Change of setup for Dual Battery

[FrootStik]

Hey guys.
I know there is a lot of threads around regarding dual battery systems, but my question is a little bit different.
Hoping to get a little help from someone who knows there stuff about Dual Battery systems.

I got mine installed a while back, with a InterVOLT isolator, with the dual battery being in my tray inside an Arkpac 730.
So the isolator connects to the Arkpac using the anderson connection on the arcpak box which I believe has its own smart charger inbuilt.
Im looking at changing this to a normal dual battery setup, not a portable arkpac setup.

So, if i disconnect the anderson plug from the arkpac, put in my choice of dual battery. I'm wondering if i could just connect the battery via anderson lead, to the existing anderson lead in my tray, which connects to the isolator.
Do i need a charger? Do i need fuses? This is the part i have no idea about.
Or do i just connect it straight up to my anderson plug, nothing in-between the battery and isolator.

Hope i can get this cleared up.
Cheers all

 

[happy john]

So you would like to completly remove the Arkpac and start with a fresh setup in the tub?. Are you comtemplating a Ctek DC/DC?, what you propose to do will work if the wireing from the isolator to the anderson in the tub is able to carry the amps the Ctek needs to work properly. As the charger in the Arkpac is only a 7 amp DC/DC charger the installer may of used a cable not suitable for the 25 amps the Ctek produces. It should be at least 6mm and not earthed to the tub. Breakers or a Maxi Fuse should be fitted between the cranker and the isolator and the Ctek and the battery. It's best the Ctek is as close as possible to the aux battery, now you have a canopy it should be easy to find a waterproof location.

 

[Old.Tony]

The answer is yes, you could just hook it up, but there are a few things to be aware of.

1) Without a fuse at the aux battery end, a failure in the cable under the car could still cause a fire

2) The voltage present at the end of the cable while driving will be lower than the voltage at the starter battery. This means that you'll never fully charge the aux batteries.

3) Installing a C-Tek or similar resolves your issues particularly if it's a DC-DC+Solar charger.

 

[FrootStik]

So you would like to completly remove the Arkpac and start with a fresh setup in the tub?. Are you comtemplating a Ctek DC/DC?, what you propose to do will work if the wireing from the isolator to the anderson in the tub is able to carry the amps the Ctek needs to work properly. As the charger in the Arkpac is only a 7 amp DC/DC charger the installer may of used a cable not suitable for the 25 amps the Ctek produces. It should be at least 6mm and not earthed to the tub. Breakers or a Maxi Fuse should be fitted between the cranker and the isolator and the Ctek and the battery. It's best the Ctek is as close as possible to the aux battery, now you have a canopy it should be easy to find a waterproof location.

Cheers bud.
That's correct mate, do away with the Arkpac as the dual battery. Wouldn't mind being able to connect it up to the dual battery at some point though for charging on big trips if possible. But that's another story.

I would prefer to keep the intervolt isolator I have, as it's already paid for, and still gives the option of jumping of the dual battery if ever needed.

When you say the wire needs to be 6mm and not earthed to the tub. What do you mean by the earthing mate? Auto electrics definitely not my strong point!

With having a ctek, I know some are used instead of an isolator. So will it affect its use by having an isolator?
And what ctek would you recommend?

Thanks bud

 

[FrootStik]

The answer is yes, you could just hook it up, but there are a few things to be aware of.

1) Without a fuse at the aux battery end, a failure in the cable under the car could still cause a fire

2) The voltage present at the end of the cable while driving will be lower than the voltage at the starter battery. This means that you'll never fully charge the aux batteries.

3) Installing a C-Tek or similar resolves your issues particularly if it's a DC-DC+Solar charger.

Thank Tony

I will definitely fuse anything that needs it! Keep it properly done it what I want!

What would I need to get to do this setup properly mate?
Remembering everything is wired up correctly to my Arkpac so far.

Cheers

 

[happy john]

You can keep the isolator for extra insurance, the Ctek will isolate the aux from the cranker and is supposed to have a diode fitted to stop it drawing back though mine takes a tad of power from the cranker. I wonder if there is room in the Arkpak to fit the Ctek?, I put one in a normal battery box for a mate 4 years ago with a anderson plug if he wished to remove it. It still works well, with the earth some installers cheat and use the tub thats how you get bad voltage drop as the tub is mouted on rubber strips. If you follow the wires you should be able to trace it back and rule this out.

 

[FrootStik]

You can keep the isolator for extra insurance, the Ctek will isolate the aux from the cranker and is supposed to have a diode fitted to stop it drawing back though mine takes a tad of power from the cranker. I wonder if there is room in the Arkpak to fit the Ctek?, I put one in a normal battery box for a mate 4 years ago with a anderson plug if he wished to remove it. It still works well, with the earth some installers cheat and use the tub thats how you get bad voltage drop as the tub is mouted on rubber strips. If you follow the wires you should be able to trace it back and rule this out.

When you say the ctek will isolate the aux from the cranker. Isn't that what the intervolt isolated is doing now?
I want to do away with the arkpac, until I sort out installing a genuine dual battery. Then I will look into the 3rd battery being the Arkpac.
Just checked and the earth is ran from the chassis.
This is what I have in the tub

 

[happy john]

Yep, I thought the earth may be sus. You basicly will have two forms of isolation if you use the existing isolator and the Ctek, this is fine no need to remove anything. That wire looks ok all you need is another breaker at the rear, check under the bonnet there should be one there too. There should be a basic Ctek wireing diagram online if that will help.

 

[Old.Tony]

What John means about separate earth is good advice: make sure you run a separate, heavy gauge wire from the starter battery into the tub's system. It does NOT need to be fused. It does need to be protected from injury. The fewer joins in it, the better - go for a single heavy cable all the way down. The stuff you have looks the goods. That's the negative side taken care of - forget about it from here on in, because by doing it this way you have an absolutely guaranteed good earth (which is what we call negative, since negative is connected to the vehicle body) that you can use for all devices in the back.

On the red cable side - unless you put some form of voltage management down the back, your auxiliary system won't be as effective as it could be. This is because batteries charge better with voltages of 14.1V or more - and you won't get that on the end of the cable in the tub. Now there are several ways to do this.

1) Straight cables - obviously just as already described. It's not going to charge the battery as well as it could but it'll work and is obviously cheap. This will allow you to crank the engine from the aux batteries but personally I wouldn't ask 8Ga or even 4Ga cables to haul 500A over 6m - you'd need 0Ga and that stuff costs about $21 a metre (for a single cable, and you need 2 cables * 6m = 12 * $21 = $250).

2) DC-DC charger. If you're going to buy one, get one with a solar input. That allows you to bolt a solar panel to the roof, or have a folding panel that you bring out and connect as needed. The DC-DC charger will boost the voltage and fully charge the battery. It's a little expensive though. You have to separately jumper the aux battery to your cranker if you need to start the car from the aux batteries because you're effectively isolating the aux system with the DC-DC charger.

3) Inverter + Mains charger. This is cheaper than a DC-DC charger (you should be able to get away with about $150 for both inverter + charger). The inverter will produce 240V and run the charger as it would if connected to your house power. You have the added advantage of being able to run other gear up to the capacity of the inverter - so cordless drill battery chargers, laptop power supplies etc. Obviously nothing too big! Another advantage is that while your engine is running and the inverter is going, you can power the fridge from 240V and the battery charger will see an unloaded battery which is good.

Personally I use the inverter + charger combined with solar + regulator. Most times, the charger is never used as solar is enough (130W panel, 75Ah battery supplying power to a 60L Engel drawing 3A peak = 36Ah/day used, potentially 60Ah recoverable).

 

[FrootStik]

What John means about separate earth is good advice: make sure you run a separate, heavy gauge wire from the starter battery into the tub's system. It does NOT need to be fused. It does need to be protected from injury. The fewer joins in it, the better - go for a single heavy cable all the way down. The stuff you have looks the goods. That's the negative side taken care of - forget about it from here on in, because by doing it this way you have an absolutely guaranteed good earth (which is what we call negative, since negative is connected to the vehicle body) that you can use for all devices in the back.

On the red cable side - unless you put some form of voltage management down the back, your auxiliary system won't be as effective as it could be. This is because batteries charge better with voltages of 14.1V or more - and you won't get that on the end of the cable in the tub. Now there are several ways to do this.

1) Straight cables - obviously just as already described. It's not going to charge the battery as well as it could but it'll work and is obviously cheap. This will allow you to crank the engine from the aux batteries but personally I wouldn't ask 8Ga or even 4Ga cables to haul 500A over 6m - you'd need 0Ga and that stuff costs about $21 a metre (for a single cable, and you need 2 cables * 6m = 12 * $21 = $250).

2) DC-DC charger. If you're going to buy one, get one with a solar input. That allows you to bolt a solar panel to the roof, or have a folding panel that you bring out and connect as needed. The DC-DC charger will boost the voltage and fully charge the battery. It's a little expensive though. You have to separately jumper the aux battery to your cranker if you need to start the car from the aux batteries because you're effectively isolating the aux system with the DC-DC charger.

3) Inverter + Mains charger. This is cheaper than a DC-DC charger (you should be able to get away with about $150 for both inverter + charger). The inverter will produce 240V and run the charger as it would if connected to your house power. You have the added advantage of being able to run other gear up to the capacity of the inverter - so cordless drill battery chargers, laptop power supplies etc. Obviously nothing too big! Another advantage is that while your engine is running and the inverter is going, you can power the fridge from 240V and the battery charger will see an unloaded battery which is good.

Personally I use the inverter + charger combined with solar + regulator. Most times, the charger is never used as solar is enough (130W panel, 75Ah battery supplying power to a 60L Engel drawing 3A peak = 36Ah/day used, potentially 60Ah recoverable).

So Tony what you are saying is that the earth that's in the tub now is no good? Need to run a cable from the negative on the starter to the battery in the tub?

Then there is the wires are in the tub now, use the positive wire to connect up a dc to dc charger and from there to the positive of the battery in the tub.

Won't be able flick the switch I have in the car to use the aux as a starter if needed.
Which I have now.

I will need solar input, as I have an 80w panel and regulator, that at the moment plugs into the other side of the Anderson plug in my diagram.

So much to take in. It used to be so simple haha

 

[Old.Tony]

Essentially that's right. Earth from the chassis is potentially unreliable. It's another join, effectively, and joins can develop faults through impacts, movement and corrosion.

Starting the car - and I apologise in advance if you have the V6 4.0L petrol motor which is much easier to crank over - should draw about 500A (550A peak). You will get away with that a couple of times, but the cables (from the pics) look like about 21mm conductor cables which are rated for around 56A constant - probably 400A-500A for a few seconds if cable length is around 2m. Trying to draw that many amps over a much greater distance will not only heat the cable up but it will structurally alter the metal in the cable, leading to the risk of unreliability, failure or worst a fire. This means that the system you have now has this risk.

Already have solar? That's a bonus. I used exhaust clamps to mount the panel to the bars on my nugtop canopy's roof.

 

[FrootStik]

So Tony. Reading over your setup again. How is yours all wired up?
How does your aux battery link to your dual battery?
How is it wired up?
It's just another thing going through my head now haha.

In all honesty by the sounds of it, a dc to dc charger sounds my easiest option.
That's way I can leave the isolator, run an earth cable, connect up the charger and away I go? Is it that simple?

 

[Old.Tony]

My aux battery is my "dual" battery. In a dual battery system you have two batteries. One's the starter and one's the auxiliary. I was only being very precise about which battery I was talking about.

Yes, a DC-DC charger system is simpler, more efficient and more effective. You'll have a fully charged aux battery rather than a partial charge.

Just to show some numbers ... the alternator can generally charge your starter battery to about 75% in normal use. Over long distances, it could get to 80%. With voltage drop to the rear, let's say the aux battery will reach 75% of its capacity.

The math now is rather easy. You're missing out on 25% of the battery's capacity. For a 100Ah battery, that's 25Ah, or the ability to run your average Waeco fridge for 2*25/4= about 12 hours.

 

[FrootStik]

Ok guys. So I did some tests on the voltage I get from those back wires. When the car is running I'm getting 14.7 v at the Anderson connection in the tub.
To me, that is fine to not have a dc to dc charger in the tub, and just stick to my isolator.

Is that correct?

 

[bods]

You can, but it also depends what type of auxiliary battery tou are going to put in there permanently. Lead acid will be ok with that voltage, but I wouldn't be putting a gel battery in there with that high a voltage as you will end up killing it in a short time.

Try that test again after driving the car for at least half an hour to get the engine bay temperature up and see how much voltage the alternator pulls when hot.

In my d22, I have a 75ah flooded cell deep cycle under the bonnet and even when the motor is cold I'm only getting 14.2v at the most out of the alternator. So you shouldn't have any dramas of you're getting 14.7v.....

 

[Old.Tony]

If there was nothing using power on the cable when you measured the voltage, the measurement won't actually help. Voltage drop occurs once power starts flowing.

Grab something that will draw a bit of power (close to, or even better slightly more than what you're planning to use). Connect it to the end of the cable and measure both ends again.

If it's just a battery on the far end, consume about 50% of its charge and then measure it once it's hooked up.

 

[FrootStik]

Hey guys.
So looking at doing this mod next weekend.
Still undecided on the right dc to dc charger. What would you guys recommend?
I have read mixed things about running a dc to sc charger after my intervolt isolator. Some say they could interfere with each other. But I'm not sure how.
I understand that I won't have the ability to jump from the aux battery. But I thought that would be it.
Some say it will have a cancellation effect. As they are both volt sending products?

What are your opinions on this?

But if all is good and ready to rumble. One question I do have is. How do I connect solar and that to the dc to dc? As there is only an input for the + of the aux battery and solar panel.
Where do I run the - to?

 

[Old.Tony]

Negatives can be common. Power only flows in a completed circuit so if the positive side of the solar panel doesn't have any path to the main battery the two won't interact. In that specific case, a good DC-DC charger with both inputs (eg C-Tek D250S) will isolate the two.

What those DC-DC chargers do is take BOTH inputs and look at which is providing better power and it will switch to that exclusively until it's no longer the better source. Thus neither ever "meet" - so don't worry about that.

It's true that both starter and auxiliary batteries are "volt sending products". When the isolator turns on, the two batteries will share power - the battery with the higher voltage will send power to the lower one.

The good news is that if the alternator is NOT running, neither battery can exceed the voltage needed to turn the isolator on so they won't interact. If the solar panel brings the power of the aux battery up beyond the VSR's threshold, since the VSR measures power on the main battery side the VSR still won't switch on. When the alternator comes on, it will feed power into the starter battery, the VSR will see a higher voltage fairly quickly and will turn on, so the alternator will then feed power to both batteries. When the alternator turns off, the voltage will drop fairly quickly again and the VSR will turn off.

So no need to worry about it. Connect all the earths together. Make sure the positive cables have fuses on the cables close to each battery - that is VITAL. Can't stress that enough. Main battery - fuse - isolator - cable run - fuse - aux battery if there's no DC-DC charger. With the DC-DC charger you can forget the rear fuse because the charger won't allow power to flow back up the cable.

The idea here is to protect the cable. If the cable is snagged by anything, it could short against the chassis and provide a completed circuit for either battery which will cause a fire.

 

[FrootStik]

Negatives can be common. Power only flows in a completed circuit so if the positive side of the solar panel doesn't have any path to the main battery the two won't interact. In that specific case, a good DC-DC charger with both inputs (eg C-Tek D250S) will isolate the two.

Hey mate

The D250S was the one I am looking at.
It had one negative input.
So I run a negative cable from my starter and plug it in to that point? Then the negative from the aux also?
What about my solar setup run the positive to the solar section and the negative to the negative section?

Just a little confused on that mate. The rest is quite simple

 

[happy john]

Have a look here mate.
https://www.google.com.au/search?hl...mg..0.5.140.PH0t5VHqfrM#imgrc=8ll4soKbrM6lvM: