dual battery for ca and caravan

Give Redarc a call..08 8322 4848

Hows it going Bob,

It will just be like charging a bigger battery . No worries .

Glenn.

thanx guys for all your prompt replies I'll let you all know how I go in a fortnight

It's not that simple. The batteries will endeavour to balance out if one is of lower charge than the other if the circuit is open. Also, if they are different types of batteries they will not charge consistently.
If you isolate them your secondary battery in the car will charge before the caravan thereby leaving the caravan charging last and maybe not being fully charged when you need it most.
My thoughts are definitely to isolate them but put a quick charger under the bonnet as a spare only and to be used last when the caravan battery is flat. Alternatively make sure the batteries are identical and be aware that they will balance up until fully charged.

Hi Bob
the Redarc relay parallells the crank bat & the van bat AFTER the crank has charged to approx 13.2v. The alternator then continues to charge both batterries in parallell.
Adding a 3rd bat simply means you now have 3 bats in parallell.The batts should be the same type ie 3 wet lead acid or 3 agm , but need not be the same amp/hr rating, & you can mix crank & deep cycle. [use heavy 6sqmm cable not 6mm auto cable as a mininum between redarc & aux in 4by]
The main problem with your set up will be that the crank & aux in the 4by will be charged while the van battery will not be charged to the same extent due to voltage lost in the long run of cable to the van batt.THIS is COMMON PROBLEM WITH ALL VAN BATTERRIES UNLESS A SPECIAL CHARGER[OPEATING OF 12V] IS USED THAT BOOSTS THE VOLTAGE & CONTOLS THE CHARGING OF THE VAN BAT.
The only other way to minimise the under charging is to use the heaviest cable possible [ positive & negative] you can between the van bat & the Redarc relay
The 2 aux batts will equalise & discharge to the same level over time if in parallell .

Bob,
Yes, you can install another deep cycle battery in your 4wd and run it in parallel to the caravan battery.

Alternator-> (CRANKING battery)-> Redarc-> (4WD battery)-> (VAN battery)

“Cranking battery” is fully charged first, causing Redarc to close the circuit, forcing all three batteries to be charged as ONE large battery.

Mainey . . .