VacavilleFC

small changes??

new wire
new lugs cause he trashed those,
circuit breaker,
reroute the wiring mess
and grommets.

that sounds like like completely redo it to me?

and distro blocks aren't anything special if you know where to look. they use them everyday in highend car audio installations,

oh and check your brake fluid theres NONE in the reservoir
if you like your wiring to look like crap and the chance you could short everything at any time, do it exactly like he did

honestly would you do it like that? i'd laugh

uptotibet

i'm gonna do the bussman fuse thing and yeah i'll redo the lugs... i took care of the grommit...

thanks griffin


p.s. vacaville.... whats wrong with you?

scathcart

Let's walk through a gloriously over-simplified explanation:

The Mazda FSM states that the starter, under full load, should draw somewhere around 96amps. Add in the current drawn by the fuel pump and ECU to start the car, and you're looking at ~100 amps when starting.
Using some typical voltages I've witnessed: Battery, disconnected, meters out to 12.6VDC. When connected to the car, under under crank, the battery voltage drops to 11.5, but we'll say 11 at the very worst. This drop in voltage takes place due to the internal resistance of the battery: it takes some energy to force the current through the battery. Keep in mind this is measured at the battery terminals.
So: 12.6V-11V= 1.6V. 1.6V/100A= 16mOhms.
Now, let's say we get a short circuit occuring where your wire passes through the firewall. I'm going estimate you've got 15 feet of wire between your battery terminal and your battery positive, and 2 feet of wire for your ground.
So, the resistance of your battery cable is: 10.37 x 17' /(0.258")^2= 2.65mOhms.
Now we've also got the 10 feet of sheet metal between your battery grounding point and the short, but that is going to be so minute to be of any consequence.

So, we add our resistance measurements together to get around 18.65 mOhms. This is all that impedes the flow of current.

So, 12.6 V/ 18.65 mOhms= 675A.

In all reality, its going to be much more than that, since I over-estimated the resistances.

675A is enough to weld metal plate nearly 3/4" thick... Think of the amount of heat this is! Without a fuse or circuit breaker to stop the fault current, this heat will be have to be disapated across your short circuit. Likely, the battery will explode and spray acid and explosive hydrogen gas everywhere, or the battery wires will heat up to the point that they will glow like a light bulb element and set the car on fire.

Your electrician's should know this. If not, they're not much of an electrician. Speedshops rarely understand electricity, so that's not much of a surprise.

So you can understand why everyone jumped on you about the fusible link. This is serious stuff!

scathcart

Don't post if you don't know.

Battery jumper cables are typically use a synthetic rubber/PVC insulation, which helps to keep them fleixble during cold weather, although EPR, XLPE, and various other insulation types are also sometimes used. Standard automotive battery cable is also PVC insulated.
The jumper cables, due to their constant flexing, also have a thicker insulation level, and a rating of typically 300-600V. The dielectric is not going to break down under 14.5V max.
Again, due to flex issues, jumper cables also use high strand count wire, which is well-suited for high-vibration locations.
In order to be sized as #2 AWG, the manufacturer must have a circular mil area (CMA) of 66.5kcmil, so it won't be of any smaller size than rated, and sized large enough to handle the standard maximum current draw of the car.
IE: the wire is fine.

The rubber grommets used as firewall pass-through sold at most automotive stores are of a very poor choice, as they easily pop out of place and can result in chafing, and the grommets can chafe through themselves. Plastic grommets can also be used, but don't tend to grip the wire very well, leaving an air gap, nor are they fire rated. It is a very BAD idea to leave an open hole with a flammable plastic directly in the viscinty of the drivers legs and the fuel lines.
A better choice is to use a grommet that locks in place:
Summit sells a pass through designed for this, with terminals to attach lugs to on each side, and a lock ring.
A better, and cheaper alternative, is to use a strain relief connector designed for SOW or SJOW cord wire. They are available in metal or FT (fire) rated plastic at any home depot, lowes, rona, etc in the hardware store. They install with a locknut, and then use a separate nut to tighten a rubber gasket around the cable. They quite inexpensive and perfect for the job.
IE: if you recommend an improvement, actually make it an improvement.

As for the lugs: when used with the correct tool, those lugs are perfectly acceptable to be crimped. You only mentioned them because you read what Aaron posted, and wanted to dump on the guy.
IE: If you're going to hack a guy, at least have a clue as to what you're talking about.

uptotibet

hey aaron cake or griffin

the bussman fuse with manual flip... is this just a manual reset or can it also be used functionally as a manual switch to turn the positive power off (such as when i want to do something with the electrical system? i've toyed with the idea of a hella race switch but was wondering if the bussman switch could double function

thoughts guys?

uptotibet

scarthcart - thank you...
i knew the wire was fine... and i'm glad your engineering perspective corrected that

as for the pass through i toyed with the idea of a lock grommet for piping but instead i taped the wired with duct tape multiple times and then great stuffed it. its going to be fine because i wire-tied it at key locations inside the car and clamped it outside the car. if i did it again i'd probably use the summit racing pass through or whatever.

as for the lugs - i do agree i could have put di-electric grease, but the crimping was done fine---- plus the wires are air-tight from the shrink wrap i used on them. they are fine....

i def agree now on the fuse.... i'm not a moron and i do listen to people's reason... thanks for your input!

scathcart

The Bussman circuit breaker described has a push-to-trip button that will open the breaker, acting as a switch, so yes, you could use it as such. However, if you plan on drag racing, this will not suffice to meet NHRA rules for a battery disconnect.


Here is an example of the strain relief connector I was talking about:
http://www.hyperlinktech.com/web/liq...ain_relief.php

uptotibet

wow yeah those are really nice... ugh.... gotta pull the booster out again...

good to know about the bussman breaker... i wont be drag racing so thats fine for now i suppose

thanks scathcart