Hi all.. was just looking at my setup and noticed that the earth side on the van was to the draw bar, so the power wire is running to the battery is this right? would have thought that both wires would have gone to the battery, have never had problems with the car charging the van battery,
Welcome to the gang davlynh, enjoy here and out in the playground.
I have 6B&S cable coming from the battery of the tug to a Anderson Plug at the back, Poss is to battery (fused) and neg is connected to tug at back, seems to work ok.
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It seems to be normal practice to 'earth' the negative wire of the battery by connecting it via a heavy wire to the chassis at some convenient point - as in almost all automobiles these days. Therefore, as long as you have a connection between chassis anywhere and the positive wire, you have 12v.
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The Anderson plug is best served by using both a V+ and V- cable and 50A is sized to take 6B&S cable . Where vehicles have a one piece chassis it can be considered that chassis earthing can be suitable but without that chassis multiple joints in bodywork can cause losses in return voltage creating a voltage drop that can inhibit charge voltage and create inefficient charging of auxiliary batteries so where possible for a bit of extra cabling use both a positive and negative cable. Some later model vehicles have earthing points around the car that is references by the on board computer and when you connect to them where a voltage drop alternator is used the load sensed at these points may allow the alternator to raise its voltage to cover the load and this means chassis connections for earth cables are preferable. I hope this is helpful. Ian
-- Edited by powerstream on Monday 6th of October 2014 09:50:58 PM
Not doubting what you say Powerstream, but are you saying that the computer senses potential differences at the earthing points and this causes the alternator to increase output voltages? I would have thought the body mass would make voltage drop almost imperceptible from the front to the rear of the vehicle.
Most modern vehicle alternators monitor 2 voltages -
The positive voltage coming out of the alternator that is both charging the battery and running the engine electrics + accessories.
The tiny amount of voltage lost over the cable between the vehicle's battery negative and the chassis (or body). This is used to sense the instantaneous load.
They need both in order to know when and how to properly charge the battery and to comply with regulations about fuel saving.
For modern vehicles a Direct Current to Direct Current (DC/DC) converter should be used for properly charging/running any secondary loads in a trailer/caravan. The converter should be placed close to its loads and has to be connected from the terminals on the primary battery with the negative NOT to the chassis, but to the battery negative terminal so that its loading is read and handled properly by the (modern) alternator regulator. Anderson plugs are best able to connect the vehicles.
Cable size is still important, even though the DC/DC converter can change the voltage it delivers the losses in small cables are still losses!
-- Edited by bruceg on Friday 22nd of July 2016 11:18:21 AM
-- Edited by bruceg on Friday 22nd of July 2016 11:23:25 AM
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