Dual Battery in tub

[bgorm6]

Alright few questions here for the experts.
ive got a 120 a.h deep cycle power sonic battery going into the tub with a projecta 150amp dual battery isolator going under the engine bay.

what size cable is best for the job as i dont wont any voltage drop ?
what type of relay or fuse do i need for the two to be connected ?

Thats all i can think of at the moment,
thanks in advance, Brydon.

 

[happy john]

as heavy as possible neg to ground is ok i used welding cable 12mm preferably a cable from your neg on battery don't forget circuit breakers front and rear and fuse everything.

 

[Old.Tony]

Unfortunately the First Law of Thermodynamics plays here too. On any electrical cable, you will ALWAYS have voltage drop. Simple fact of physics. Electrons propagate along the cable from atom to atom and it takes energy to do that, which is given off as heat (that's why fuses blow - too much current causes the heat to rise too high and the wire melts).

To minimise it, use a good conductive cable (multistrand is great stuff and perfect for mobile applications as it's far more resilient than single strand). The heavier the cable the better. Aluminium cable (like some weld flex) is a great conductor but aluminium is more brittle than copper and fatigues sooner. If you can keep it still (tied to the chassis, for example) then it's a great choice. Otherwise, 4Ga or heavier is what I'd recommend for reducing voltage drop.

 

[Jaybird]

I have just done this exact same job on my Nav and used 6 B&S cable which is heavy twin cable. I wired it so that it a earth return back to the main battery. I have a 2 x 100 amp fuses 1 at each end of the positive cable.

 

[wildlifeDriver]

Try using a dc-dc charger instead of a battery isolator as they charge your system better than alternator . and you can run smaller cable

 

[rescue]

Try using a dc-dc charger instead of a battery isolator as they charge your system better than alternator . and you can run smaller cable

If you are putting batteries in the tub DC-DC converter is the cheapest option what you pay extra for the converter you will save in cable costs and early battery failure prevention...

 

[bgorm6]

thanks for the response

 

[Joshp82]

If you are putting batteries in the tub DC-DC converter is the cheapest option what you pay extra for the converter you will save in cable costs and early battery failure prevention...

I'm looking to do this asap. I would just like to be told exactly what to put in.
Does the dc-dc converter work instead of a dual battery isolator? How does it protect my starting batteries? I am just going to add a 3rd battery to my tub. I will most likely have an 80ah battery in a box at the cab end. All it will run is my fridge when camping and some LED lights.
Thanks Josh

 

[RustyNav09]

Dc to dc will run instead pf the isplator. The dc should do what the isolatpr does by cutting power to thestarters whe they reach 13.4 or something. Put a fuse at each end as you would on you isolator.

 

[Joshp82]

Do you know if I can add solar panels too?

 

[Joshp82]

Would something like this be ok? http://www.ctekbatterychargers.com.au/ctek-d250s-dual.html

 

[Oilad]

Yea mate i have one an that will do ya. Still looking at just a small 10w or 20w panel to throw on my roof rack to keep it toped. But for camping i have 160w which pretty much keeps it goin..

 

[Oilad]

Ebay u find them a bit cheaper too

 

[Joshp82]

Awesome thanks. Ill keep an eye out for one. I need it sorted by the start of April.

 

[Jaybird]

I have a 130 amp/h battery in the tub, this wired through a dual battery isolator in the engine bay using 6b&s twin core cable with earth return and 2 100amp fuses at each end of the positive cable. On the roof of the canopy I have 120 w solar panel also wired into the aux battery. I have just returned from a trip of 6 weeks from Vic to Cooktown, we freecamped most of the way and used this setup to run a 45ltr Engle fridge as a freezer to supplement our
Caravan fridge. On 6 nights we were in showgrounds and on power and I used this time to hook the aux battery onto a charger. We had no problem with this setup and returned home with a freezer full of seafood.

 

[RustyNav09]

Josh. I have that exact charger and it is bloody brilliant. I use a solar panel without a regulator. Run it to the ctek and it regulates the power and charges the battery. I've had 180w running into it with unregulated power at 22volts. Best charger on the market I reckon

 

[Joshp82]

Awesome thanks rusty. Ill buy one soon. Any tops.n what battery to get? I think Ill only need about 85ah to run my fridge. It will only run a coupe of LEDs as well.

 

[RustyNav09]

Whstever suits you. I have a SSB 100ah agm deep cycle and a kickass 120ah agm deep cycle. The ssb is better by far. Comes down to what $$$ you wanna spend. I have heard the Discover agms are a great piece of gear and around the $200-250 mark

 

[Joshp82]

Is this similar to the ctec? http://pages.ebay.com/link/?nav=item.view&id=290872792801

 

[Old.Tony]

Is this similar to the ctec? http://pages.ebay.com/link/?nav=item.view&id=290872792801

Not really. The C-Tek D250S takes two inputs and chooses the better supply to source power for its charging. This means you connect it to your alternator (main battery) and your solar panel and whichever one is putting out more power gets used. At night, that's the alternator - during the day it's either.

Even the D250S has issues with the "smart" alternators. This ebay seller hasn't got it 100% right - these alternators don't just drop the voltage at idle, they can drop it at cruise as well.