing air and ~ .8 watts fan cooled.

As noted here,

• In order to dissipate 1 watt of power a good rule of thumb is that your board with need to have an area of 15.3 cm2 or 2.4 in2 per watt dissipated for a 40°C rise in board temperature. If the board is subject to airflow this requirement can be cut in half (7.7 cm2 or 1.2 in2 per watt). These values assume that the component is thermally coupled to a copper plane that extends to the edges of the board and that the board is positioned so that air can flow freely around both sides of the board. If these power density requirements are too constrictive for your design, the inclusion of an external heat sink may be required. Also, a 40°C temperature rise is a good starting point to consider when controlling your circuit board's temperature.

From here. http://www.pcbcart.com/resources/pcb-theraml-design.html Workable but far from ideal or recommendable practice.

Going back the OP's original design given double sided 15 oz copper circuit board and the devices he has chosen he has a thermal load potential of ~25 watts @ 300 amps to deal with on a 25 Sq inch circuit board of which over 2/3's is covered with switching devices and related connector components plus would be encased in some sort of protective coating or potting putting the effective thermal transfer capability at well under ~1/4 - 1/3 of what the circuit is realistically capable of producing.

For more info, on circuit board thermal design . http://www.ti.com/lit/an/snva419c/snva419c.pdf