12 S electrics

[gordon_374330937]

I have a 12s extension lead for using on long stays where the caravan battery runs low, to draw power from the car. The 12S from the car is wired pin 4 permanent live. The caravan is a Lunar Chateau 2006 and has no system for manual switching inside the caravan. When the car ignition is off I have pin 4 on the 12s giving permanent live but if i take the caravan battery out of the system, the caravan internal lights do not work, does this mean I cannot power the caravan internal lights from the 12 S socket?

 

[antrimboy]

I would have expected your internal lights to work ok. Are you sure that you have a live feed on pin 4, and also that pin 3 has a good contact on the car?

 

[BigAl1]

Gordon

What happens if you plug the car to van without your extension lead?

Maybe there is an excessive voltage drop through the extended cables.

You say that your extension has pin 4 (Green) permanantly connected to live but is pin 3 (white) also connected in your extension?

Al

 

[rayc]

gordon, I suspect that there is no connection in the caravan from pin 4 of the 12S to the internal 12v system.

You say that there is no manual, ( and I suspect automatic ), switching in the caravan to switch between the van battery and the permanent feed. The internal electrics can only be fed from the battery. That in a nutshell is your problem.

It would be a fairly simple wiring job to sort it out so that it will work as you wish.

 

[rayc]

gordon, I suspect that there is no connection in the caravan from pin 4 of the 12S to the internal 12v system.

You say that there is no manual, ( and I suspect automatic ), switching in the caravan to switch between the van battery and the permanent feed. The internal electrics can only be fed from the battery. That in a nutshell is your problem.

It would be a fairly simple wiring job to sort it out so that it will work as you wish.

Gordon , as Al has said do you have the supply between pins 4 & 3 [i.e. positive on pin 4 negative on pin 3]?

 

[JTQ]

My 2002 Hymer is just the same; I can't power the 12 volt systems directly from the car even though that has an always live supply. I believe this is because all the 12 volt services from the battery are taken via the "Controller", and that specifically isolates them from the car. A pain for CL type use but seemingly a deliberate design feature. I also read that the supply is taken via the Controller as it features low voltage protection to save the battery from over discharge damage. So rewiring to avoid this might not be a sensible route.

 

[rayc]

JTQ, It should still be easy to rewire so that it is possible to power the internal 12v from either the internal battery or the permanent feed and still keep the van battery connected via the "controller" if you wish. All the controller is doing is disconnecting the battery at the Drop Dead Voltage which is normally 10.8v

It amazes me what is specified these days. I rallied on non electric field sites for 20 years and fed the electrics from the van battery or the car without any problems. It was the way things were done and thousands of caravanners did the same. The lights go dim, the water pump slows down or the TV stops working and you recharge the battery. We didn't worry about drop dead voltages etc. We bought the largest / cheapest car batteries from the local scrap yard and they carried on working for years.

Still that's progress.

 

[gordon_374330937]

Thanks

 

[gordon_374330937]

gordon, I suspect that there is no connection in the caravan from pin 4 of the 12S to the internal 12v system.

You say that there is no manual, ( and I suspect automatic ), switching in the caravan to switch between the van battery and the permanent feed. The internal electrics can only be fed from the battery. That in a nutshell is your problem.

It would be a fairly simple wiring job to sort it out so that it will work as you wish.

Ray,

 

[gordon_374330937]

gordon, I suspect that there is no connection in the caravan from pin 4 of the 12S to the internal 12v system.

You say that there is no manual, ( and I suspect automatic ), switching in the caravan to switch between the van battery and the permanent feed. The internal electrics can only be fed from the battery. That in a nutshell is your problem.

It would be a fairly simple wiring job to sort it out so that it will work as you wish.

Ray,

Thanks, yes I hace checked out pin 3 & 4 on the 12S. I think you are correct its a feature of the electrical/charging system of the caravan. The internal lights are wired only to work of the caravan battery. If I connect the 12S permanent live to the pin that charges the caravan battery presumably the car and the caravan battery would equal themselves out?? This could be a solution for me as long as I kepy an eye on the car battery voltage? Open for suggestions!

Gordon

 

[JTQ]

Ray, yes I agree it is possible to wire up something.Possibly a double pole change over switch.

The discussion takes me back to the days of the excellent welsh made "Unicharger" which enabled you to recharge the vans battery from the car each time you came back to site after a day out. Brilliant device, lifted the voltage from the car to effect a steady charge, and monitored the cars battery to ensure it retained enough to start it in the morning. Pity they ceased trading many years ago.

 

[rayc]

Gordon, I have copied your comment herte so I do not get confused:-

"Thanks, yes I hace checked out pin 3 & 4 on the 12S. I think you are correct its a feature of the electrical/charging system of the caravan. The internal lights are wired only to work of the caravan battery. If I connect the 12S permanent live to the pin that charges the caravan battery presumably the car and the caravan battery would equal themselves out?? This could be a solution for me as long as I kepy an eye on the car battery voltage? Open for suggestions!"

Gordon

If it were me I would get a 3 pole switch with a common centre pole, which can be switched to either of two other poles when switched in either direction. It should be rated at 20A DC and should be available at any car accessory shop.

Locate the cable that feeds the light circuits from your control box, disconnect it and connect it to the centre common pole. Connect one of the other poles to the terminal that the lights supply was connected to and the other to Pin 4 of the 12S.

Ensure that the white wire in the 12S ( pin 3) is connected to the van battery negative [ it may already be connected somewhere].

In one direction of the switch the lights will be connected to the van battery and in the other they will be connected to pin 4.

Ray