Two Battery Isolators...Is this the best way??

G'day Garth,

From my reading up on things - as I wish to do 2 off agm's in the rear of the Jeep - I think that you would use another redarc off the second battery. This will establish a charging priority order of start battery - second battery - then next bank in the Kamper.
Also the second battery will be isolated from the Kamper bank then and will not be drained if the Kamper bank goes flat.
I have been looking at doing 2 x 120 A/h agms in parallel for the back of the Grand Cherokee to be used only for camping and both being portable in a plywood box each - or can bang them in the Sportstrailer roadrunner luggage trailer. Although these will only go off the one redarc. Only problem I have wwith this, is that the existing cig lighter sockets are wired direct to the main battery and I have difficulty seeing how things will work when I remove the second battery supply (ie disconnect the anderson plug) as the redarc will automatically switch over to something that is not there as it only checks the start battery, and as a result, if say my phone is charging, or a laptop is on, or even fridge is in and on (due to only using for the day and not needing the second setup in), then do these things actually still get power?? If ya know what I mean
Cheers
Graeme

Garth posted,
"My question is.....Anyone who have done this or do you just operate with the one Redarc in place?
Has this caused any problems"

Garth, Use an ELECTRONIC battery isolator that is guaranteed (in writing, by the actual isolator manufacturer) to work with DIFFERENT types and styles of batteries, and you will have no problems.
Does it say anywhere on the Redarc installation literature that they are guaranteed to work with different types and styles of batteries, if it's not there in writing ask "why not" when the manufacturers of "Electronic" battery isolators actually supply a written guarantee with their products and state no matter what type and style of battery is used the Electronic Isolator is guaranteed to work perfectly.

Read some forum posts of ppl having problems charging their DEEP CYCLE battery and see what type of battery isolator is being used, a MECHANICAL SOLENOID is usually part of the problem - not an electronic battery isolator.

Garth,

I am not familiar with the range of Redarc products, but what you need to ensure, is that you do not have a voltage drop at the Camper end.

I would leave your current dual battery setup as is.

Assuming you have a heavy duty cable running back to the Camper, (via Anderson connectors at the rear of the vehicle) I would look at installing a "booster" type of charge controller in the Camper.

The Arrid Twin Charge unit allows exactly for this situation.
The DCTC20 for instance, provides for an input voltage between 8-15 VDC and is commonly used on many Camper Trailer and Caravan installations.

There may be a Redarc product that does a similar job, but the Twin Charge is well known in the Caravan/Camper Trailer Industry.

Hi Garth,

I have a similar setup, dual batteries in the Patrol with a redarc isolator and a 100a/hr battery in the camper. I run a cable from the 2nd battery to the camper, but have a relay in-line to manually overide when its charging. This setup has served me well and avoids the expense/complication of a second redarc isolator.

I have an indicator in my Patrol that shows when the redarc is isolated. In practise it is rare for the the isolator to be on for longer than 10 seconds after starting the car. In actual fact, I have never seen it on longer than 30 seconds. Also, having a switch in the line rather than another redarc means I can use the 2nd battery in the Patrol to compliment the 3rd battery in tha camper if I choose to.

The only downside of this setup is that the 3rd battery will never receive as high a voltage as the others due to line losses, regardless of the type of isolater you use. Given you have an AGM battery (likes higher volts again) then you would be best off adding an Arrid Twin Charge in the camper (as Sand Man says above) as this boosts the voltage up, thus ensuring you give the AGM batteries the best chance of a full charge while travelling.

I use a 240V 3 stage smart charger to fully charge the battery on the camper before I go and use the vehcile to simply top up as we travel. I doubt I would ever get the camper battery back to more than a 80-90% charge while travelling with my setup, but this is fine as they get fully charged when back home on 240V.

Cheers

Captain

As has been pointed out several times it is voltage drop in a long 12v. run that causes more problems than isolators. If you have 14.1v. at the alternator (high end of normal alts) it is very easy to find 13.5v. at the battery "down the back". Only 0.6v. loss, but it means you will never attain more than 75% charge.
More and more people are using a (say) 350w. 12/240v. inverter under the bonnet, then running a 240v. lead to a conventional (say) 240/12v.10a. charger with float control.
Properly installed, the 240v. supply should not cause any safety concern, and you always have FULLY charged batteries.
furph

My only concern could be if you have no monitoring system you can see/check is that if your aux (2nd) battery dies then you may never charge your KK batteries, where if all the aux batteries were being charged with some form of isolation between the vehicle and trailer batteries you would at least have charged batteries in the camper

The main problem is that the 350 A/H of batteries in the KK, even ordinary wet cell batteries, could easily pull over 100 amps while charging and AGM type batteries will pull even more, so with this type of set up, the alternator will not only not be able to charge everything up without driving for 10 to 15 hours straight but the alternator is going to have a very short life span as are the batteries because they will never be charged properly.

One alternative might be to fit a second alternator dedicated to just charging the KK batteries, but even this, depending on how low the KK batteries are when you set out for your drive, could take may hours of driving, but still a lot less driving time than trying to charge all the batteries off one alternator.

Cheers and just a suggestion

Hi Garth
Apologies 1st off as I'm not answering your post but actually requesting some info if you don't mind?

I have just taken delivery of a new Toyota Prado TD and soon to take delivery of a KKaravan. I was wondering if you can advise me if you did your 2nd battery install yourself and if any tips etc. I'm an electrical mechanic however when it comes to 12v I find its a slightly different world/thought process.

Went to ARB today and the $900+ to have 2nd battery installed and wired for an Anderson plug at the back sounded far to expensive for me.

Also KK supply the electronic actuator for the Karavan. Did you get one of these and if so did you fit it or have it done by that BIG company call "By Others".

Thanks

PeteS