Dual Battery Wiring

[odie602r]

The tubs on these cars are not grounded well
U have to run a ground wire from the tub too the chassis rails

If its all being connected to the factory point is this still required?

[big_bob_thefirst]

Ya, wiring would b right.

And to hvac point, the actual flow is actually from the - terminal to the + but the current goes from + to -...

That's y u need the fuses on the positive... That "physics" bit is a bit messed up.

[big_bob_thefirst]

The tubs on these cars are not grounded well
U have to run a ground wire from the tub too the chassis rails

If its all being connected to the factory point is this still required?

If u run a cable, no its not required. The tub just won't b that good of an earth. If u run cables everywhere, it's not an issue.

[ag9111]

Point of order here guys as everybody is using different terminology and most of it is wrong, which is confusing people.
The negative post on a battery in a car is neither ground or earth, it is a floating system. Those are terms related to systems where there is an earth rod driven into the physical earth or ground and the neutral is referenced to earth.
The negative post is negative or 0V, the positive post is positive or 12V. In a vehicle the chassis is at 0V or negative potential and is refered to as chassis or ground plain, not just ground. In all schematics it is drawn as ground plain.

So to answer your question odie602r
1 Negative post to Negative post is best, in the same size wire as the positive, but I bolted mine at the chassis end of the main ground plain wire coming off the negative post, for neatness and ease of removal of the battery. It is so close that it doesnt matter. Naffs issue was that he connected his Aux negative to the chassis in the tub and had a bad connection form over time

2 & 3. No issues will be caused if you wire all your aux devices straight to the aux negative terminal or to a negative buss that is wired to the aux negative terminal/post.
If you wire your auxillary devices to chassis than you will need a cable from the Aux Negative post to chassis. This method I do not recommend

[odie602r]

it's getting clearer every time I read this post - thanks ag9111.

Now I understand, it's time to order the components then have some fun wiring it all up and pretending I'm an auto electrician ...!

NewTriton.net should seriously consider becoming an RTO (recognised training organisation) - I'm sure I've learnt more about car systems on here than i could have in a TAFE course!

[irwazza]

If you wire your auxillary devices to chassis than you will need a cable from the Aux Negative post to chassis. This method I do not recommend

Just interested as to why you don't recommend this? Is it the possibility of getting a bad earth over time?

[ag9111]

If you wire your auxillary devices to chassis than you will need a cable from the Aux Negative post to chassis. This method I do not recommend

Just interested as to why you don't recommend this? Is it the possibility of getting a bad earth over time?

Yes

[hvac guy]

Ya, wiring would b right.

And to hvac point, the actual flow is actually from the - terminal to the + but the current goes from + to -...

That's y u need the fuses on the positive... That "physics" bit is a bit messed up.

Nope current goes - too + as well
Fuses are put on the + terminal as faults will be to ground plain, years ago cars used to be
+ on chassis and fuses on the - post.

Benjamin Franklin was a smart man.
But I reckon Nickala Tesla was smarter he,s the reason why we have ac power
In our homes instead of dc like Tomas eddison wanted.


Anyway back on topic. Make sure every connection point is super clean.
It will pay for itself in the long run.

[big_bob_thefirst]

Here's a picture how I wired up my battery. Long wire distance between the CB's and everything else was pretty short.

[Mooons]

conventional flow V electron flow
You guys are starting to make me feel like an apprentice again

[ag9111]

Should be Ground Plane not Ground Plain

Didnt look right when I was typing

[odie602r]

Does anyone know if "8mm twin" is the same size as 6B&S?

I've had a place tell me that their 8mm twin has a higher amp rating than 6B&S (something like 82A for 6B&S and 90A for 8mm twin) but the person I've spoken with doesn't know the cross sectional area.

6B&S is 13.5mm2 or pretty close to it. Anyone know this measurement for 8mm twin?

[Mooons]

I must be on a different planet all these sizes are strange to me
4mm2 6mm2 10mm2 16mm2 these I know
I ran 25mm2 from front to back cos it was free & I know I can use my aux batt to drive my winch if I have to with no problems

[odie602r]

Free 25mm2 - that's a handy catch!

[big_bob_thefirst]

Bloody sparkies...

And no idea on about the cable sizes.... Google!

[odie602r]

All I've been doing is googling it - found plenty on B&S, AWG, SWG, cross section area, conversion from one to the other, info on 6mm twin auto cross section area but nothing on 8mm twin.....

[jetcrew]

Does anyone know if "8mm twin" is the same size as 6B&S?

I've had a place tell me that their 8mm twin has a higher amp rating than 6B&S (something like 82A for 6B&S and 90A for 8mm twin) but the person I've spoken with doesn't know the cross sectional area.

6B&S is 13.5mm2 or pretty close to it. Anyone know this measurement for 8mm twin?

Doesn,t sound quite right to me , If he was talking about 8mm then that would indicate an auto sizeing, in which case the cross sectional size is always smaller than what the name suggests. No refernce in my NARVA book to an Auto 8mm cable. It would have to be around 6.5mm2+ I would think if it is out there.

AUTO
4mm = 1.84mm2
5mm = 2.90mm2
6mm = 4.59mm2

Then you have B & S where the B & S replaces the mm in the first colum
8 B&S = 8mm2
6 B&S = 14mm2
4 B&S = 20mm2
3 B&S = 26mm2
2 B&S = 32mm2
0 B&S = 49mm2
00 B&S = 64mm2

then we have solar grade cable which like the normall sparkie stuff is just plain and simply called what it is
Solar
4mm2 = 4mm2
6mm2 = 6mm2
10mm2 = 10mm2
16mm2 = 16mm2

So I guess if you always find out what the MM2 size is, then you can always check what you are being sold. No matter the type of cable. would be much easier if we all just used MM2.

Jet

Note- sizes taken from the Narva Catoulouge other manufactures might be a few mm different like
6B&S = 13.5mm2 NOT 14mm2 , but they are all around that size.

[Thommo3337]

Just to add cables arnt rated at certain ampres factors come in to working this out like voltage drop (longer the run the more loss in a cable) the way you run it wether it is bunched in with other cables, temp etc so going the minimum cable might be suitable for a 3m run but not for a 6m run! Circuit breakers in houses have a better trip rating than a fuse! Cb can be reset fuses can't!! These batteries can put out some serious power houses these days have 63amp main switches to run everything in the house just to put it in perspective. Always protect the cable with a circuit breaker suitably rated for that circuit therefore limiting any damage caused from a fault...

[Quinny]

It's hard to explain what you are trying to say sometimes ... but here goes ...

(... and I don't want to upset Lunny again ... he's such a serious man ... )

I was looking for a recent post from someone, in the various 12 volt threads (It may have been Salty ... not sure) but basically the gist of it was, that the secondary, deep cycle battery was fried because it was being charged by the alternator alone, via a voltage sensitive relay ... Not enough voltage to correctly charge and maintain the deep cycle battery.The battery life was shortened considerably in my opinion. This has been discussed before ... and until you see it yourself ... you think WTF happened there ???

... Well ... I read Captain Snooze' tread, 5th's and a few others - this confirmed my thoughts.

This is the VSR that I'm using ...




Even after all the research and the advice I had been given at the time , I believe this same condition has happened to my aux battery. My 105 A/h is toast after less than 3 years. (This second battery is installed in a dual tray under the bonnet, so perhaps heat may have been a contributing factor as well.)

This has been the method I have been using for camping up to now, using extension cables to the tent site for the fridge & lighting ipod etc, from the back of the ute ...


I was hoping to get a little more out of a pretty hefty investment. It's also, probably the most important part of hardware in our camping setup.

From a reliability point of view, I've been thinking ... People camp differently. What we do is find a spot, set up a "permanent" camp and go out on day trips from there. Rather than packing the fridge back in the car for every trip out for the day, I'm now looking at different options.

Even in peak condition, the 105 A/H would last for 3 - 4 days before requiring a drive up the beach for a few hours to get it going correctly again ... We really want to leave the fridge at camp for maybe up to a week or so.

I'm am thinking of having a dedicated crank battery - that's all it does ... along with the other associated electrics for the normal operation of the vehicle. That's the battery that everyone has - and that is charged by the alternator as normal .

I will retain the voltage sensitive relay to charge a second heavy duty (or marine grade) battery under the bonnet. This will be charged by the alternator as well.

I believe this would be acceptable for this type of battery. (The idea is cost saving to replace a $100 - $200 for this type of battery in case of failure as opposed to the $300 - $400 for a decent deep cycle.)

I don't really have a need for a second battery while the vehicle is sitting at camp doing nothing.

Existing wiring from the old deep cycle goes to the rear seat where I carry the fridge while travelling, and into the tub to a dual ciggy style outlet. I'll leave this as is for now ...


The idea is, I will run the car's internal accessories from the second battery - like the Alpine 4x 100W amp and canopy lighting / compressor / work lights etc. (That Alpine thing will kill a battery pretty quickly... ) All the stuff that you use while stationary but don't need to remove from the car - basically low amperage drain stuff ... - It will also serve as an emergency second crank battery (via jumper leads.)

I am thinking of using this second battery under the bonnet, to be a dedicated charge battery for a third 120 ('ish) A/H battery via a cteck 250S Dual .

I have some 16mm sq cable that I will run from the second battery to the the tub in some 20mm split sheathing and terminate on a bus bar arrangement similar to what Naff posted earlier in both the engine bay and the tub with appropriate fuses & circuit breakers... and an Anderson style plug in the tub.





I'm going to put a deep cycle in the ARK box and the 250S will be attached to the top of the box, and will have a Anderson plug to connect as mentioned above. This will also allow me to not only remove the deep cycle battery from the car but also connect a solar panel while on site ...




My question is... I read on here that some people are running 25mm2 to the tub ... I'm going to do 16mm2.

Buggered if I can find that formula to work out voltage drop ... (all I remember is V = I x R ) - but does the ctek do the electrical trickery to up the voltage to an the acceptable level of 14.4V or whatever to look after my new deep cycle regardless of current ?

Just trying to find a more reliable solution ...


Thanks,

Q

[hvac guy]

Sure does quinny if U want too check out mine and how it works your quite welcome.

[Quinny]

Sure does quinny if U want too check out mine and how it works your quite welcome.

You were the other bloke that knew about 12V batteries ... Sorry H-Vac ... I read your threads as well ... 16 mm sq ? is that enough to charge a battery in the tub via a ctek ?

[Cowboy Dave]

I thought the ctek was capable of running as an isolator on its own, so running it with the vsr might be doubling up on the same function?

[big_bob_thefirst]

Quinny, the ctek manual says 10mm2 for up to 6m, so 16mm2 should b fine.

And it's meant to do the different life cycle protection charging and get the 100% charge. I'm not sure if anyone has measured the highest voltage off of the ctek.

What ur saying though makes sense. Just putting the batteries in series. Not sure if the first isolator could act as some barrier on the ctek charging the third battery but it shouldn't I think.

[Snooozy]

I have a voltmeter on the dash which switches between main & aux batt.
the ctek keeps the aux battery at up to 14v with no real load on it eg no fridge.
usually sits in the high 13v range.

The aux is usually at a higher voltage than the main, so ctek does work very well at boosting the voltage.

I dont remember what gauge wire I used but it is powered from the Bus rails connected to the main batt via a breaker
as CD said above, no need to run off a VSR.


check this site under cable& wire tab for info on wire size, resistance etc http://www.12volt.com.au/

[hvac guy]

So quinny U want to have a start battery charge first then the vsr charge the second battery and the ctek charge the third battery. So the ctek won't charge unless the vsr is on And second battery is up to the cut in voltage of the ctek.
The first battery and second battery would have too be of the same type but the third could be whatever U
Want as the ctek will automatically detect type and charge is accordingly.
Chuck up a wiring diagram too show what your thinking if this is wrong.