What have you done to your car today?

[funkytown]

you add resistance though the longer the cable hence going larger than factory when you put it in the boot.

its so weeny in factory coz it lives so close to the alt and starter.

[Guest]

 funkytown said:

you add resistance though the longer the cable hence going larger than factory when you put it in the boot.

its so weeny in factory coz it lives so close to the alt and starter.

You dont geddit rhys is an A/E apprentice/maestro/whatever he does actually know.

[Roo]

 funkytown said:

you add resistance though the longer the cable hence going larger than factory when you put it in the boot.

its so weeny in factory coz it lives so close to the alt and starter.

I know

[Roo]

Cable cost me just over $40

[funkytown]

 evowrx']

[quote name='funkytown said:

you add resistance though the longer the cable hence going larger than factory when you put it in the boot.

its so weeny in factory coz it lives so close to the alt and starter.

/quote]

You dont geddit rhys is an A/E apprentice/maestro/whatever he does actually know.

i do know. and I\'ve also tested / tried it / use it like that personally so have some good understanding on the subject.

run a thin cable and feel how toasty it wil get boot mounted

[rex-leggy]

nothing to do with resistance . currant carrying capacity over distance

[loner]

How much current do you need? 50mm does seem very big...

http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html

[funkytown]

 loner']

How much current do you need? 50mm does seem very big...

http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html

dunno what a starter consumes but a battery will throw out well over 300 cranking amps

[quote name='rex-leggy said:

nothing to do with resistance . currant carrying capacity over distance

once you can spell what you\'re talking about you can enter the argument :-*

if you\'re worried about voltage drop over distance.. whats will help limit that i wonder.... considering a thicker wire has lower resistance.

[Timmah]

Another damn stone stuck between the rotor and stone guard. This time on the way to work.. Going to be a lovely drive home today.

[94 Leone]

The banter on here is worse than a cricket game or halo

Also, Overkill is always better than an undershoot, especially when it comes to electrics.

[newsuba]

 loner said:

How much current do you need? 50mm does seem very big...

http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html

50mm is huge !

maybe a decimal point got lost in translation...

;D

[loner]

 newsuba']

[quote name='loner said:

How much current do you need? 50mm does seem very big...

url]http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html[/url]

50mm is huge !

maybe a decimal point got lost in translation...

;D

If he means mm squared then the diameter is 8mm... which is good for 70 amps over 15 meters... if the starter needs a lot more than 70 amps, then 8mm sounds reasonable.

[boon]

 newsuba']

[quote name='loner said:

How much current do you need? 50mm does seem very big...

url]http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html[/url]

50mm is huge !

maybe a decimal point got lost in translation...

;D

I usually factor 250A per 50mm run when doing big, dumb s*** with 12V electrics.

A starter will typically pull about 200A. Ideally you want 50mm (0ga) but 35mm (2ga) is fine as you\'re unlikely to crank for more than about 5 seconds.

As for voltage drop, the resistance of a properly terminated (hydro crimped copper lugs) 50mm cable is measured in ohms per kilometre - about 0.322 of them - so 250A over 5m will give you a drop of 0.403v - which is actually not ideal, as you\'re losing approximately 100w of energy in heat throughout the length of the cable.

Just to put the fear of god in you, if you get a short 1 metre into the cable, and you\'re running a 0.5 metre long ground wire with a 700CCA battery,

the cable will be attempting to dissipate almost 9kw of heat and you will have a burning car real fast if you don\'t have a fuse.

Either that or your new impromptu 700A/12V arc welder will rapidly punch a hole in whatever it\'s touching.

[ADIKT]

plates arrived

[rex-leggy]

 rex-leggy said:

nothing to do with resistance . currant carrying capacity over distance

once you can spell what you\'re talking about you can enter the argument :-*

if you\'re worried about voltage drop over distance.. whats will help limit that i wonder.... considering a thicker wire has lower resistance.

you grab a 5 meter piece of say 2.5mm2 cabel and compare the resistance to the same legnth of say 50mm2 and tell me the difference . itll be stuff all.

you make it bigger for the currant not resistance

edit .... quote fail cbf fixing

[Roo]

I doubt the starter would even draw 200A maybe 180 on a cold start and around 100A warm start. The subaru starters are very efficient and the motors are relatively low compression.

My motor is a beautiful starter so I barely hit the key hot/cold as well. It\'s all taken into account before selecting cable size

[funkytown]

go look up Ohms law... (josh)

[Roo]

The resistance will increase as more current begins to flow. Resistance and heat are relative. The current through a cable if it\'s too small will heat it up and as it heats up the resistance increases meaning less current flow allowed.

Also be careful you don\'t confuse momentary current with constant current as there is a big difference in the heat produced and the cable size needed. Don\'t go by figures you googled unless it tells you whether they are momentary or constant figures

/Lesson

[funkytown]

boom. exactly.

[B4_685]

 boon']

[quote name='loner said:

How much current do you need? 50mm does seem very big...

url]http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html[/url]

50mm is huge !

maybe a decimal point got lost in translation...

;D

I usually factor 250A per 50mm run when doing big, dumb s*** with 12V electrics.

A starter will typically pull about 200A. Ideally you want 50mm (0ga) but 35mm (2ga) is fine as you\'re unlikely to crank for more than about 5 seconds.

As for voltage drop, the resistance of a properly terminated (hydro crimped copper lugs) 50mm cable is measured in ohms per kilometre - about 0.322 of them - so 250A over 5m will give you a drop of 0.403v - which is actually not ideal, as you\'re losing approximately 100w of energy in heat throughout the length of the cable.

Just to put the fear of god in you, if you get a short 1 metre into the cable, and you\'re running a 0.5 metre long ground wire with a 700CCA battery,

the cable will be attempting to dissipate almost 9kw of heat and you will have a burning car real fast if you don\'t have a fuse.

Either that or your new impromptu 700A/12V arc welder will rapidly punch a hole in whatever it\'s touching.

Is a cable an Ohmic conductor? Lol

Hehehe was just gonna throw my 2 cents in but you hit it on the head. Always funny when different levels of electrical knowledge clash....

[boon]

 rex-leggy']

nothing to do with resistance . currant carrying capacity over distance

once you can spell what you\'re talking about you can enter the argument :-*

if you\'re worried about voltage drop over distance.. whats will help limit that i wonder.... considering a thicker wire has lower resistance.

you grab a 5 meter piece of say 2.5mm2 cabel and compare the resistance to the same legnth of say 50mm2 and tell me the difference . itll be stuff all.

you make it bigger for the currant not resistance

edit .... quote fail cbf fixing

If you check the resistance with a really badass meter, like an Agilent 34420A, you\'ll see that the 2.5mm^2 cable has about 20 times the resistance - not surprising as it has 1/20th the conductor cross-section.

[quote name='B4_685 said:

Is a cable an Ohmic conductor? Lol

Loosely ohmic, obviously as current increases beyond a certain point the heat and resistance of the cable will go up... to the point that it behaves like a lightbulb. But by then your battery, and car, would probably be looking pretty sad...

[rex-leggy]

gta look like an ass sometimes ill own it

we deal with cables to carry current ... dont factor resistance because such cabel will carry blah balh over blah blah distance

[GC82GO]

 94 Leone said:

The banter on here is worse than a cricket game or halo

Also, Overkill is always better than an undershoot, especially when it comes to electrics.

Lol you must like Rugby and Mitsi Evo\'s

[Kiwi_Fozze]

Extra earthing / cleaning the earths did wonders for my car. Cold start, it turns over once, maybe twice and fires.

With cable size, yeah for starters, battery in boot setup i\'d run 1 or 0ga cables due to the amount of current drawn. Audio capacitor (2farad or bigger) makes a HUGE difference in cranking too.

Cables also increase in resistance as they heat up, yeah the resistance may be tiny, but it all adds up, especially if you have dirty earths!!!

[Roo]

I\'m once again rolling hot in the streets

hide yo wife

Wof recheck success and green sticker lifted. Bit of rego and a funny look from the office lady when I wanted 3 rego holders but only if they looked cool. And it\'s back