Hello to everyone out there,
Just came across a bit of an oddity on our 2006 Elddis Knightsbridge (Avante clone) which we purchased earlier this year.
We have used it quite a bit over the time we have had it but never realised until yesterday that the on board battery is not recharged whilst towing. The thing that gave the game away was using the motor mover to put the van on the hitch at our last site.
Now on our previous van, also an Elddis but a 1998 Jetstream, we would arrive home from the same site and on taking the battery home find it was almost fully charged, needing less than one hour to bring it up to fully charged. This time the battery tok some four hours to fully charge.
An inspection of the owners handbook showed no connection to the split charge circuit on the car, although the 12 volt fridge feed was present.
Not believing the book I took the covers off the 12 volt system and using a multimeter proved that this was indeed the case.
So now I have had to design and build a suitable circuit to get round the problem.
Does anyone else have a similar experience? Because if we had been going to a non hook up site we would have arrived with only a partially charged battery.
Very strange!
so you have been on ehu and still your battery didnt get any charge? that suggests to me that your issue is one of the charger not working at all, nevermind whilst your towing. what is your battery reading?
you need a DC to DC charger to properly charge a van battery..
i have a renogy 20 amp one.. this basically takes voltage (whatever it gets) from the cars battery and boosts to put a controlled 20 amps into the vans battery..
You need to check the towing socket with a multimeter when the engine is running to see if you have a live feed from the vehicle alternator or not. If it's a 13 pin towing socket then the pins to check are 9 & 13 which 9 is the battery supply and 13 is the earth for pin 9. If you Google '13 pin trailer plug wiring diagram' you will find various diagrams to find out which are pins 9 & 13.
the real problem is the voltage drop between the cars alternator and the vans battery.. the cable run is too long and there is never enough voltage left to properly charge the vans battery..
another problem is modern cars have smart alternators this is for economy reasons but it also stops a caravans battery from being properly charged..
I can't comment on smart alternators as I know nothing about them, but wouldn't have thought there would be any problem with an "ordinary" alternator.
Many years ago I made my own split charging system, before I had even heard of such things, for my Mk2 Cortina and Sprite caravan. The Cortina had a dynamo at first too until I changed it for an alternator. It worked fine even with the dynamo, and in fact it was the only way the caravan battery got charged away from home, as few sites had EHU then and our caravan had no facilities for it anyway. I did use fairly hefty cable though.
Re. Trogg message.
I bought a new BMW last year, previously with factory fitted tow bars they left out 2 pins i.e. charging and fridge but mine had the 13 pins. Just to make sure I checked out the relevant pins in the 13 pin socket and with the engine running there wasn't any voltage reading. I got in touch with a mobile auto electrician, he came out and connected his box of tricks. With the engine running there was no voltage reading but he then asked me to switch on the headlights and straight away there was voltage (I can't remember what the reading was). He said that is what happens with smart alternator, and advised me to keep the headlights on whenever I am towing to overcome this problem.
smart alternator or not the long cable length between a cars alternator and the van battery means there is never a high enough voltage reaching the vans battery to fully charge it..
a DC to DC charger remedies this.. mine is a 20 amp version but you can get bigger ones.. bigger ones do require a hefty cable running from the cars battery..
if plugged into the mains all the time none of this matters but if you want to get some real use out of the vans battery it does..
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Topic: Charging caravan battery whilst towing.
