If your grey plug is wired up correctly then yes it should charge the battery when towing, you should have a relay on the car which amongst other things will switch the charge to the caravan battery once the engine is running & car battery is charged
If I'm towing I can have the fridge running on the 12v setting and I believe it will keep running if I stop. If I stop for some length of time and the battery in the van runs low will the car battery kick in to charge it up? If so is there any sort of system in place to stop the van from draining to much power from the car leaving me with not enough power to start the engine?
Surely, plug in or out, the fridge will not run from the caravan battery? I'm not sure that it can run from the car battery either unless the engine is running. I always thought that the fridge was wired separately from the other 12 volt equipment, as it would quickly flatten a battery.
Both the fridge and the caravan charging circuit should only be supplied when the car is running. With the advanced electronic fitted to cars nowadays, the method of determining how the parameters are met may have changed, but previously the split charge relay would only be energised once the ignition warning light went out. If memory serves, the feed was taken from the low-tension wire on the alternator.
If wired correctly, it wasn`t possible for the caravan charging circuit or fridge to draw any power from the car electrics unless the engine was running and the ignition warning light extinguished.
I believe you are right Juan, both will get a feed through the relay when the car is revving a bit more than tick-over. On modern vans it will never run off the caravan battery because of the possibility of draining it, similarly it won't run off the car battery either for the same reason Therefore only when the alternator has excess current to charge will it do so, ie, whilst travelling to your destination (which in fairness will be most of the time). Set-ups have changed over the years but for trouble free use they have evolved into the above.
Dave.
------------- Never argue with an idiot, they will drag you down to their level and beat you on experience.
Mark Twain.
My car only charges the caravan battery when on the move, and will give the car battery priority when, for instance, the engine is idling. The charge to the caravan is only a "maintaining" one - it will not bring the fridge temperature down, as is the case when on mains electric or gas.
Bertie.
If the engine is not running and the grey plug is plugged in, the caravan 12 volt equipment excluding fridge and battery charging, will work from the car battery not the caravan battery.
Unplugging the grey plug will make it work from the caravan battery.
When plugged in and engine running, battery charges and fridge works and... all the caravan 12 volt equipment excluding fridge and battery charging, is isolated and will not work at all.
Important to understand this because if you have an overnight stop and don't unplug the grey plug you may have a flat car battery in the morning.
Ok. So if I've got this right the fridge will only run on 12v while the van is plugged into the car with the engine running. The fridge will stop working as soon as the engine stops?
I'd assume that as long as the fridge door is shut it will stay cold for a good few hours.
Quote: Originally posted by Daves mate on 27/4/2018
Ok. So if I've got this right the fridge will only run on 12v while the van is plugged into the car with the engine running. The fridge will stop working as soon as the engine stops?
I'd assume that as long as the fridge door is shut it will stay cold for a good few hours.
That is correct. There are two possible scenarios: the old style split charge relay has a power supply taken from an ignition controlled point in the car. The relay only operates once the car voltage reaches a given value, so once the engine is switched off, power to the fridge is cut, thus preventing the car battery from going flat.
Modern cars can still use the old relay, but are better fitted with a dedicated module, that does the same job, but also cuts supplies to the cars brakes lights, fog lights, and reverse lights to avoid glare. Also any rear parking sensors are de activated.
When the 7 or 13 pin plugs are connected, the caravans habitation relay is activated, to cut the operation of 12 equipment , other than the fridge when towing, This to avoid any chance of caravan kit causing interference with the towcars electronics, for safety reasons.
Quote: Originally posted by Daves mate on 27/4/2018
I'd assume that as long as the fridge door is shut it will stay cold for a good few hours.
I would be wary about "a good few hours". When we travel overnight to France the ferry journey is around 8 hours. If we arrive very early at Portsmouth and are going to be on the apron for some time, I switch the fridge to gas for this period. But we do not have anything in the fridge that cannot be re-chilled if it becomes partly defrosted.
A gippy tummy is not a good start to a holiday.
Bertie.
there is one other factor involved about the disconnect unless the engine is running system .. without it given a flat car battery if connected to the van battery the car engine would attempt to start from the van battery.. not a good idea when a few hundred amps are involved and a few yard of relatively thin cable between the two..
as i understand it the "habitation relay" disconnects the van battery from the cars electrical system unless the car engine is running.. mainly for the reason i have just mentioned..
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Topic: Charging the caravan battery whilst towin
