Ceap DIY Dual Battery Setup.

Jeff
how big (or small) is 4G and 8G cable, in mm Dia. (of actual metal cable) because to use in a Camper Trailer situation you would need minium 25mm cable to avoid voltage loss at the Aux battery.

You may think that I am a bit of a dill regarding all these different wire gauges. I was brought up in the old school and work on the old British Standard wire gauge ie Australian Standard wire gauge where the wire was measured by the cross sectional area not the diameter and where the smaller the number the thicker the cable. This is contary to the American standard. I have also noted that some cable manufacturers market their cable on the diameter of the outside insulation so be very carefull when you buy cable

Was it called Mason or Matson or something like that?
If so I fitted one to my Challenger and it seems to work fine. I've not had any heavy duty use of it yet but it was easy to fit. They give you heaps of cable (Decent size cable). I got mine from a 4x4 shop for $99 which was cheaper than the price of it in a battery shop ($129) so $95 seems a pretty good price. States on the pack its perfectly suited to charging batteries of different types (its then up to the charging system to manage to pump out a full charge).

With the Redarc solenoid the "optional manual overide" is designed to allow you to use the second battery as a start battery if your main goes flat.

DO NOT ATTEMPT THIS UNLESS YOU HAVE USED HIGH CAPACITY START CABLE!

By this I mean cable capable of carrying around 500amps. You'll fry your electrics and quite possibly start a fire.

A few points
The US AWG standard is actually based on cross sectional area - but is expressed in non-related numbers.

'Amp ratings' of cables are totally meaningless in terms of voltage drop. This rating is a fire rating only and indicates the maximum current trhe cable can carry withiout it's insulating melting. Thus a '50' amp cable may have an acceptable 0.2 volts drop over a metre or two, but as much as 10 volts drop over (say) 50 metres.
These ratings also vary hugely depending on insulation material.

The only meaningful indication is conductor cross sectional area in square millimetres - as is used in house wiring. It is the ISO standard. Thus 2.5 mm mains-voltage wiring (in Aust) has 2.5 sq mm conductors.

Auto cable (the stuff you buy from auto parts stores) is rated in terms of overall diameter - that is insulation and all! Thon ONLY information it gives is the size of a hole you could poke it through.

6mm auto cable is not too bad - it's about 4.6 sq mm. 4 mm auto cable is usually 1.8 sq mm - less than half the size most people think is. 2 mm auto cable is about 0.5 sq mm (better than wet string but only marginally). Exact comparisons are not possible as auto cable insulkation thickness varies from maker to maker.

Not realising the above is the main reason why so many 12-volt fridges (and charging circuits) dont work too well.
Collyn Rivers

GraemeD
Not mine - but there are quite a number of privately-owned OKAs around - probably about 60.

They are a truly excellent vehicles as long as they are properly maintained. One needs to be cautious when buying as many are ex-mining and ex-tour vehicles and have not been well enough looked after: hence the price range: from $30,000 for a rough one to well over $100,000 for a really good one.
Collyn Rivers

Battery Cable is sized as “mm squared” and is commonly referred to by B&S sizes.
8 B&S is 7.5 mm squared
6 B&S is 15 mm squared
3 B&S is 25 mm squared
2 B&S is 36 mm squared

Automotive wire
1.2 mm squared wire is generally rated to 10amps
2.0 mm squared wire is generally rated to 15amps

So the Redarc spec cable is between 3 B&S (15mm) and 6 B&S (25mm)

Where does the 4 or 8 guage cable fit in with the above size's ? ?

Just a quick follow up. I have used 4g OFC power cable for my set up from Altronics. It is very flexable as it has many strands in it. The only problem is that you can only get it in red & black

Jeff getting away from all the wire jargon, is this set-up an under bonnet or one of those battery boxes that fits in the back of the bus or van?

Cheers Dunc.