Third Battery in Trailer

Sean S

I have a third battery in my camper trailer. It is connected in the way you describe above. I have a Rotronics isolater that was on the car when I bought it. I have spoken to Rotronics, about 4 years ago, they said the isolater will not do the job and that it will fail. So far it has not.

I believe the secret is in maintaing the trailer battery when it is sitting in the shed at home for months without being used.

The problem most people have with trailer batteries is that they are just about cactus from lack of maintenance. They are then pressed into service and expected to work perfectly.

I have a small solar pannel which I bought at BigW for $35.00. It is plugged into the cig lighter socket of the camper all the time. The battery that is currently in the camper cost me $4 at the tip about 3 years ago.

Duncs

Sean,

I too have a Piranha dual battery system. (DB-150S)

I also have a third battery (portable that sits in the back of the Jack and is charged by a separate charge controller, connected to the auxiliary battery.

The Piranha isolates the other batteries until the starting battery has obtained full charge, then switches over to enable the alternator to charge the auxiliary battery and any other battery on that circuit.
The separate charge controller ensures a sufficiently high voltage is applied to the third battery.

A common solution for your exact circumstance is by the use of an Arrid Twin Charge controller which can be located close to the battery in the trailer. This increases the voltage at the battery, enabling the use of smaller diameter wire from the auxiliary battery terminals.

Bill

Sean,

what type and size is your "1st Aux battery" ??
Where is it presently situated ??

Mainey . . .

Sean

I have similar setup.
Mate has just finished giving me a hand to set it up, the new truck, difference is a Redarc isolator, that he had

As he explained to me..........
Keep the trailer battery the same ...as the 2nd battery that's in your vehicle.
That will make sure that there is no mis-match, in their charging and discharging ability, as you have basically charging just one battery..

ie, pure deep cycle/pure deep cycle..or as in my case.... I have 2, marine semi-type deep cycle 660cca battery's.
Now..... if you were to put in another isolator between battery No.2 and battery No.3, then they would just charge in numerical order

To the purists, I hope I said the above the right way.

Cheers
Bucky

I've heard a lot about these Redcar and Arrid things and other gismos but all I have to charge my two batteries in my caravan is a good old fashioned solenoid that isolates them when the ignition is turned off but to reduce voltage drop I have used 4aswg cable via an Anderson plug and of cause fuses either end. This system has been in operation now for the past four years and has not given any trouble. I also have a 15amp smart charger in the circuit that is used if power is available and a small solar panel that is used when the caravan is parked up for any length of time.

In an ideal world use two same sized AGM deep cycles.........no question.....

But if you can get near full charging voltage ( and by use of decent size cable, decent amps ) to the other battery ( whether it's the aux or the one in the CT ) then given time it will charge up ..

Maybe not ideal...but given the abuse most aux batts get, it will keep most people happy..

I have 6 AGM's in my CT and I don't even use an isolator, just a 30A relay, that gets switched on after approx 10mins ( to give the main time to recover from starting )........but with the use of 16mm 2 cable thru an anderson plug, the batts reach full charge ( a resting 12.9V )

But having said all that, I don't charge it off the 4x4 much because I have enough batt capacity to last most camping trips ( usually2 - 4days ) so when I get home I put them on charge with a decent 3 stage charger..

The answer is REALLY simple. For $299- you buy a Arrid Twin Charge.

Arrid Twin Charge

I've just bought a 2nd one of these units.

I've had one in the Patrol for charging the Fullriver AGM, since I bought the Chev-Nissan (it was in the rig when I bought it).

I also have 2 batteries in the camper trailer and up til now, I have just run a 6mm cable from the Fullriver via the trailer plug (a 12 pin Narva plug), over to the camper.

However, a few days ago, I bought a 2nd Arrid Twin Charge and have mounted that in the camper trailer. This means I will be getting a full charge at the batteries. FULL being the operative word.

I'm currently without my 4by (chassis being fixed). I have the Fullriver plus another (starter) battery sitting in the garage here at the moment. To test the Arrid (just mucking around in the shed), I checked the voltage of the 2 batteries with the multimeter. The starter batt was around 12.65 and the Fullriver was 13.05
I hooked the Arrid up so that the starter batt was supplying the Arrid, which was then charging the Fullriver.

Once connected, the Fullriver climbed up to 13.70 volts in a matter of 15 seconds or so, the starter battery didn't show any noticeable change.

This was a "bench" test and not real world. Normally the Arrid only works when the truck is running (wired via ignition circuit). Also, there was no load on either of the batteries. The point I'm making is that Arrid is a 25amp battery charger than runs off 12 volts instead of 240 volts.

When I ordered it over the phone last Friday (from WA....and it arrived here in country SA on Monday!!!!), the bloke asked me whether I was charging AGM or wet-cell batteries. So, you can specify the type of battery you're going to be charging.

A great unit....I have no association except for being a VERY satisfied customer.

Roachie

Thanks everyone, As usual a wealth of information.
Looks like I'm more or less on the right track.