Another question on battery isolators

Submitted: Sunday, Feb 17, 2008 at 19:04

ThreadID: 54674 Views:2278 Replies:6 FollowUps:1

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brushmarx

Yeah, I know, it's all detailed in the past posts, but there's so much info I've confused myself.
I have a camper trailer set up with 2 batteries and an Anderson plug connection to the car.
The towing vehicle, 99 Jackaroo petrol has one battery.
I figure I need to fit a battery isolator near the battery, and run the power and earth to the trailer.
I guess I can power a ciggie lighter in the rear of the Jackaroo for a fridge while driving, and then the power and earth continue to the trailer.
If this is correct, the main battery will recharge first, then the isolator will cause the trailer batteries to charge while providing power via the ciggie adaptor to run the fridge.
Am I right so far???
The main question, if I have the rest correct, is about the isolator if no trailer or fridge are in use.
Does the isolator need to be turned off to stop all the electricity running to the Anderson plug with nowhere to go, or does it not matter?
Cheers, and apologies if this has been covered before.
Ian

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Reply By: oldtrack123 - Sunday, Feb 17, 2008 at 20:03

Sunday, Feb 17, 2008 at 20:03

Hi
The main battery charging 1st depends on the type of isollater you have,if it is aredar c relay type the main will charge but if it is asimple diode type the flattest battery will take the charging current till they are at equal voltage.
If nothing is connected then no power is used /it 's not a pipe that you have to sh ut a tap on.

AnswerID: 288005

Reply By: obee - Sunday, Feb 17, 2008 at 20:07

Sunday, Feb 17, 2008 at 20:07

The isolator is there to stop you running the cranker flat. If you want the alternator to charge the trailer batts you will need some heavyish wiring. I keep a battery in the back for the fridge but I use a gennie when I am stopped without a 240v outlet to keep the charge up. I can get about fifteen amps down the wire which is not enough. I must get around to poking some more wire through the body channels.

Owen

AnswerID: 288007

Reply By: Member - Tony W (VIC) - Sunday, Feb 17, 2008 at 21:02

Sunday, Feb 17, 2008 at 21:02

What you are saying is basically right

"The main question, if I have the rest correct, is about the isolator if no trailer or fridge are in use.
Does the isolator need to be turned off to stop all the electricity running to the Anderson plug with nowhere to go, or does it not matter?"

It does not matter. When the Anderson plug is disconnected think of it as a switch turned off. No current will flow and therefore you dont have to worry about the isolator when there is no trailer.

Tony

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AnswerID: 288015

Reply By: Mainey (wa) - Sunday, Feb 17, 2008 at 21:07

Sunday, Feb 17, 2008 at 21:07

""I have a camper trailer set up with 2 batteries and an Anderson plug connection to the ... towing vehicle which has one battery. I figure I need to fit a battery isolator near the (CRANKING) battery, and run the power and earth to the trailer. Am I right so far""

Use an automatic battery isolator that will charge the CRANKING battery first. Then charge the two batteries in the Camper.

The (+) power cable runs from the Alternator to the existing CRANKING Battery, to the Battery ISOLATOR, the Anderson plug and then the TWO batteries (wired in parallel) in the Camper.
The two Camper batteries should be earthed at the Cranking battery earth.

Mainey . . .

AnswerID: 288017

Reply By: Sand Man (SA) - Sunday, Feb 17, 2008 at 21:42

Sunday, Feb 17, 2008 at 21:42

The best solution for your situation Ian, is an Arrid Twin Charge controller.

This will limit the need for heavy duty cable from the vehicle as the Twin Charge takes a lower voltage and boosts it before it is allied to the remote batteries.

The biggest problem in your scenario is voltage drop due to long cable runs.

Arrid Twin Charge Controller

Bill

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AnswerID: 288044

Reply By: Derek from Affordable Batteries & Radiators - Sunday, Feb 17, 2008 at 21:49

Sunday, Feb 17, 2008 at 21:49

Hi Brush

You are on the right track.

Fit the isolator under the bonnet and use good size cable 6 B&S is most commonly used.

The Arrid-twin-charge has its uses but not for 2 batteries as they are only rated at 20 amps and you can get around 40 amps through a 6 B&S cable to two 100 a/h AGMs in a camper. My own van is set up this way.