I just bought an older caravan. A lunar Carina with two seven pin connectors. A very solid caravan. Problem is my tow vehicle has a smart alternator. I would like some advice on how to wire the dc-dc charger to keep the house battery charged and how will it work in keeping the fridge running while driving.
TIA
We have an older caravan too, and our fridge only works on mains electricity. What we usually do is cool the fridge down overnight before we go away by plugging the caravan into the house mains, then pack some of the food that we want to take with us. In the meantime we put a few ice packs into the freezer at home. Just before we set off we load up the last few things in the caravan fridge along with the ice packs. When we get to the site the fridge is usually still well cold. The ice packs are usually at least partially frozen. As for the battery, that will have been charged at home by the house mains overnight.
I must admit though we only ever go to sites with EHU, so we plug in as soon as get there. We no longer go off-grid as that would mean we had no fridge and no hot water.
I can't help with the smart alternator though as I've never had a car with one. Our tow car is nearly 17 years old too. (The caravan's nearly 33!)
Although I've never bothered to look at the details, my car is Euro 6 rated which means it almost certainly has a smart alternator, and the way the battery charges rather confirms that.
I had my towbar/electrics as a factory fit option, and it appears to be fully integrated into car 'computer' systems, with changes to what functions and in operating characteristics when a trailer is attached (powered tailgate, lane control disabled etc.).
Without any additional mods to towbar electrics, they power my caravan fridge, leisure battery charger, and ATC perfectly well. Never needed to put on lights to get 'power' out of the towbar electrics.
Now, that's my car, can't vouch for others doing the same. My towbars electrics are 'trailer attached' sensing, which triggers a LOT of things, all of the outputs on the socket pins are zero if simply measured with a meter, but once trailer plug connected, all works normally. Now it could be that part of the system changes initiated by attaching a trailer are to power the 12v outputs sympathetic to the trailer needs, effectively modifying the 'smart' behaviour of the alternator. If so, that may not be the same with all vehicles!
End of the day, my 'smart' alternator powers the caravan just the same as a 'dumb' alternator would. Worth trying yours before spending money on additional DC-DC chargers that may not be necessary.
If you do need to go down the DC-DC charger route, ensure it's powerful enough, fridge and leisure battery charger can easily put a 20A or more load on the supply!
Have you ran separate positive and negative wires from the tow vehicle all the way back to the caravan battery through the dc-dc charger?
I was thinking there should be a way to tap into whatever wire runs off the towbar wiring that goes into the caravan and run those wires through the dc-dc charger.
Quote: Originally posted by Monty15 on 23/12/2024
Although I've never bothered to look at the details, my car is Euro 6 rated which means it almost certainly has a smart alternator, and the way the battery charges rather confirms that.
I had my towbar/electrics as a factory fit option, and it appears to be fully integrated into car 'computer' systems, with changes to what functions and in operating characteristics when a trailer is attached (powered tailgate, lane control disabled etc.).
Without any additional mods to towbar electrics, they power my caravan fridge, leisure battery charger, and ATC perfectly well. Never needed to put on lights to get 'power' out of the towbar electrics.
Now, that's my car, can't vouch for others doing the same. My towbars electrics are 'trailer attached' sensing, which triggers a LOT of things, all of the outputs on the socket pins are zero if simply measured with a meter, but once trailer plug connected, all works normally. Now it could be that part of the system changes initiated by attaching a trailer are to power the 12v outputs sympathetic to the trailer needs, effectively modifying the 'smart' behaviour of the alternator. If so, that may not be the same with all vehicles!
End of the day, my 'smart' alternator powers the caravan just the same as a 'dumb' alternator would. Worth trying yours before spending money on additional DC-DC chargers that may not be necessary.
If you do need to go down the DC-DC charger route, ensure it's powerful enough, fridge and leisure battery charger can easily put a 20A or more load on the supply!
Thanks for that. I already have the dc-dc charger from a campervan. My towbar was just installed last week but I rather doubt the wiring is an integrated system. I will find out shortly.
Quote: Originally posted by Colin21 on 22/12/2024
We have an older caravan too, and our fridge only works on mains electricity. What we usually do is cool the fridge down overnight before we go away by plugging the caravan into the house mains, then pack some of the food that we want to take with us. In the meantime we put a few ice packs into the freezer at home. Just before we set off we load up the last few things in the caravan fridge along with the ice packs. When we get to the site the fridge is usually still well cold. The ice packs are usually at least partially frozen. As for the battery, that will have been charged at home by the house mains overnight.
I must admit though we only ever go to sites with EHU, so we plug in as soon as get there. We no longer go off-grid as that would mean we had no fridge and no hot water.
I can't help with the smart alternator though as I've never had a car with one. Our tow car is nearly 17 years old too. (The caravan's nearly 33!)
Thanks for that. I will try the dc to dc charger route and failing that do as you do.
Another solution is to have a relay fitted so that the caravan has a constant 12v supply direct from the battery. When the engine is not running the relay shuts down the 12v feed so the battery does nto go flat.
the problem is the long length of cable between car and caravan.. this causes a voltage drop meaning the van battery never gets a proper charge..
a 20 amp dc to dc charger take whatever voltage gets to it from the car battery and boost it to 20 amps.. i have mine on a manual switch but normally they are automatic and only come on when the engine is running..
Quote: Originally posted by birder99 on 25/12/2024
Use a separate connection from your existing towing connector, something like an Anderson connector will take 20A
I was trying to figure out how to run a wire from the existing connector where it enters the inside of the caravan then to the dc-dc charger then to the battery.
I was trying to figure out how to run a wire from the existing connector where it enters the inside of the caravan and then to the dc-dc charger then to the battery. I just don't know which wire would be the one that is used for charging the battery in the caravan. I will figure it out eventually.
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Topic: Dc to dc charger
via mobile 22/12/2024 at 2:10am
