Dual battery setup

[Laith]

Just put a 2nd battery in my truck.

Bought a cheap battery box, a 30 amp relay to connect the 2nd battery to the front battery when the ignition is on, battery terminals & a 3 way cig lighter socket.

Used 2.5mm mains cable from the front battery to the 2nd battery. No voltage drop with that. I already had the cable.

Battery box - $ 21.50
Relay $12.50
Battery terminals - $8.50
3 way cig lighter outlet - $8.00
Wire terminals - $3.50
Inline 30amp fuse holder - $3.50

In the short term just used the battery from the tractor but I guess when I get a decent 2nd battery it will be a few hundred.

So what ive done is connect the 2nd battery to the origional battery in parallel (via the relay) while ever the ignition is on. When the key is off the batteries are sepperated.

What can a battery isolator do that my relay is not already taking care of?

I want to know if I should spend the dollars and get one or if what I have done is going to work.

 

[joshy]

whered you mount the 2nd battery?

 

[Shonky]

Battery isolators connect and disconnect the second battery depending on the voltage at the primary battery.

For example the second battery isn't connected until the primary battery is up to 13.2 volts or better, the reason for this is to allow the alternator to charge the main battery first before connecting the 2nd battery in circuit.

Typically they also have a lower cut out voltage, usually around 12.4-12.7 volts, this allows you to use some of the capacity in the main battery for powering accessories that are connected to the 2nd battery, but the cutout is high enough that you will still have no trouble starting the car from the main battery.

 

[Laith]

Joshy: I mounted it in a plastic battery box behind the drivers side rear wheel arch. Fairly close to the tailgate.

Shonky: so the main difference between a isolator and my relay is that mine will shut the connection as soon as the key is off as opposed to when the main battery voltage drops to a certain level.

Maybe a few hours of extra power depending what you got running.

 

[D22 King]

the isolater automaticly switches the power off/on at the power voltage a relay always has power till a switch is activated ie. ignition. but if power surge in curcuit relay will disconect power.

 

[joshy]

Joshy: I mounted it in a plastic battery box behind the drivers side rear wheel arch. Fairly close to the tailgate.

inside the tub or under? im about to do my dual batt set up. and any idea the length of the cable?

 

[D22 King]

Will a battery box not go under the bonnet anywhere? on the passenger side?

 

[Laith]

I put it inside the tub Joshy. I just ran the cable off the roll but I guess your would need approx 5 meters.

I cabled tied cable along the brake lines underneath the truck and drilled a hole at the rear of the tub to give cable entry.

I used twin core cable and run the negative between batteries as well.

There would be room under the tray though Josh.

D22 King: I doubt a battery box would fit anywhere under the bonnet and I wouldnt think it could handle the heat ect.

If you want it under the bonnet just get a battery tray. About $120 though and you goto move the fuel filter out of the way.

 

[D22 King]

cheers, was lookin to get an optima dry cell and didnt really want to mount it where the back seat was.

 

[joshy]

cheers laith. Mine will be going under the tray...not keen on losing space in there and since theres no spare under there anymore theres heaps of room.

 

[mike/kerry]

I put mine in the tray here's how

wow the beers hot look at the temp

 

[Chartrock]

Mine sits in the back beside my drawers. I do have an isolator but I installed an ignition relay just to be sure. I ran 4mm wire on both + & - side and have had no problems with charging or running a fridge.

Paul

 

[Laith]

Found that the 2nd battery didnt charge enough and ran low. To much voltage drop with the cable I used.

I just removed the black conductor from the negative post on both batteries and joined it at each end with the red conductor to double the cable capicity between the Positive on both the batteries.

I just then ran a earth from the second battery to the body of the tub.

When the engine is running now the voltage drop between the front battery and the 2nd is only 0.3v.

The 2nd battery was only running at 12.7v before and now runs at 13.6v so should charge ok I think.

Took some pics to ilustrate cable entry to the tub ect.

 

[Lance S]

I put mine in the tray to run the 110lt waeco on a black widow slide and lights and whatever i can plug into the bugger. I run a trojan 115 deep cell.

 

[Laith]

Ive been battling with the second battery running flat after 3 or 4 days of running the fridge.

I guess the cable I used must have been the problem. Not thick enough.

I got five meters or red and 1 meter of black 12mm 4 gauge cable from Jaycar and fitted it today.

I also got a 200amp solenoid from Supacheap for $38.00 and replaced the relay I had previously fitted.

This has got to sort it out.

 

[Jon]

Ive been battling with the second battery running flat after 3 or 4 days of running the fridge.

I guess the cable I used must have been the problem. Not thick enough.

I got five meters or red and 1 meter of black 12mm 4 gauge cable from Jaycar and fitted it today.

I also got a 200amp solenoid from Supacheap for $38.00 and replaced the relay I had previously fitted.

This has got to sort it out.

I wouldn't expect to get more than 3 or 4 days from a battery when running a fridge. Even with no voltage drop whatsoever that is a pretty normal occurence. If you want to get a few more days out of your fridge I would look seriously at purchasing an 80W solar panel to trickle charge while you are camping. I am running a redarc solenoid with 24mm2 cable and 6mm2 back to the tray and the fridge only lasts 2 or 3 days with my 8" battery. With a larger battery you should get 3 or 4 depending on ambient temp and not much more.

 

[Laith]

I guess I didnt explain myself to well Jon...

I mean 3 or 4 days of driving to and from work and in between a few jobs. lol

Its only a small battery that Im using and its a cranking battery as well. I will get a better suited one some day.

 

[merchant]

cheers laith. Mine will be going under the tray...not keen on losing space in there and since theres no spare under there anymore theres heaps of room.

Joshy, love to see some photo's when your done. I'm considering the same thing and would love to see how easy or hard it is.

 

[Dave]

Well just ordered a dual battery kit.

D22 NAVARA TD

Laith I am making this thread a sticky as I know this question will come up often enough.

Dave.

 

[Laith]

Cool... My first "sticky".... Oh hang on.... No it isn't