Dual Battery Wiring

[dougie123]

I never thought of the potential difference in the positive, guess you learn something new every day. I use DC DC charger and thought that would handled that situation. I'll do some measuring on my set up.
I have done some VSR set ups, guess I best check how they are ageing. I have fixed up some that others installed in the past that were set up with Chassis earth, I just put it down to poor prep work to start with.

But does make sense.

[AnOldFart]

The problem is not the common chassis ground system that vehicles use but the fact that you are adding a second voltage source to that system.
If the two batteries were at exactly the same potential then you wouldn't have a problem.
Its the fact that you have two batteries at different potentials that causes the problem. Circulating currents are developed that continuously corrode the lesser terminals and you end up with black cable rot on the negative leads.
The more you isolate the 2 systems the better off you are hence all my secondary battery negatives go to there own bus bar that is not attached, mechanically or electrically,to the vehicle chassis. I have a negative cable that then runs to the secondary battery. The negative battery cable is then run to the front of the car and attached to the negative battery lead. This is the easiest & closest spot I can get to the battery so that we have equalisation of the negatives. This is more to do with maximum charging of the secondary battery. With only one point of contact of the two negatives then no currents can flow through the chassis that cause corrosion.

I am x2 with your thoughts on the need for total secondary battery -Ve isolation from the vehicle chassis to prevent circulating currents "ag9111".
That's the reason why the 50V DC Power reticulation in Telstra's exchanges is always provided via dual polarity solid copper bussbar systems and very heavy duty dual polarity power cabling runs to the individual equipment racks.
To prevent any chance of circulating currents occuring there is only ever one common building Earth bonding point used and all of the DC battery power feed distribution within the buildings are solidly electrically tied back to just that one Earth point.
Whilst "dougie123" common chassis earth method will indeed certainly work, it won't provide continuous -corrosion free- operation with the passage of time. ....

[ag9111]

One connection point to the earth bond in a telephone exchange is more to do with stopping electrical noise being induced into analogue telephone signal, as used to exist in all telephone exchanges. Same as we do today for analogue signals in industrial situations. When I design an electrical distribution board it always has a separate instrument ground with only one connection to the power earth bar, hence no circulating electrical currents inducing noise into my clean 4-20mA signals.
Different results for the same principal.

[GLRkenny]

I personally am a big believer in always trying to earth back to the battery, reason being that if the earth to the battery is insufficient it can create a charge through the cooling system aswell causing major cooling issues, I see it a lot when big stereo systems are fitted to cars, massive power cable to amp and barely any earth creating stray current charge in the radiator

[har05l]

Mines earthed to the chassis. I fitted it over 4 years ago. To date never had a problem.

Just sayin

[GLRkenny]

That's fine har05l your car, your risk.
As I said I believe in doing it to the battery, especially when so much aluminium is used in cooling systems these days

[coughy]

i know this is a old thread but can any one tell me were to get 8b&s cable joiners??
as im running the cable down the back of the car but i wont to have like a juntion box so to speek so i can run a
50 amp andrson plg
a merrit pug
a cig plg and a nother 50 amp to the back of the car near the trailer plug

so im looking for something like this

http://www.ebay.com.au/itm/271902238812 ... EBIDX%3AIT
dont wont this type
http://www.ebay.com.au/itm/CABLE-JOINER ... 19debfe719

i wont the bolt on type if there is a thing
that can handle the 8bs cable into it and then i can add little cableing to it
i need a earth and pos device pls
cheers coughy

[irwazza]

http://www.sidewinder.com.au/page107.html

They will have everything you need

[SEJ GLX-R]

I used one of THESE in my Triton and camper trailer, not sure if this is what you're after.

[biggibbo]

I have used the connector block halfway down this page

http://www.sidewinder.com.au/page27.html

[coughy]

cheers gibbo how does the cable connect to the connector??
is it just bear cable being squished in the screw down bolt???
or can u use eyelets on the end of the cable to attach???

[coughy]

ty sej that is what im after
buying one now cheers

[SEJ GLX-R]

No worries, just check the stud sizes are what you want as there are 2 versions.

[biggibbo]

cheers gibbo how does the cable connect to the connector??
is it just bear cable being squished in the screw down bolt???
or can u use eyelets on the end of the cable to attach???

Pair the cable back, and push in. Tighten Allen key screw. I soldered the end of the cable before putting it in to give a bit more strength and stop corrosion but doesn't really need it.

[coughy]

ok ty m8 will look in to this one as well

[rokster]

Hi all..

Apologies for dragging an <oldish> thread up... but. I've got a question or 2..

Assuming I go with the suggested set-up above - battery in the tub, circuit breakers everywhere, ctek charger etc etc. .does this then mean that any additional lights, accessories inside the cabin, and most importantly, the winch are being run from the main cranking battery ? Or do you run thick cables back to the front for the winch ?

Enlighten me please !

[snowman]

Hi all..

Apologies for dragging an <oldish> thread up... but. I've got a question or 2..

Assuming I go with the suggested set-up above - battery in the tub, circuit breakers everywhere, ctek charger etc etc. .does this then mean that any additional lights, accessories inside the cabin, and most importantly, the winch are being run from the main cranking battery ? Or do you run thick cables back to the front for the winch ?

Enlighten me please !

run your winch from the main battery. always keep engine running when winching if at all possible.

[azza3400]

Anyone got any photos of where they have ran there wires into the tub? I can't seem to find the spot under the guard.

[Cowboy Dave]

Better to work from the top and thread it through with someone down near the fuel filler to spot it and pull ot down. Look up under the rail maybe a foot back from the very front of the tub. Maybe a little less - been a while since I looked at mine.

[azza3400]

hard to see much with the tub liner or am I not looking in the right spot?

[Cowboy Dave]

Is it an under rail liner? If it's over rail you won't see it.

[azza3400]

yeah it is. I found a spot right up the front corner of the tub. hopefully the bigger wires fit through. cheers dave

[Pom10]

Hi. I have 2 125 ah gel batteries in the tub which are parrell with a redarch regulator/ booster behind the rear seats
My question is how can you tell if the resettable curcuit breakers actually do work ?
I have 2 resetable circuit breakers inline ( one near the main battery under the bonnet and 1 after the redarch regulator and before the 2 batteries in the tub

Cheers
Pom 10

[Pom10]

Hi mate
Not sure actually whate you mean ( please can you eloborate)

Cheers
Pom10