2 Batteries parallel?

[Family4x4]

I am yet to buy a dual battery setup, I will most likely go with a DC DC setup.

In the meantime I have a second battery sitting in a decrepit Hilux doing nothing.

My question is can i put the second battery in the car and wire it in parallel to the cranking battery. It is also a cranking battery.

I can then put the fridge on it.

Is my only concern that my accessories may run my main battery flat, or will there be other problems. Is this even possible.

Cheers

[threedogs]

I would put it in a battery box [plain] and then you can charge it via a cig outlet if need be.
Not ideal for running the fridge but I know the story, It may last a while

[BillsGU]

You would be wasting your time and effort. Do it properly the first time. Flat batteries in the middle of no where are not a lot of fun.

[the evil twin]

I am yet to buy a dual battery setup, I will most likely go with a DC DC setup.

In the meantime I have a second battery sitting in a decrepit Hilux doing nothing.

My question is can i put the second battery in the car and wire it in parallel to the cranking battery. It is also a cranking battery.

I can then put the fridge on it.

Is my only concern that my accessories may run my main battery flat, or will there be other problems. Is this even possible.

Cheers

No reason at all why you cannot do that altho a second Cranker isn't exactly ideal for running the frig or other "house" apllications.

If the batteries are close together IE in the engine bay using "battery" cable to connect then there is not much point to a DC/DC setup.
They are predominantly to compensate for voltage loss over long and lighter gauge cable runs.
Commonly that is from the Engine bay to a van/camper, different battery technologies between Cranker and House or in situations where the House requires higher charging voltages or has lower internal resistances and would otherwise steal the Alternator output from the Cranker .

If you are at all worried about pulling down the Cranker then a simple battery post mounted manual Isolator (they have little thumb wheels or somesuch on them)on the house battery feed in would allow you to protect the Cranker until you install the full kit.
That will allow you to do your wiring etc in the interim.
You will need to remember to open/close the circuit but taht only takes a couple of seconds
Don't forget to allow for the mounting of the chosen Isolator, if it is a DC/DC it must be as close as possible to the House or again there is little point. If it is a "standard" isolator it should in theory be as close as practicable to the Cranker

If you are not winching or cranking off the House Battery seriously consider circuit protection at each positive terminal and you can use much smaller gauge wiring.
If you are winching/cranking then you need heavy gauge wiring and circuit protection will be quite expensive and is often not used on the interconnect BUT the cable route and cable protection is given serious thought.

No matter what you end up with I would fit a dual sense Isolator such as a Redarc SBI12D or equivalent.
I use a lot of Intervolt programmable isolators but they are more expensive and an overkill for most reccy users.

Dual sensing is much more versatile and means that if the Isolator detects a charging source on either battery (Alternator/Solar/Charger/etc) it will interconnect both batteries OR if it detects either battery going low it will disconnect the other.
If you do (or plan to do) a fair bit of camping I would definitely go that way.

[the evil twin]

... I should have added that when my Patrol with the "Fortress of Evil" hanging on the tow bar are rigged for war I have 500 amp hours of battery capacity.
Any battery can be charged from any "source" or interconnected to power any system.
I can use the Camper to start the vehicle if needed or if I am camped up and my Solar is deployed, Mains available orGenny running, I plug the vehicle into the camper then the Battry Management will also charge the vehicle.

All that I use is 2 dual sensing Isolators (Cranker to House and Camper to Vehicle) a Solar Regulator obviously and a manual battery selector switch (to choose which Camper battery bank).

I have set it up that way because I have frig's in the Vehicle and the Camper and the only thing that pisses me off more than a flat battery is warm beer.
Since using this configuration E.T. has been one happy camper BUT what works for me won't necessarily suit everyone

[MudRunnerTD]

Before my last trip out in the GQ the other week i ran a Hot wire across the back of the fire wall and bypassed the Redarc. I also ran another earth from each of the 2 batteries to the Motor.

I was setting up for an Epic Winching weekend and needed everything i could get to the winch. Worked a treat for the weekend but would not tour like that. Might consider installing a switch into that if i got serious but will be ripping out the second battery in the coming months and setting up a 24v alternate system for the winch duties. When out in the GQ it does not sit for long anywhere though so the fridge will not drain too much. If needed i would unplug the fridge anyways The GQ TD42 will run on a Dead battery so all good, dont turn it off though!! I have been so flat that it would not play a CD while driving and my Headlights would not work! 3am on an extreme trip and no headlights was average though!!! Fun and Games! the things you do.