Dual Batteries (L series wagon)

openflame06 · Post by **openflame06** » Wed Apr 29, 2009 7:53 pm

Hey everyone.

Just wondering how I should go about putting in a second battery in my wagon. I've heard of people doing it but i was just wondering how its wired in to the alternator so it charges as well as the main battery.

Also just want to know where a good spot to mount the secondary battery is and what type I should use (e.g. deep cycle)

I would mainly use the second battery for running 12V stuff like inverters and possibly a fridge for camping.

Thanks

YouTube · Post by **El_Freddo** » Tue May 05, 2009 10:58 am

Best place to talk about batteries that is best suited to your application is a reputed battery shop or your local parts supplier if you know that they know what they're talking about

Battery location: I've seen two different setups: First one was a factory job on a touring wagon - the second battery was a small standard sized battery mounted over on the driver's side directly behind the headlight parrallel to the radiator.

The second setup I've seen is two standard family sedan sized batteries mounted side by side parrallel to the radiator in the original battery space - its a very tight squeeze though.

Another one you can use if you've removed the spare wheel is a gell or dry cell battery mounted on its side in the spare wheel well under the bonnet...

Use a dual battery isolator system to charge/use the batteries - this will allow use of one for accessories that you've mentioned while keeping the car's battery fully charged so it'll start when you need it to no matter what the other battery is doing. Once both batteries are near the same charge level I believe the isolator will open the two batteries to charge together. I'm not entirly sure about this as I've got a very basic understanding as to how these work at the moment.

Hope this helps - if your unsure about any products offered to you do not be forced into a buy until you know its exactly what you want/need... Do some research if you feel the need.

Cheers

Bennie

AndrewT · Post by **AndrewT** » Tue May 05, 2009 1:09 pm

Realistically most people with L series won't want to spend a great deal of money on a dual battery setup so it's good to opt for a basic switch rather than the more expensive active setups. These switches cost about 40 or 50 bucks....closer to 70 I suppose once you buy the extra battery leads to go with it.
If you're car is EFI it's a good idea to put a surge protector in-line to help protect the ECU against possible spikes.
I had one in my old wagon, it worked great. The switch is quite a large round device which sits in the engine bay and has 3 selectable positions - Battery1, Battery2 and BOTH.
I ran mine on BOTH pretty much all the time.
When I wanted to go camping I switched it to Battery2 (which was a fairly large deep cycle battery). I could happily drain that down to nothing over night then just switch to Battery1 to start the car up.
Then I'd switch back to BOTH so it charged both batteries back up again.

They look kinda like this, except mine didn't have an OFF position like this one.
http://www.sleeoffroad.com/technical/images/db1.jpg

In my wagon I had a normal sized battery in the normal position of the engine bay, stock. The larger deep cycle battery I had on the opposite side of the engine bay (drivers side). There is a bracket there originally which I cut out. I bought a standard metal battery tray and mounted it there - looked totally factory.

I really must get around to re-doing this setup in my current wagon! Although I may actually spring for a propper managed system this time. They have the advantage of a much better charging system when charging both batteries.

GOD · Post by **GOD** » Tue May 05, 2009 4:03 pm

AndrewT wrote:Realistically most people with L series won't want to spend a great deal of money on a dual battery setup

+1

In my Falcon I ran a wire (actually the power lead from an amp kit) off the positive post of the primary battery through a fuse then a 75A relay, to the positive of the secondary battery in a box in the boot. Negative terminal of the aux batt was grounded to a convenient bolt. The relay coil was connected to the ignition. Then power your inverters, fridge etc straight off the aux battery.

The only issue I had was that on starting the engine with the secondary battery fully discharged, there was a large inrush current to the secondary battery, which could blow the fuse. A decent battery (which doesn't easily run right down), or higher-rated relay and fuse would have fixed this.

As for location, I'd be aiming to put two batteries roughly where the stock one fits. Or if you want to do a bit of fabrication, there's some wasted space under the stock battery:

Dane.

tex · Post by **tex** » Tue May 05, 2009 7:25 pm

The Early falcons used to have a remote mounted solenoid which I've seen used before and are for sale at super cheap for cheap! also I would recommend an optima red top battery as they are compact and robust, But for a respectably (Not a real word I know) cheaper option just go a normal deep cycle battery.

discopotato03 · Post by **discopotato03** » Wed May 06, 2009 10:24 am

I used to use an Odyssey deep cycle battery in a car that had a very cramped engine bay (twin cam EFI conversion) and a couple of those may just about fit in the std L series battery location .

I reckon a starter solenoid may make a cheap "switch" and easy to trigger .
Need a sparkys opinion though .

A diode switch is the best way though expensive I'm told .

Cheers A .

vincentvega · Post by **vincentvega** » Wed May 06, 2009 11:18 am

Diode isolators are crap due to the associated voltage drop across the diode.

A starter solenoid is no good due to the amount of current it pulls to remain engaged.

Use a proper voltage sensitive relay like a Redarc. http://www.redarc.com.au/smart_battery_isolators.htm

A few other companies make similar ones as well.

I use 6 Guage cable to connect a Redarc SBI12 isolator to a 75AH Absorbed Power AGM mounted in the cargo area. I have a 60A fuse at each battery for safety. This has been an awesome setup for running my fridge and other crap and has never given me a single issue.

Redarc gear can be picked up for cheap off ebay....

Xtreme_RX · Post by **Xtreme_RX** » Wed May 06, 2009 6:07 pm

I agree with vincentvega About the diode isolator. I used to sell / fit battery isolators every day.

I will take a photo of my dual battery setup....

openflame06 · Post by **openflame06** » Mon Aug 31, 2009 7:14 pm

Its been a while since ive been on the forum, thanks for all the info its good to hear what others have done and reccomend.

Very appreciated