Dual Battery Wiring

[big_bob_thefirst]

Ya, option 2 sounds good. Don't think it'll make much of a difference in that case. I don't know enough about the red arc but putting them in series either way shouldn't impact the system.

[jetcrew]

My advice would be to mount the isolator as close to the crank battery as possible , I use 16mm2 tinned copper twin core .

crank batt - islator - cable run to rear-50a auto resett c/braker @ aux batt.

The reason I do not use a c/b from crank to isolator is that the distance is so short and all is contained under the bonnet. I do not use 1 on the output side of the isolator as i put one at the aux batt in the tub ..WHY.. because the cable may get hit /crunched/ cut , now if this happens and causes a short the short will travel up the line and the 50a breaker at the aux battery will trip. as soon as this happens the circut and isolator are switched off.

If you remove the pos cable from your aux batt and start the car you will get no voltage at the output of the isolator . It must have a battery connected in order to compleate the circut (on every unit I have installed) , with the 50A c/b at the aux battery this is 50% below the rated capacity of the isolator and 70% below the cable carraying capacity, so if i cut or shorted your cable under the chasis the 50Ac/b would pop well before the cable got hot (110A) and once this happens the isolator will switch off.thus protecting itself.

Not saying it;s the case on here but I see so many systems that have too much or to large circut protection. the role of the c/b or fuse is to protect the circut NOT the item. I see fridges with 25A fuses because people think they are being extra safe , but when the cable is rated at 15A the fuse is to big for the circut.

Now people often ask me why i would limit the system to 50A by using 50A c/breakers , the answer is that you will never see 50+amps going down the line to your aux batt, and by using 16mm2(110A) and 50A c/b the entire system has very genourous saftey margins. If you were to use a 100amp C/b then the cable would need to be 25mm2 and this gets $$$ and for not any more benifit IMHO.

circut prtection should allow 1.4x the maximum proposed current which in this case is around 35Amps of charge down the line, and if your getting 35A down the line you;d be one happy camper

And by using a twin core sheathed tinned cable it will last a long long time in all the mud grime and salt water that the underside of well used trucks see.

Hope that helps someone planning a system.

Jet

Oh and No1 on that idea about the info sheet for EMS

[hvac guy]

i have seen 50amps on my system with the old v.s.r on 10mm2 cable but now with a ctek not and issue anymore.

i prefer slow blow fuses instead of the breakers
breakers are too easy to reset
with slow blow fuses u can tell u what sort of fault u have.

[jetcrew]

i have seen 50amps on my system with the old v.s.r on 10mm2 cable but now with a ctek not and issue anymore.

i prefer slow blow fuses instead of the breakers
breakers are too easy to reset
with slow blow fuses u can tell u what sort of fault u have.

Not be rude but if you were getting 50A charge on a vsr why an earth would you take that out and limit yourself to 20A

As for fuses vs Breakers .. thats a toyota nissan debate

Jet

[hvac guy]

Agms don't like high charging currents

and U can not read a breaker

And that's 50amp peak load on first connection off the aux battery

I would strongly not use a vsr with a agm
I have seen first hand what can happen
The dick didn't have any short protection and
Got to watch his car burn to the ground.

[ag9111]

I do not use 1 on the output side of the isolator as i put one at the aux batt in the tub ..WHY.. because the cable may get hit /crunched/ cut , now if this happens and causes a short the short will travel up the line and the 50a breaker at the aux battery will trip. as soon as this happens the circut and isolator are switched off.

WRONG WRONG WRONG in so many ways.

As a sparkie I suggest that you install a fuse/CB on the output side of your isolator. In the case of a short circuit to chassis, yes your aux battery will pop the circuit breaker, but your start battery is free to delivery its full power into the short with nothing to stop it. A diesel battery, the size we have in our ute's, is capable of delivering over 5000A into a short circuit. This will get your 16mm cable cable glowing red hot and is very capable of burning your ute to the ground.
Whenever ANY cable leaves a power source, such as a battery, it should be protected in some way.
This includes winch cables. I disconnect my winch power cables, when not in use, as these are very hard to protect with the massive amounts of current they draw

[Mooons]

Just a question jet
You say the isolator won't work unless a battery is connected to is
If the cable is not cut but is damaged and shorted to ground will the isolator see this as a load & with no fuse at the isolator end keep cranking current till cable,isolator or battery fails ?

[Mooons]

I should learn to type faster

[hvac guy]

Exactly why a fuse should be no further than 30cm from both batteries + post.

[jetcrew]

Correct on all your parts guys , I will quite happily put my hand up for this one , I have confused myself after working night shift and no sleep today , I ahve no idea what thiought process I was using.

Shit all i can hope is that I would have relised my flawed brain function in a hands on .. not good Jan.

Disregard my above post and if mods want to remove it so as not to lead anyone astray please feel free to do so , i just re read what i wrote and It;s plain wrong. The isolator will need to blow up to stop the current flow if it keeps shorting on the chassis, and $15 C/B or fuse vs a new isolator is a no brainer.

Off to sleep for me, was back and forth from MM today trying to get the triton back but have a loan car in the drive way.

Time to sleep and restart tomorrow with my brain in gear.

thanks for being so easy on me guys a hey FXXXhead thats wrong would not have been out of place.

[odie602r]

Okay, so based on ag1111's input, I think the progression is:

crank batt -> short cable run (approx 300mm) to red arc isolator -> fuse/CB (after output side of isolator) -> cable run -> fuse/CB -> aux batt.

Not trying to cause an unnecessary debate here, but is something like this a worthwhile contender for the fuse/CBs:

http://www.ebay.com.au/itm/CIRCUIT-BREA ... 460727494f

there is also a 100A model. I don't really know what size (amperage-wise) to get.

[big_bob_thefirst]

U can get an automatic or manual reset one in Jaycar for a lot less:

http://www.jaycar.com.au/productView.asp?ID=SF4104&form=CAT2&SUBCATID=969#1

Something like that maybe? I don't know why they need to b waterproof but I'm sure someone may know if they have to b. I just went for something like that.

50 amp is ok. U shouldn't see that type of load unless there's a problem, I.e a short.

[jetcrew]

When I am not confuseing myself and sounding like a dick I have used these if a fuse is preferred.

http://www.baintech.com.au/fuses/bainte ... fuse-block $5.80 per fuse RRP sizes 30 - 125A avial. Size is a personal choice but I would think 50A at a minimum. Most systems rightly or wrongly have 50+.

and the holder

http://www.baintech.com.au/fuse-blocks- ... crew-mount $24.99 and you get 1 fuse Included at whatever size you want.

If you want bigger they make a MEGA version 100-500A

http://www.baintech.com.au/fuse-blocks- ... rated-500a.


Just posted as an option I have seen and used the one in your pic but have not bought off the supplier, I am not sure if the quality is different , with that type as the price seems to differ alot from different places , maybe someone knows if they are lesser quality or just a good buy.

Just don't let me anywhere near your car with no sleep LOL very

Jet

If you need small lugs to fit studs 6mm-8mm which alot of the fuse holders and c/brakers are , Narva make a good range with small openings for larger cable and nicley flared ends. part numbers.

For 16mm2 cable
57124 - 6mm opening
57125 - 8mm opening

for 25mm2 cable
57128 - 6mm opening
57129 - 8mm opening

[odie602r]

What do people think about these? I think this is what big_bob was saying earlier that they look the same as the previous link I posted but cheaper. he was right - the one in the link below is $27 and in my local shop, for the 100A job

http://www.jaycar.com.au/productView.asp?ID=SF2266

[biggibbo]

What do people think about these? I think this is what big_bob was saying earlier that they look the same as the previous link I posted but cheaper. he was right - the one in the link below is $27 and in my local shop, for the 100A job

http://www.jaycar.com.au/productView.asp?ID=SF2266

That what I have, however bought 2 for $30 delivered from the USA via Ebay. Cheaper again if you can wait a few weeks for delivery.

[big_bob_thefirst]

No, I actually meant

http://www.jaycar.com.au/productView.asp?ID=SF4104&form=CAT2&SUBCATID=969#1

They're the Chassis Mount Autoreset Circuit Breaker 50A 12VDC. (last item on page 2 in Jaycar).

Only $10 or there abouts. Very basic...

[odie602r]

Sorry big_bob! my mistake.

How would one know if the auto resetting CBs weren't working, or had failed in some way? And does it really matter whether 50A or 100A - from what I understand if there's a short it will be way more than that anyway?

I did read somewhere the general rule of thumb is to have the fuse/CB rating to match cable, and I think 6B&S is about 100-125A ish??

[big_bob_thefirst]

I think the wire should b 1.4x the cb or fuse. So a 100amp should have 140amp rated cable. It's all safety factors at that level. And it gets a lot dearer...

My set up goes thru a cteck dc charger, which limits the current I guess. A 75 or 100 amp cb would b fine as well.

As for failing, not too sure. I'll have to read up on how they work. Would imagine they're pretty fail safe as they are temperature driven...

[odie602r]

So sounds like 50A fuse/CB would be okay? I was only thinking 100A as that was what the common word on the street appeared to be.

I'm happy to put on whichever is most appropriate.

[jetcrew]

Odie,

I,m pretty sure the auto reset type as in the jaycar picture , use some sort of bi-metalic strip , when it heats up it bends and breaks the contact, thus breaking the circut. Once the circut cools down IE fault rectified the bi-metalic strip will flaten back out and reconnect. at least thats how it was explained to me, so even though the term is auto resett the fault needs to clear before it will reconect.

Jet

[ag9111]

Problem with the auto reset units is that they will reset back onto the fault and trip again. Cool off and reset back onto the fault again. Cool off and reset back onto the fault again. Cool off and reset back onto the fault again. Get the picture, till something happens like
Fault is cleared
Battery fails
CB fails
etc etc.
Not a real fan. As an industrial sparkie who has dealt with AC and DC power for nearly 25 years now, I still believe that a fuse is the best method of clearing a DC fault, even on 12V. I have seen these little DC breakers fail on cars before, resulting in burnt out wiring. Luckily the only damage done.
Apart from cost, why do you think that car manufactures still use fuses?
After saying that, I have two auto resetting CB's in my Ute that I must really change out. I will be going fuses.

[Mooons]

Okay, so based on ag1111's input, I think the progression is:

crank batt -> short cable run (approx 300mm) to red arc isolator -> fuse/CB (after output side of isolator) -> cable run -> fuse/CB -> aux batt.

Not trying to cause an unnecessary debate here, but is something like this a worthwhile contender for the fuse/CBs:

http://www.ebay.com.au/itm/CIRCUIT-BREA ... 460727494f

there is also a 100A model. I don't really know what size (amperage-wise) to get.

everyone will see things different
But I would prefer to put the fuse/CB before the isolator not after it as the isolator is still a device that can fail
If it burns out or shorts to ground you still have the same problem
No protection

[odie602r]

Not a real fan. As an industrial sparkie who has dealt with AC and DC power for nearly 25 years now, I still believe that a fuse is the best method of clearing a DC fault, even on 12V

What are your thoughts then on manual reset circuit breakers, just out of interest Garth?

[jetcrew]

Like you I fully respect that everyone has different opinions and I certainly don't want to be starting a debate on the subject that is detrimental to the forum but it's always healthy to have disscusion and if that disscussion is leading towards knowledge for members then it's a win win . I have even done a full 180 on subjects based on information from forums . healthy respectful debate should be encouraged.

I have always thought that underbonet stuff needs not have breakers or fuses, after all the alt pumps straight into the crank batt on many cars withoiut a main fuse, some cars come standard with 2 batts that are just connected , so I have quite comfortably and have now in my trition no fuses between the crank batt isolator and aux batt. but as soon as the high current leaves the engine bay then yes it needs protection.

It would take a pretty big impact to cut or short the batts under the bonnet and if that was to happen then the isolator would be the least of my worries. And the cables are so small in length given the loication of the 2 batts in the ML. But with the aux down the back then 100% agree with the others that protection is needed as the high current has left the relative saftey of the engine bay.

Just my thoughts and I am quite comfortable doing it this way and have seen many set-ups the same ,the big factor seems to be distance between batts and location of cables . But if in doubt add the protection , because if it's not on it's not on

Jet

[big_bob_thefirst]

Jet, I agree. U have to take the risk of cable breakage into account. If its all under bonnet and protected there, it should b ok. It's when it goes in or under the truck.

I would prefer the manual reset but they didn't have one there. U can get those small thermo ones with a manual reset button.