Komodo wrote:The isolator controls the charge distribution (rather crudely - but it does it) so your main battery will be "fully" charged before your auxillary starts to get charged. Take for example this senario:
You pack up camp hook the trailer up with a battery thats been flattened right down - its 120Ah, your car battery is 45Ah -and you've started driving - but then pull over within 5 minutes cause you want to have a look at something. Your alternator hasnt even had enough time to fully charge your main battery - let alone start thinking about charging a 120Ah deep cycle battery - but the batteries are parralleled and have just equalised voltage (possibly as low as 9-10 volts) you come back to your car 10 minutes later - the car doesnt start because the voltage is too low to opperate the starter solinoid let alone have enough current to turn the starter motor which requires a heap of current to produce the torque req'd to start the vehicle.
The reason being is that if you connect the trailer to the car then start the car - you may have dropped the voltage to low to start the vehicle because the batteries will try to equalise the voltage difference.
The other thing an isolator does is it prevents to high of an inrush of current. IE is the trailer battery is dead flat and you connect it after the car is running (so you dont have the above mentioned equalisation issue) you could spike your cars electrical system, you could damage your main "start" battery by putting an excessive high current draw with no limitation. You could also damage your campers battery by allowing it to take charge quicker than it should (a problem especially with AGM and spiral cell batteries).
Realistically you probably don't "need" an isolator - but personally for what $120 i think its pretty good insurance. Theres also that slight possiblity that you MAY one day forget to disconnect the trailer from the car because you dont need anything from the back of the car...
Also many people will have a "start" battery and an "auxillary" battery in the car as well as a battery in the camper - they might even use an anderson plug to anderson plug extension lead to keep the auxilary and the trailer battery parralleled to give them a greater reserve capacity
Derek wrote:When I bought the solar unit the sparky from the shop talked to me about putting in a charging system similar to to a duel battery system. What he emphasized is that when I go somewhere at least I will arrive with the battery on the trailer fully charged. Not only that, a couple of days of heavy rain and dark cloud and the solar will be limited. I can then connect to the car and run it for a while.
Today I ordered the following kit from Derek Bester at Sidewinder http://www.sidewinder.com.au
Will I ever stop buying stuff for this camper.
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