Dual Battery Systems

[project.r.racing]

Been wanting an extra battery in the 4WD for camping etc. But they are toublesome to wire up sometimes, (well within my skill set to do it though) and to pull interior apart etc.

The back has a second 12v socket. Is there a way to charge a full size battery using this socket? Seems a much simplier solution.

Been thinking about a normal plug with aligator clips attached. But that just seems way to simple. Help?

p.s. Battery is in a plastic box with vent holes and tied down.

[Mad Mat]

there is dual abttery kits that you can buy these days that only charge the battery when its needed.

i wouldnt think that the 12 socket in the boot would have beefy enought cable for it to charget the rest of the system in your car.

may i ask why the battery is in the boot and not in the engine bay??

[ross]

I used to charge the fridge battery with the OEM rear cig lighter all the time

[project.r.racing]

Originally Posted by Mad Mat

may i ask why the battery is in the boot and not in the engine bay??

cos things like fridges etc dont fit under the bonnet, much more space in the boot.

[Mad Mat]

Originally Posted by project.r.racing

cos things like fridges etc dont fit under the bonnet, much more space in the boot.

hmm tru. but the purpose of an dual battery system is for the second battery to back up and keep the first battery charged.. that's why most dual systems are in the engine bay and they use a dept cycle battery as there secondary battery. as it wont loose charge from excessive current draw.....

[Cosmo Dude]

In theory you can charge the biggest 12V car battery from a 100mA 12V plug pack... if you have the time.
Back to reality you should visit your local FWD/Camping/Fishing shop, they have shelves of stuff just waiting to solve your dilema.

[maztech]

Hey Ryan I work at a 4WD accessories shop there are a couple of ways you can do it send me a PM with what ya got ,what car and what you are running and we will work something out


You can put a second battery anywhere in the car as long as you use the correct cable

Have a look at thumper battery packs


If you are putting your battery in a battery box in the car it must be a fully sealed battery with no possible way of venting or spilling acid --- optima battery's are ideal --- so is the thumper set up as it comes with everything and is fully portable

[project.r.racing]

i'm using the only 2nd battery for high draw accessories. will not being wired to car unless charging.

another option is to light up bonnet, hook up jumper leads from main battery to secondary battery, and run car for 15 minutes.

[Clean_Cookie]

Just buy a $100 voltage limit switched solenoid, sealed battery. Optima is good. Handles the vibrations they recon. then create a junction box with all accessories etc.onto that battery. don't waste your time if its only a weekend. just run a set of wires (jumper leads persay to the rear with a 50a fuse, power fridge from second battery unhooked for the car and then plug it in when driving etc.

[maztech]

Have a look at the redarc website has wiring options on there - run the cables from main battery under the car to the second battery wherever you mount it - use a redarc SBI12 isolator - if you are mounting it in the car use Anderson plugs to the battery pack so it can be removalable

[Cosmo Dude]

Originally Posted by project.r.racing

i'm using the only 2nd battery for high draw accessories. will not being wired to car unless charging.

another option is to light up bonnet, hook up jumper leads from main battery to secondary battery, and run car for 15 minutes.

IMO You are trying to re-invent a long established wheel.
And above I ment 4WD not FWD. Front and Four both start with F...

[project.r.racing]

sorry cosmo, my reply was aimed at matt, two more posted were added while i was typing mine.

i am trying to save a couple of hundred dollars, but guess i cannot dodge it.

[Clean_Cookie]

Short trips? I'd buy a ctek and deep cycle. Charge when at home.

[project.r.racing]

yeah thats true. another good option ryan.

or might just go plan b/original plan.

wire 2nd batt +Ve to main batt +ve is voltage isolator inline installed.
wire 2nd batt -ve to chassis.
add and andersons plug just do it is removable if required.
done.

might even attach the isolators to the batt box so only the wiring and anderson plug are in the boot when battery is not.

[Clean_Cookie]

Watch out having two main earths. You WILL get a.voltage potential between them. Quickest way to rust a car and have stereo issues. You MUST use one ground IMHO. same goes for house wiring.

[project.r.racing]

What about the folding solar panel kits? Any good for keep batterys good throughout the day without starting the car?

If a fridge uses 3.5-5.5A, then do I look for a panel system rated the same? Or it doesn't work like that?

[Clean_Cookie]

yeah that's an insanely expensive way of buying power!
assume 80% output in ideal conditions, *cold sunny day with 0 shadows),
200W panel is around 1200x750mm x0.8 =
160W, which will get you double the charge you need for a fridge, but remember, as soon as the sky is filled with clouds, even if its still sunny, output will dive to 30-40% from experience. also account for voltage and charge regulation, losing out there too, and more stuff to carry. way more expensive than a second battery and $100 isolator...

[Clean_Cookie]

not sure what panel prices are however 2 years ago we were buying them for $470ish/panel, by the container load. I'd assume you could get a cheapie for $300 now.

[project.r.racing]

seen kits for 40W/2.25A with regular and clamps for battery for $150-$250. Add another $50 for every 40W extra you add.

the fold out one that are like a suitcase with fold out legs, as everything ready to go to charge/supply power.

example:-
http://www.ebay.com.au/itm/NEW-G-P-M...item3f129c8ecd

[Cosmo Dude]

Originally Posted by project.r.racing

What about the folding solar panel kits? Any good for keep batterys good throughout the day without starting the car?

If a fridge uses 3.5-5.5A, then do I look for a panel system rated the same? Or it doesn't work like that?

Your're looking at over $200 for an 80W 12V panel and $100 for charger/controller.