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New battery cable help/advice
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Author:  willy [ Thu Jul 16, 2009 10:10 am ]
Post subject:  New battery cable help/advice
Subframe is ready to go in!
But before I do that, I am thinking of running the power cable (so I can utilise the clip behind the subframe/firewall).

What gauge wire do I use? Is 8G enough or do I go wih the heavier duty 4G?


4GA OFC Super High Current Power Cable

- Conductor Material: OFC
- Insulation Material: PVC
- Stranding: 7 x 7 x 34/0.127mm
- Wire Diameter: 7.7mm
- Total Diameter: 10mm
- Current Capacity: 110A
- Resistance @ 20°C: 0.00097/M
- Conductivity: 98% up



VS



8GA OFC High Current Power Cable

- Conductor Material: OFC
- Insulation Material: PVC
- Stranding: 7 x 95/0.12mm
- Wire Diameter: 4.05mm
- Total Diameter: 6.5mm
- Current Capacity: 56A
- Resistance @ 20°C: 0.00252ohms/M
- Conductivity: 98%


Or am I on the wrong track all together?

Any help appreciated.
Author:  Harley [ Thu Jul 16, 2009 10:13 am ]
Post subject: 
4 gauge or bigger is what you want.
Every time the wire goes through something or is held by a clip, put additional plastic based tube around it locally. New rubber gasket in the boot is a must too.
Author:  Mick [ Thu Jul 16, 2009 5:56 pm ]
Post subject: 
4G should be the go.

Mini starters are rated at 0.8KW which is (at 12 volts nominal) 66 Amperes at full load. 8G cable is not rated for 66 amps continuously, it could probably handle it periodically...but I wouldn't all the same.

At full load, the 4g wire will lose 0.18 volts along it's length while the the 8G would lose 0.51 Volts. Doesn't sound like much, but it will lose about 19% of the available starting torque because of this small voltage drop.
Author:  willy [ Thu Jul 16, 2009 6:21 pm ]
Post subject: 
Excellent.. Yeah I thought the 8G would be a big light.
Some places recommend 2G, but at the end of the day, I won't be holding the starter down for any more than the bare minimum - any more and you start heating wires up; the current loss becomes higher and its pointless - if its not starting, there's something wrong!

*off to the shop later to get some 4G*

:D

PS Should i route it before the front subframe goes in or does it not really matter?? Should be able to poke it through the gap shouldn't I?
Author:  Mick [ Thu Jul 16, 2009 6:43 pm ]
Post subject: 
It is best to route it before the subframe goes in as it is a pretty tight bend through the top of the rear subframeand it goes through a pretty narrow space.

Take a look at a larger size, it will only improve the voltage drop across the cable. Look at it side by side and compare the outer diameters. If its not much bigger overall then it might be worth the hassle.
Author:  willy [ Fri Jul 17, 2009 12:54 pm ]
Post subject: 
Image

B&S is the new measurement for cable - "gauge" is no longer the industry standard.. apparently!

I have been recommended to run 2B&S - do you think that would be the go?
Author:  AEG163job [ Fri Jul 17, 2009 1:25 pm ]
Post subject: 
I think this is one of those situations where size does count. However, the quality of your terminals (& attachment thereof) is also important if you want to reap the benefit of all that low cable resistance.

AWG now defunct? Bugger, another thing to remember :twisted:
Author:  poeee [ Fri Jul 17, 2009 1:45 pm ]
Post subject: 
Do you use the 4g with the fine copper strands like I do in car audio? Standard cable for the car has thick strands. I've always wondered and never asked.
Author:  Mick [ Fri Jul 17, 2009 2:52 pm ]
Post subject: 
poeee wrote:
Do you use the 4g with the fine copper strands like I do in car audio? Standard cable for the car has thick strands. I've always wondered and never asked.

Its cheaper to make it with thick strands, thin stranded wires are typically made for flexibility as the wire is annealed to be repeatedly bent and shaken by vibrations in a car. You can pick it out as they usually specify the number of strands and the area for each in the specifications. The higher the number of strands for a given cable cross sectional area, the more flexible it will be (and more expensive). That's why supercrap cable is so shitty.




Go with what they say, they're the experts willy. As long as it's similar or larger in size to what you have now (actual copper that is) then you will be fine. Like AEG163job says, mind your terminals, and it will work just fine.
Author:  Tombo [ Fri Jul 17, 2009 4:15 pm ]
Post subject: 
I used 4G red amp power cable in my clubby, it looks good and delivers the power.

I have measured the current draw when starting a mini and it was about 80 - 90 a using an inductive pick up.

8G handling 56A won't like it.
Author:  drmini in aust [ Fri Jul 17, 2009 7:28 pm ]
Post subject: 
I use 25mm² welding cable, it's about equivalent to 3G. But more flexible, double insulated and usually cheaper to buy.
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