B+ (Alternator) to Battery cable (size)

[stradlater]

What size cable have people used to go from the B+ post on the alternator to the battery (or some point near that?)

I used one that wasn't exactly MASSIVE, but seemed to do the job on the 1g.

Now I'm finding that the wire is getting uber hot, to the point where it's blowing the 70Amp fuse it goes through.

Now firstly, I figure that the 70Amp fuse isn't enough, given that it's a 110amp alternator and the standard fusible link is 150amp. So that part I can fix.

But it looks like I need to replace the B+ line, given how damn hot it's getting. I know how I'll route the wire and circumvent the standard (1976) battery charging system, but the wire thickness I think is an issue.

I bought some 8 guage car audio wire and put that in place temporarily, seems to do the job - gets a tiny bit hot but not too much. Figure that's not 'sturdy' enough for a battery charging system, though the only reason I can think for that being hte case is the fact that the sheath is not thick enough.

Thoughts?

[George]

Maybe add some plastic case (like the one usually wrapped around stock toyota harness) and ensure the cable will not break at connection points due to vibration. Maybe add heatshrink or something at terminals to smooth transition from hard metal terminal to flexible cable. Then it's ok to use it.

p/s to give you some rule of thumb, if you can measure as much as 1V at cable ends under full load then consider it thin for your application.

[dumbass]

100 amp wire minimum
i think its 8b&s


or get 6b&s which is like 150 amp

[stradlater]

George - That 1V drop idea is genius!!! Hadn't thought of it myself. I love it!

Dumbass - 8b&s means 8 awg?

[George]

p/s well I thought again and found 1V rating too dangerous. You will actually want something closer to 0.1V but you got the idea though :-)

With 1V drop there's P=UI=1V*150A=150 Wt dissipated in the cable :-)

Sorry for misleading you

[stradlater]

Ah yes. Hehe. good point!

Either way, I'll check it. I love the idea!

[dumbass]

sometimes .1v is hard to test on a multimeter as u do get fluctuations thru alternator charging pulses

anyway most jap cars have alternators around 65 or 75 amps output so u need higher than that
so i run 100amp wire which is 8mm round
on the holdens their alternators are 120 to 140 amps so i use the thicker wire 10mm round

awg is usa specs
18awg is thin like 2mm round
12awg is like 5mm round
8awg is maybe 8mm round
so as awg number gets smaller the wire gets thicker

here most common is in mm square
or mm diameter
stuff i use is like this

2mm about 10 amp
3mm 15 amp
4mm 20 amp
5mm 25 amp
6mm 50 amp
8mm 100 amp
10mm 125 or so amp

10mm is also 4b&s
35mm is 2b&2

as u can see its fking confusing
so best thing until u get used to it is go bymax amp usage

if u only want a short bit goto local auto elect and ask for 100 amp wire
if u goto local auto parts shop they have small rolls and most always have amperage on it
but usually dont have 100amp
i buy it in 100m rolls lasts for ages

the 100 amp wire is usually just thin enough to push the yellow plastic covered crimp terminals over the copper end
any thicker wire wont fit in then make sure u solder the wire to the terminal
this wire is wire that charges battery so as long as u r getting over 13 to 13.5 volts at battery dont worry bout voltage drop
voltage drop is only an issue on main battery to starter cable and battery to fusebox/key wire
but even then if its over 13v then yr fine
voltage drop is only an issue when u get close to 12v
thats y u use bigger than u need then u dont even have to worry bout all the equations to figure out voltage drop over 50meters
or some crap

[thechuckster]

suggestion? pinch the starter Ve+ supply cable from a small 4cyl that has foolishly put the starter a long way away from the battery? Otherwise cannibalise the alt B+ cable from a large car that has alt and battery on opposing sides of the engine bay - if it's 80's onwards, it'll be rated for an >80amp alternator.

[stradlater]

Dumbass - your name doesn't describe you accurately! Thanks for the info mate, that's pretty useful. I'm actually getting 13.8 @ the alternator and 12.7 at the battery, so I think I've hit the nail on the head. Massive releif. Thanks!!

Chuck - Great idea mate - I will give it a crack next week. Thanks!

[litldv8]

eb to el falcons have realllllly long b+ to starter cable that is not all that big is you are looking around a wrecker
bright red too

Dum bass - your name doesn't describe you accurately!

maybe he likes fishing

neil

[dumbass]

while yr idling with not much on the alternator isnt getting pushed
the easiest way to know if the wire is to thin is if it gets warm or hot
and not from engine bay heat but from to much load
at ilde u wont overload it
turn fans and lights on and heater etc etc then u might push alternator up to 40 to 50 amps and wire might get warm
or the 12.7v might drop more
always test alternator with abit of load and maybe revs up over 2000 engine rpm
so measuring 12.7v at battery at idle doesnt mean wire is to thin it means u have bad connection somewhere
unless the wire is 4 or 5 metres long
is battery in boot
can u temporarily run an extra wire from alt to battery just to see if it increases from 12.7 to 13.8

[dumbass]

battery to starter and alternator and fusebox power wires are most important in whole car
always use new when replacing
look at the wiring on the good old vn vr vs commodores near the battery
the red insulation cracks bigtime and i would never reuse
also very common on jap wiring as it gets 10 or more years old is the copper gets a black coating
and makes it hard to solder not sure y i think maybe gets worse if u dont use wire for awhile
so if u pass current thru wire it wont go black but if wire stills unpowered for many years it goes black
or maybe its other way round im not sure but very common on jap wiring

[litldv8]

i will totally agree with the old wire problem
new wire is cheep really in the scheme of things
neil