No, I’m not starting an Agony Aunt post..!
A couple of days ago one of Caravan Chronicles readers, Vic, posted in the comments section of “Understanding Caravan and Tow Car Electrics” that he recently flattened his car battery by leaving his caravan connected to his car. Here’s what he posted:
Hi Simon, while travelling across Spain I made an overnight stop and left the caravan connected to the car electrics I also hooked up to mains. The next morning the car battery was flat, I’m sure I’ve done this before with no consequence. All I can think is that european site wiring can be suspect.
brilliant article.
OK, that got me thinking…
Was it the car-off-van switch faulty? Was there another fault of some sort? I asked Vic for the details of his caravan and he replied it was a 2009 Bailey Senator California. I don’t know the exact details for Bailey electrical schematics, but it should not be too difficult to work out what might be happening. I started to think of various failure scenarios that ‘could’ account for Vic’s problem. At this point I have to say I’m indebted to David Rose for sending me information about the electrical services in Bailey Caravans.
Looking closely at the schematic of the control unit, it all hinged around the correct operation of four relays. Here is the schematic I have drawn out in a simplified form:
The drawing (above) shows the four relays – R1, R2a & R2b, R3 as they are set when the caravan is not connected to the vehicle and the master switch is off. The red lines show what part of the circuits are live. The master switch controls relay R1 and when energised by turning the Master Switch on allows current to flow to the caravans 12 volt electrical system via the 12 volt fuse board.
Above: We have now turned the Master Switch on and can see that relay R1 has energised and is allowing current to flow to the caravans 12 volt services. The caravan is not connected to the tow vehicle.
Above: The caravan is now connected to the tow vehicle and the engine is running. The caravan master switch is off. With the fridge circuit powered from the running engine, it energises R3, R2a and R2b. Relay R2b disconnects the master switch circuit so that it cannot operate R1. Relay R2a connects the leisure battery to the 12 volt permanent feed from the tow vehicle. R3 energises, but only switches the feed for the master switch from the leisure battery to the permanent 12 volt supply from the tow vehicle. As this stage it cannot be used to supply the master switch due to R2b being energised.
Above: The caravan is still connected to the tow vehicle, but the engine is off. Relay R2a and R2b that are controlled by the fridge circuit are now not energised and revert to the default position. However as the caravan is still connected to the tow vehicle, the 12 volt permanent feed keeps relay R3 energised, therefore supplying the Master Switch – not from the leisure battery but from the permanent 12 volt feed from the vehicle.
This now leaves us in the following position:
Above: The caravan is connected to the tow vehicle but the engine isn’t running. The master switch is on. The caravan now receives it’s 12 volt feed from the tow vehicle to power all the 12 volt services. I have greyed out the live circuits from the leisure battery. Even though the caravan is plugged into a EHU bollard, the 12 volt services will be run from the vehicle battery and not the mains charger/ leisure battery circuit. The fridge will continue to work on 240 volts as will any mains powered equipment.
So, it’s not a ‘fault’… it’s a ‘feature’ ! Leaving the caravan plugged into the car and turning the Master Switch on allows you to power the caravan’s 12 volt services from the car. Disconnect the lead from the car and the caravan will be powered from the leisure battery.
I hope this solves Vic’s puzzle.
.
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Caravan Chronicles 
Hi Simon.
Thanks again for the valuable information.
The circuit board containing numerous relays was replaced a month ago without any solution.
As requested I have performed tests with a multi meter and advise the following.
Both refrigerator & the Alko anti sway circuits are receiving voltage from the vehicle and earth paths are OK… Refrigerator works OK on Gas 12v & 240v
12v (actually 13.7v) is being received from the vehicle into the caravan refrigerator circuit BUT NOT into the battery which shows 12.5v. If i disconnect the car & connect the caravan to 240v the battery is charged via the onboard battery charger.
The master control panel which has buttons for “MASTER, LIGHTS, PUMP & AWNING is illuminated when the “master button” is pushed.
The “awning button switches the awning light on and off whilst all the other buttons indicate On and Off but nothing happens… hence the initial reaction that there is no 12v in the caravan.Other things that don’t work are (a) no oven and cook top “pizo”ignition (b) no toilet flushing (c) no power to the TV antenna booster (d) no Aldi hot water and therefore no heating (e) no pumping from the caravan water storage tanks.
I have on order Bailey Part #2010113 Master control board in the hope that it might work.
My apologies for this lengthly email.
Regards from an almost Covid-19 free Australia.
Ken Birch
Hi Simon and other Bailey Pamplona (Australia) owners.
Have recently located your posts and are amazed at your insight. My 12v electrics failed completely on a recent ’round Australia trip.Nothing works… no lights, no heating, no hot water no pump to water tanks and no toilet flushing.. Have obtained and replaced the main fuse board containing the relays. I had hoped that there was a faulty “habitation relay” on the fuse board but the replacement doesn’t work either. The “master control board” indicated that these items are functioning but they do not. I have ordered a replacement control board item 2010113 and hope this fixes the problem. . Any thoughts on a solution.
Thank you…
Ken Birch in Australia.
Hi Ken
Sorry to hear of your problems… Bailey tend to be slightly better than some other European brands in the electrics department.
A total failure is rare… not what you want to hear though!
I would check that the caravan is actually getting a 12 volt supply from the vehicle to the fridge circuit… this circuit is also the one that trips the habitation relay. So if you can confirm you have a supply on the leisure battery charging circuit from the vehicle and from the fridge circuit from the vehicle and the earth return paths are good for both circuits (they are separate in the caravan) then as long as you leisure battery is charged it has to be down to the control board and/or relays.
I know Bailey made some tweaks to the electrical system for the Australian market… so I’m not 100% up to speed on them… I’ll see if I can find a wiring diagram of one here in the UK.
Good Afternoon Simon,
When I connect my 12volt leisure battery onto my 2016 Bailey Pursuit caravan, there is a spark on the second clamp I connect which indicates that the battery is being drained. The master switch is OFF, fridge, motor mover, radio, TV amplifier and lights are all OFF, and there is no vehicle supply, solar panel or mains supply connected.
So (I think) there is an electrical fault on the 12volt system.
I cannot find the R1, R2 & R3 relays
Please can you offer advice on how to proceed?
Thank you
Ian MacMillan
Hi Ian
Pretty sure that the alarm fitted to the caravan has an internal battery and small DC to DC charger to keep the alarm’s internal battery topped up. I suspect that this will be the current draw you are seeing. When you connect the leisure battery the alarms internal charger has a relatively high inrush current for a split second then drops down to only a few mA. It might be worth checking on the state of the alarms internal battery. I know on my caravan I’ve had to replace it at about 4 years old, mine was a 12 volt 12Ah sealed lead acid battery.
AH… the Bailey alarm must be a self contained unit, only our smoke and CO2 alarms are powered by 9 volt batteries. The three relays are on a circuit board in the 12 volt power distribution unit, you would have to remove the unit and disassemble. They are not like the normal automotive relays.
Hi Simon,
Thank you again so much for your support,
I believe I only have smoke and CO2 alarms powered by their own PP9s, could I have I another one I am not aware of?
Also is the 12 volt power distribution unit you mention inside the box that the 12volt fuses are fitted to, (which is part of the 240volt mains distribution unit?) I have failed so far to remove the front cover of this unit – as part of the cupboard it is built into has to be removed first which to date I have failed to do as it seems to be jammed between the front beds.
Doesn’t the caravan have a security alarm? I thought it did, if not, then the parasitic drain must be from something else – tracker maybe? If it happens with the master OFF then it must be between the battery and master switch. I would be worth tracing that lead first.
I can’t remember the specifics for your model of caravan, but just follow the 4 leads from the 13 pin socket cable where they enter the caravan to the control unit. The 4 leads should split off from the remains cables going to the road light cabling.
So as I have too understood Bailey caravans are wired up by complete idiots. I am a boat person and Australian army. This system is BS and I emphasized the bull!
To design a system to kill the start battery over the house battery can only be designed by a moron. Oh that’s bailey:) yes I have found so many issues with there systems including several breaches of ADR it’s funny. Every time I question them they either don’t answer or fob it off. Sorry exposed gas lines to road rock damage, no fuse on battery for over 1000mm of wiring (plus a few plugs) until it gets to the psu (this is a void insurance one for everyone)
The van is a 2013 bailey unicorn Pamplona. Not a cheap one. I wish everyone to stop asking caravan sale people who have zero idea, if you have a problem or want to design something talk to a business at person. On a boat if things go south it’s really bad, caravan people go “oh well, I will try and fix it but no guarantees” on a boat… your dead. So who will you ask for help?
Hi Simon
Don’t think we’ll be off electrics often enough to warrant anything too complicated. I just felt that if I could use the car battery whenever we’re at the van then the leisure battery would last much longer. Not even worried about running the car to charge the battery. So I’d just want to connect the relevant pins with the extension cable so that the van recognised and used the car battery. Would my original cable suggestion work for this purpose – presumably just the one pin 13 earth would be adequate if not charging through the cable.
Hi Keith
Yes, your cable would work 🙂
Hi Simon
Can I add my appreciation for the clarity of your explanations on this website?
This particular thread is most useful as we have made the odd overnight stop while touring abroad where disconnection has not been necessary. Seemingly our 12V useage is not as high as Vic’s!
Incidentally we tow a 2014 Bailey Unicorn.
This got me thinking. In the old days, some 35 years ago, when on site in Spain with no EHU I used to connect the caravan to the car battery for limited 12V use overnight and rely on the car battery recharging on journeys out and about during the day. It seems that I can still extend my leisure battery use when off electrics by connecting the car but this would be quite inconvenient – backing up and parking within range of the A-bracket.
Could I make up an extension cable with 13-pin connections using just two of the pins – presumably 9 and 13? There would presumably be some limitation on the length of the cable – I was thinking about 10 feet would allow parallel parking nose to tail.
Hi Keith
I have made myself a lead from 4 core 4mm2 cable (the cable was originally designed for 3 phase mains equipment) with a 13 pin plug on one end and 13 pin socket on the other. It’s about 3 metres long and use this to connect the vehicle to the caravan. As I have the Sterling Power Wildside unit installed (DC to DC Charging) with the vehicle on tick-over I can put around 24 amps back into the caravan battery (measured at the battery terminals). Don’t forget you MUST use BOTH earth leads for the lead – only one earth connection in the lead will be overloaded!
Hi simon,
In my eyes, you should be well credited for solving this mystery, it has taken a lot of time and effort posting the home-made customised diagrams etc, I don’t know of anyone else who would go to the lengths and efforts to find answers to these sort of mysteries. Behind the scenes, I have a feeling that some caravan manufactures read your posts within your site and pick your brains, well, looking at the above scenario, they certainly appear not to know it all.
Hi Snowy
I have had a few ‘issues’ emailed to me from manufacturers/suppliers asking for my input. I have in the past emailed them back, and received no credit. Now I will only answer technical questions if they are posted in the blog.
It’s the same when manufacturers have contacted me about reviewing a bit of kit… I tend to email them back with all sorts of technical/difficult questions… and suddenly they disappear. That’s why there are very few reviews. I’ll ask awkward questions and tell the truth about a product.
sorry, I’ve made a slight mistake; i.e. One of the aims of R3 is to isolate the charger/ traisformer from the drawing vehicle should the caravan be connected at the same time as the mains, the relay should also be wired to act as an automatic, van-off-car, seletor switch. The said relay cuold be wired to undertake these functions with a few wiring alterations & diodes.
snowy
HI Simon,
Very Very interesting, upon following the shown diagrams I totally agree with your conclusions.
In my opinion, it’s an oversight by the manufactures not undertaking their in-house homework upon designing the on-board electrical systen.
The purpose of relay three (R3) ;
Correct me if I’m wrong, but I understand that there was a change sometime ago within the caravan safety regulations regarding the isolation of mains operated appliances within caravans becoming in contact with the drawing vehicles’ circuitry if the mains 240v was connected whilst the towcar was connected.
The function of relay three (R3) is to disconnect the mains battery charger/mains transformed 12v power supply from being connected to the tow-cars’ circuitry while the vehicle is still electarically connected.
In this case, the wiring of R3 is totally incorrect in my opinion as you correctly say Simon, if the tow-car is left connected, the caravan domestic 12v services are running off the tow-cars’ battery.
To add to this, the said relay is NOT isolating the mains charger/transformer from being able to connect to the drawing vehicles’ circuitry after the tow-cars engine has been started. If you look at the relays, as you correctly say; R3, R2a & R2b are energised but the charger/transformer is still allowed to connect to the drawing vehicle as it is connected in parallel with the caravans’ leisure battery even though R3 has supposedly isolated it to conform with the supposed change in regulations.
I say no more, I rest my case.
Snowy
Hi Simon, Thank you for a most informative article, explained in plain English. Great website, keep going please.
Cliff
Hi Simon
thanks for your time and effort in solving the problem.
Regards and many thanks
Vic
I take it there’s no car/off/’van switch fitted to the caravan then ……??
Hi Andy
No, the caravan post dates the old ‘car-off-van’ switch. I’m not sure when this would have been dropped from the Bailey range of caravans.
S