We got our very first caravan last week, it a sprite, 20 Years old but in very nice condition
Anyway, we're taking it away next weekend for the first time so I have a couple of quick questions.
It has an auxillary plug on the van but I don't have one on the car. I'd like to fit one before we go on Friday as I don't know how good the battery is in the van.
It only has to run a couple of striplights and the water pump but if it fails I'd like to be able to plug it straight into the car.
The car has 2 huge, deep cycle batteries fitted so I'm not worried about draining the car battery and it would be nice to have that option as a back-up.
So, does the auxillary plug just have a live and neutral connection?
Also, what sort of current draw does a fridge have when running off 12 volts as I'd like to plug the auxillary in when towing the van purely so the fridge can run off the 12V to chill down before switching to the gas when on site. Is the current draw low enough that I could plug a cable into the cigarette lighter socket and run off that?
I know its a bit of a strange question but the towcar is a modified 4X4 which has a trailing lead for the towbar electrics to avoid external sockets being broken whilst off-roading so another trailing lead would be the easiest option for the auxillary connection.
You can get a split charging relay from towsure. The kit is £13.35 and part number W28. You also need the socket part number W35 £6.75.
You will need to run a wire from the battery to the boot of your car, then connect the 12 S to the relay. On a 20 year old van, however, you would need the engine running on the car to get any power from the car as the wiring would have been different to the newer vans. I am in the process of updating my 16 year old van to the new wiring.
A 12 S is not difficult to fit and could be done in an hour quite easily, for about £20. A dealer would probably charge around £150 to fit it.
TBH I don't want the option of charging the battery from the car as its easy enough to charge at home, its really just to run the lights in the van and to cool the fridge on the journey down.
With this in mind, I then only need to wire 2 lives to pins 4 & 6 and an earth to pin 3 which would give me what I need? or am I missing something
Any idea on the likely current drain of the fridge?
The fridge, on 12v between 100 Watt and 170 Watt, depending on what model. On my homepage is a detailed circuit diagram for the wiring in a caravan, you are welcome to have a look.
TBH I don't want the option of charging the battery from the car as its easy enough to charge at home, its really just to run the lights in the van and to cool the fridge on the journey down.
With this in mind, I then only need to wire 2 lives to pins 4 & 6 and an earth to pin 3 which would give me what I need? or am I missing something
Any idea on the likely current drain of the fridge?
Thanks again,
Cheers
Chris :)
You should earth pin 7 too to be sure it would work. The downside of this though is that just running a supply directly to these pins means that the fridge is going to be draining the car battery whenever the 12S is plugged in unless you turn the fridge off. Also, if your leisure battery runs down, the car battery will equalise with it, charging the leisure battery up a little, but discharging the car battery. Obviously these factors can cause problems when it comes to starting the car, hence the use of a split charging relay to ensure that the power is turned off to the leisure battery and fridge if the car engine is not running. Newer vans have a switch you can use to run the van electrics from the car battery without the need to have the car engine running. This does not charge the battery or power the fridge which should only ever run from the car, and only when the engine is running. The fridge circuit is entirely separate from the leisure battery.
What you say is correct, but I would be concerned about flattening your car battery. Also car batteries are not designed to be deep cycled as a leisure battery, so using it in this way will also reduce the life expectancy of it.
It is not that expensive to do proberly if you do it yourself and you can have peace of mind that you won't have to push the car in the morning. I considered using the fog light to charge a leisure battery in a trailer tent, but decided against it when I realised how much the bits were and how easy it was to do. If you upgrade your caravan then you will end up having to do the job properly anyway. To do as you propose you will need the cable from the battery (don't be tempted to take a feed from the car's wiring in the boot as the fridge will burn the wire out and leave you needing the car rewired if not on fire!) You will still need a 12S socket, and a fuse. The only thing you will not be using is a £10 smartcom relay. It seems a false economy to me not to do it properly. If you are looking to cut corners, you could use the cheaper W200 kit, but that involves more wiring and for the sake of £3.50 doesn't seem worth the hastle.
TBH this really is a temporary fix just for this coming weekend. I think the leisure battery in the van will be fine, I just want the peace of mind of having the cars batteries as backup. They won't be running the fridge (thats on gas) so I really don't think they'll flatten over the weekend (they're Optima deep cycle batteries.)
Thanks for that detailed info LegsDownKettleOn, that makes a lot of sense. i'll buy the socket and the cable and just take them with me so if needs must, I can fix it direct to one of the car batteries. I'll scrub the idea of cooling the fridge on the journey then, i make that a draw of up to 14amps, certainly enough to start a fire as you say!
I'll post back when we return to ask for advice fitting the split relay which sounds the best thing to do so it'll all be done properly for the next, longer trip away.
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Topic: Auxillary wiring
