Caravan hook up charger

Get more free help and advice when you join the Club. Good connections are important to maximise current flow and allow the charger to sense the battery. Removing your leisure battery and periodically and charging it with a good leisure-battery charger will help keep it in tip top condition. The important thing with any rechargeable battery is to know when to recharge it, how fast to do so and for how long.

Most leisure batteries use lead acid technology very similar to that used for car batteries. In time we may see the emergence of lithium-based batteries for this role but they are beyond the scope of this Data Sheet. It is also worth noting that lead acid batteries discharge through internal leakage, even when no load is applied. Some types are more resistant than others to this phenomenon but, as a rule of thumb, batteries in storage and not in circuit should be charged every three months or so.

A lead acid battery will not perform well if it is completely discharged. Some types of lead acid battery notably gel types stand up better than others to this type of treatment but, as a rule of thumb, 50 per cent should be seen as the maximum level of discharge before recharging. Pin 9 is for charging the leisure battery and should be live permanently connected to the tow vehicles battery via a 15 amp fuse.

From the sounds of it, I would guess that the previous owner did not use the fridge while towing therefore pin 10 was never connected. The relay fitted in your tow vehicle, is it a true split charge relay i. I assume the split charge relay in your vehicle goes to Pin 10 fridge from what you have said. With that done, if it is a voltage sensing relay in the car, I personally would swop it for a standard 30 amp relay operated from the ign contact on the alternator, or if your vehicle has it, the correct contact on the ECU.

Voltage sensing relays unless set perfectly can switch off when the voltage drops in the vehicle because you turn on the heated rear window, headlights etc. Some have a habit of cycling on and off… they switch off because the caravan load drops the voltage…. July 31, at The relay on the car is a voltage sensing relay.

Caravan dc dc charger - vehicle anderson plug install

When I bought the caravan and saw that it had a 13 pin plug I got a local workshop to upgrade the towing electrics from the 7 pin socket that was fitted on the car to a 13 pin one. They recommended a voltage sensing relay and gave me the documentation. It connects at It can pass A of current, continuously and A for short periods. I started the car, and did not touch the accelerator. Thanks to your excellent help page I realise now that a split charge relay is an old fashioned concept that is not necessary on a modern towcar, but I will stick with the current relay for now.

My next car will be equipped with a simple relay. The caravan is a Caravelair from , the wiring appears to be original. The 12 V side is extremely simple. The leisure battery in the caravan is also connected to everything including the fridge. All in all a recipe for a flat car battery. It is a device fitted beside the caravan battery that takes the current received from the car and transforms it up to Thanks for your advice. With that current rating I wonder if it is one of the solid state units? The only one I know about is made by Sterling Power, but it is something that I have been pondering on for a while.

I think C-TEC may make one, and if their chargers are anything to go by, it should be a good product. July 31, at 9: I have bought a 30 A changeover relay normally used in car lighting circuits to use as the habitation relay. I live in Norway. Caravanners who have installed it speak warmly of it.

There is some info here in Swedish: It will boost incoming current to A safety feature claimed by users but not by the manufacturers is that by limiting the current charging the leisure battery, cables between the cars alternator will never be overloaded if the leisure battery is very low and draws a high current. When rewirering my caravan I am going to install fuses. I got an english translation on the web site, but I could not find a manual for it.

Will have a look via Google. If you apply say If you want to increase the current, the only way to do it is increase the charging voltage across the battery, Thats how some intelligent chargers can recharge as battery quickly, they step charge by changing the voltage in steps.

Obviously as the state of charge, hence the chemistry changes, the internal resistance changes too. So this bit of kit will charge at August 1, at 4: Hi Simon, The booster is installed in the caravan, as close to the leisure battery as possible to keep the length of the cables as short as you can. I am considering replacing the battery charger in the caravan. The present one is not automatic, and I keep forgetting to switch it on, or sometimes switch it on the wrong setting eg. The caravan has a V — 12 V transformer, so I only need a purpose built battery charger.

One charges at 6 A, the other at 30 A. They are attractive for caravan use as they are fully automatic and have no fan for silent operation. I feel that the 6 A will suffice, but do you feel that a 30 A charger is a better buy? Most of the current caravans seem to have a 12 volt charger around the 15 to 20 amp range, but these are also able to supply the van if there is no leisure battery fitted.

I would think that a 6 Amp would be OK as it will only be charging the battery, not having to supply the caravan without a battery. There may be times when you are using more than 6 Amps in the van during the evening, but the charger then has overnight to replace what was used. Additionally, you are going to always get a good charge while towing. August 8, at 8: The caravan has now taken a step into the 21st century.

I followed your wiring diagrams and the fridge switches off when the car does, and the habitation relay disconnects the caravan battery when the cars engine is not running. The original factory wiring was even stranger than I had supposed. The 13 pin plug was connected to the caravan by an 8 core cable. Pin 3 was the earth for the entire caravan, road lights as well as the internal electrics , and fridge. When fitting new cable I replaced the plug with a new 13 pin one from Nembers. A previous owner had messed with the original plug, removing the locking threads and the bit on the top that locks to the socket flap.

August 8, at It sounds like you are moving forward at quite a speed! So glad the wiring diagrams came in useful. If you know anyone with a caravan that has an interest and wants to learn more… pass on a link to the page. August 18, at 7: I am reading all this info hoping I get a solution to my problem. I switch the fridge to battery, but as soon as I do this I hear a relay clicking on and off at the front of the caravan. The lights flash on and off with the relay. This only happens when fridge is switched to battery. Have you ever heard of this happening before?

Also an I meant to select car battery on the caravan control panel or will the fridge find the 12v from the car automatically? August 18, at The clicking in the caravan is probably the habitation relay, this is actually a switch that is turned on and off by the electrical supply to the fridge, so the clicking is actually a result of the fridge supply being turned on and off. If the fridge supply is being turned on and off, that is controlled by another relay in the tow vehicle. Voltage sensitive relays can cycle….. This is usually because a load is turned on… for example turn on the heated rear window and the voltage drops enough to turn the voltage sensitive relay off.

As it is cycling on and off, its highly unlikely that the fridge is faulty as it would have blown a fuse if it had gone short circuit. Most have a way of adjusting the sensitivity i. If you try to fault find on the vehicle, it might be worth checking to see if you can hear a relay clicking in the rear of the car with the engine ticking over.

You might have to remove an interior panel to find the relay. You could try leaving the caravan connected with the vehicle engine running for 15 minutes and see if it still happens to test this one out. As ever, it is always worth checking the earth connections for the 12N and 12S within the vehicle as over time they can get some light corrosion and need cleaning.

Now there is one more thing to throw into the mix. These alternators measure the vehicle battery charge and to prolong the life of the battery and save energy reduce their output voltage. October 8, at 9: Thank you for writing such a comprehensive article. I do have one question, though. Your article recommends 2.

I believe the 12v wiring on the caravan side is 4mm, having spoken to the caravan manufacture on a different matter. October 8, at Hi Mike The standard 13 core cable for a 13 pin plug on a caravan uses 2. My Freelander factory fitted electrics are 2. A leisure battery can take around 15 Amps via the charging circuit, although it is usually lower due to voltage drop and internal forward resistance. Thanks for your swift reply. I guess we should look at using a 30A fuse inline on that circuit, though, rather than a 15A or even 20A?

October 9, at 7: When you plug in the 13 pin plug to the car, the engine is not running, therefore the fridge circuit is not energised. Only when you start the engine does the fridge circuit become energised, therefore operating the habitation relay and allowing the leisure battery to be charged. This is another reason why you should never connect up electrically caravan and tow vehicle with the engine running. I would not increase the fuse rating above the carrying capacity of the cable.

December 6, at 9: Hi Simon, I would just like to say how heplful your instructions and comments are. December 6, at Fitting a tow bar is not that complex. Post back and let us know how you got on or if you have any problems! December 9, at The habitation relay in the caravan is controlled by the fridge circuit. A voltage sensing relay such as the Ryder one you quoted will allow the vehicle battery to charge and when the voltage rises to a pre set value, the voltage sensing relay activates and allows power to the fridge circuit and in turn switched over the habitation relay allowing the leisure battery to charge.

However, if the ECU detects the vehicles battery is nearing its full charge, it can reduce the output of the alternator before the voltage sensing relay has turned on and therefore the fridge circuit never activates and hence the habitation relay never changes over. One of the easiest ways to check if the ECU has a specific output is to check the electrical wiring instructions that are supplied with a Ford factory wiring kit for 13 pin towing electrics. Usually the wiring diagram will have a lead from the coil side of a ordinary 30 amp relay going to a specific terminal on the main vehicle fuse board.

Land Rovers since are like this. December 10, at 1: Now have I got this right now please advise. December 10, at 2: December 10, at 5: I was just happy to understand the diagram glad you explained that it all makes much more sense now I will let you know when I have completed the job, thank you again. February 3, at Thanks for taking the time to write this article — it was most helpful.

I also intend to connect a mains charger to the leisure battery. My question is should I have some sort of relay that disconnects the charger while the engine is running or if it is not mains powered?

Understanding the Leisure Battery Charging Circuit | Caravan Chronicles

Or will it be ok left in circuit all the time? Difficult one to answer as all chargers are slightly different. By installing a relay that is controlled by the ignition light on the alternator, when the engine is running, the relay will switch over disconnecting the charger from the leisure battery, stop the engine and the charger will be re-connected again.

This also might be safer. February 9, at 7: Thank you so much for your reply. If I could steal a little more of your time and borrow a snippet of your wisdom could I ask you to recommend a relay to do as you suggest. February 10, at 4: Any automotive 20 amp changeover relay is OK. I would suggest buying a relay socket for it to plug into, it makes wiring a lot easier and if there is a problem in the future, its easy to change the relay.

There are other suppliers of course. I would suggest a small investment in a good ratchet crimping tool and insulated crimp terminations, it will allow you to do a top quality installation. Absolutely no reason to apologise. Thank you for getting back to me at all and with such a complete reply. This should be enough to see me through. March 9, at 5: We have a Abbey GTS and have had it connected to the mains throughout the winter.

The display unit shows the battery has The charger switch has been constantly on and the battery was new last April. Please can you advise. March 9, at 6: The reason you get So if it indicates The next check should be to confirm that the battery fuse is OK. Usually it is rated at 20, 25 or 30 Amps. Locate the main battery fuse and check to see if that is OK. March 16, at I have a Kia Sorento which I purchased 2nd hand which was already fitted with a tow bar and 12n and 12s sockets. I found a company that supplied a metal wireless reversing camera which had good heat resisting properties and could be used for continual viewing whilst driving and not just for reversing.

On further checks with a multimeter I found that the fridge 12v system also did not receive any current with or without the engine running. On further investigation of the car electrics it would appear that the system is running from a single supply from the battery via a 15amp fuse without any relays that are obvious, unless they are located to the rear of the vehicle. On renewing the fuse the power was restored to the towing sockets and the caravan.

However, pins 9 and 10 become live whether the ignition is on or not. Seeing your write up on all the safety aspects, is my system operating correctly? Have you any views please. Within the tow vehicle, there should be two supplies running from the battery, a permanent supply for pin 9 fitted with a 15 or 20 Amp fuse and the second supply to pin 10 grey fed via either a 30 Amp relay or voltage sensing relay. This should also have a 15 or 20 Amp fuse depending on cable size. With the ignition turned off only pin 9 should be live.

Pin 10 should only be live with the engine running. Once installed all they have to do is then run the feed wires to the front of the car and connect via a fuse. Voltage sensing relays should ideally always be installed close to the battery for correct operation. It might be worth checking to see if there is a relay of some sort installed behind the panels in the load area of the tow vehicle.

Not all voltage sensing relays are adjustable though. It could also be worth searching on the internet to find the instructions for the factory OEM trailer wiring kit. It might shed some light on the current set-up. Personally with the fault of both pins being live with or without the engine running and the setup having previously blown the fuse I would come down on the side of caution not use the vehicle for towing until the condition of the current wiring is established and the fault rectified. March 16, at 3: Many thanks for a prompt reply.

I think your suspicions are the same as mine and the blown fuse is a bit of a giveaway. It had a 15amp fuse in it and I replaced it with a 20amp, perhaps not a very good idea. I think it will be worth it in the end. March 18, at 4: Hi Simon, I have fitted a vehicle specific wiring kit to my Rave4 with a voltage controlled relay that switches about The problem is when stopped with engine running if I have headlights on the voltage drops below Is there a voltage controlled relay that is adjustable to say Can you help please,Mike. March 18, at 5: Pin 9 should be permanently powered and the Al-KO ATC system should be connected to this pin within the caravan before the habitation relay.

Pin 10 which is the fridge circuit is the one controlled by the relay ordinary or voltage sensing and if it drops out due to low voltage in the tow vehicle, it should not affect pin 9 or the Al-KO ATC. If the wiring kit is an OEM vehicle specific one, is it actually a voltage sensing relay or just an ordinary relay? However if it is a voltage sensing relay, then replacing it with an adjustable one will require it setting so low that it will be on most of the time. It would be cheaper to just use a plain 30 Amp relay and link it to the vehicles ignition circuit. However a good quality adjustable voltage sensing relay can be obtained I think from Sterling Power http: March 18, at 6: Thanks Simon,It is a voltage sensing relay with the kit.

Toyota tell me that there is no provision in the vehicle for an ignition controlled supply so as not to void the warranty on the car I am going to re-route the feed for the ATC in the caravan direct through a fuse to the supply on pin no 9. Thanks for your help,Mike. April 30, at I have an Ace Aristocrat It has two relays in the van. What does this relay do? Replacing the relay and everything should work as normal.

July 17, at 7: Hi Simon Wonder if you could point me in the right direction with this issue. I have a Sterling Sprite excel and suddenly I have no lights all 12v. I checked all fuses and there is no separate light master switch. The battery does not seem to have an inline fuse.

Whichever combination of positions I have used does not power the lights but one combination blows a 20amp fuse. July 18, at 6: The terminals numbered 86 and 85 are the coil side of the relay, put a voltage across these and the relay will switch over. Terminals 87, 87a and 30 are the switch side of the relay. With the relay energised contact 30 and 87 will make the circuit. Sargent have diagrams going back to here: You need to get the habitation relay back correctly then continue testing.

Then check each fuse position to make sure there is a voltage on one side before replacing the fuse and continuing to check the voltage on each circuit. July 18, at Hi Simon Really appreciate your help. Mine is a 96 d so the wiring examples are far more complex. Still confused though as I can trace the battery leads to where it enters the wiring loom and there is no inline fuse.

There is also one other brown red not powered. So I presumed this to go onto 30 after looking at this http: Something else I noticed is that at the time we discovered we had no lights I noticed the pump light flickering and this was due to the water heater air intake having been left open after disinfecting the water system. This caused the pump to nearly empty a full barrel of water and discharge the battery. On ehu for a week did not recharge the battery but strangely when on a trickle charger it showed full in about an hour. July 18, at 1: July 21, at Checked with a meter and the only live fuse was the 20amp basically this was live at the relay.

Also noticed I have live at the grey connection accessory plug.

While following wiring under the wardrobe I had a fortunate discovery as trapped behind the void to the washroom was the caravans manual. And this had a diagram of the wiring which was helpful. I noticed on the diagram even though the relay was not detailed that the lighting circuit went through the relay so decided to put the live on 87a which makes a connection to 30 when the coil is not energised.

Bingo I had all 12v working. So to be clear the relay is now wired 85 earth, 86 trigger, live 87a. I have been trying to find a circuit diagram for your caravan on line over the weekend without much success. One of the possible reasons it is not straight forward is the wiring standards for caravan changed in 98, so your 96 caravan would pre-date the change and I have a feeling it might have been converted over to the post 98 spec at some point.

On most relays terminal 85 and terminal 86 are the energising coil contacts. Terminal 30 is the common, terminal 87a is connected to the common 30 when the relay is not energised and terminal 87 connects to terminal 30 when energised disconnecting terminal 87a at the same time. From what you say I think you have it right, but would it be possible for you to email me a copy of the circuit diagram and I can check to make sure.

July 21, at 2: Will do Simon and thanks. If you can get a clear copy of the wiring diagram, I should be able to draw the correct operation of the relay with the caravan on EHU and with it connected to the vehicle which hopefully will make it easier to confirm the connections. You guys were excellent at helping me get my head around the charging circuit before so I figured this would be the no1 place to come for my current issue.

All has been fine until last week on a trip to Fakenham. All was reset ok and not investigated until the following morning. I checked the 5A fuse on the water heater switch. Fuse was ok and the water heater was functioning perfectly ok on gas. It seems that whatever caused the trip in the middle of the night may have taken out the leisure battery charger which is incorporated in the consumer unit and the electric water heater. Is this feasible and has anyone else experienced a similar scenario? My gut feeling is that the water heater element developed a fault which caused a surge on the circuit and took out the front end of the battery charger.

Is there anything else worth checking fuse wise etc in the charger or am I looking at having to find a replacement water heater element and leisure battery charger?


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The trip that dropped out, was it an MCB for an individual circuit or was it the ELCB that switches all the volt power to the caravan? I would have thought it would be highly unlikely that the water heating element would have caused damage to the charger. That said, heating elements are usually fairly reliable and robust. The 15 Amp blade fuse will be for the 12 volt output of the charger…. On some caravans the battery charger is connected to the mains via a 3 pin euro-plug into the back of the unit… I believe this can come loose and sometimes causes issues when it makes intermittent contact. Also some chargers have on the side or back have a separate fuse holder..

August 9, at Many thanks for your swift reply. I shall check the electrical circuits in more detail with a multi-meter etc like you say. The MCB which tripped had the mains lighting circuit on it as well, so if there was a fault with the MCB, I should have imagined none of that would be working. This would be worth a check too. February 23, at Will it be okay to connect a free standing solar panel directly to the caravan battery as and when I need too? You need to check that the free standing solar panel has blocking diodes to stop the battery discharging in shade and the maximum wattage for a panel without a regulator is only around 10 to 20 watts.

There is however something important to consider. A better way to do it would be to connect the free standing panel to the input of the existing solar panel regulator so there is only one regulator in place. I think from memory that the unit Swift fit is one supplied by Sargent Electrical and can handle solar panels up to a maximum of watts. I have contacted Sargent and they agree with you that the regulator may sense the add on panel. Great job and has given me, a complete novice some understanding. I have a Bailey Unicorn….

All has been good for a year on the road until recently…. The caravan is definately getting power from the car.


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With engine off while connected the 12v system is fine. When i start the engine the 12v system remains on for about a minute then shuts off…. I might deduce a faulty relay? June 14, at If there is, it should give guidance on how to proceed. You will probably need to re-enter your radios security code when you reconnect. Disconnecting the earth terminal from the starting battery and then connecting the charger will not cause any problems while on EHU.

Thanks for the prompt reply. The seller says that the immobiliser etc runs the battery down and he puts it on trickle charge. Hi Stephen The alarms on MH and caravans tend to draw a bit more current than ordinary vehicle manufacturers car alarms and will drain the starting battery quicker than you expect if the engine has not been started and run enough in the last couple of months. Or of course, having the starter battery on trickle charge. July 6, at 6: July 23, at Hi David I have a suspicion that your vehicle towing electrics might be wired with a voltage sensing relay.

The correct way to wire these vehicles is by a relay controlled by the ECU. October 14, at Could I ask, if my vehicles alternator is rated at 80 amps, would this be sufficient to use the modern wiring of having pin 9 permanent live, and the habitation relay activated from pin 10 to switch over to the charging circuit, and connecting both batteries for charging? In other words, does my alternator put out enough to charge both batteries?

October 14, at 9: Hi Gareth A 90 Amp alternator will be well within capacity for looking after the vehicle battery and electrics and charging a leisure battery in the caravan. I could probably adjust it to work fairly soon after the car has started. Hi Gareth 80 Amp will be OK. Do a search on the internet for wiring info for your car.

There should be a fuse that only goes live when the engine is running, not just when the ignition is turned on. Or check with a multimeter. You can then use the output side of this to trigger a standard 30 Amp relay. October 15, at 6: October 15, at 3: October 15, at 4: Hi Gareth Good news! Sounds like you are all on the way, I would put a 3 or 5 amp fuse near the alternator to protect from accidental shorting.

October 22, at 6: I took that out and installed a leisure battery with a smart charger and also upgraded all the florescent lighting to LED which works a treat, so bright, BUT I also installed a car stereo, which I have been fitting for years and I am also pretty good with wiring, but thus time I am at a loss as to what is happening and why. All lighting is fine until I turn on the stereo then they blink when it turns on and the blinking gets worse as the volume is turned up, the more the bass etc the worse the blinking in time with the music.

#36 Charging a leisure battery

I have checked all connections and all is fine. The water heater switch also works off the 12v and when that is switched on they blink but not too much. I must say that I have grabbed the power for the stereo from the lighting system, which most people seem to do and do not have this issue! October 22, at 7: Hi Craig At a quick guess the wiring is too thin. A car stereo amp pulls more current on the bass notes and as the current increases, the voltage drop on thin cable will be noticeable as flickering. Two things you need to do — first increase the size of the main cables from the battery to at least 6mm square supplying the main fuses and to 4mm square supplying the stereo.

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Second — install a voltage regulator on the lighting circuit. October 24, at 5: Hi Simon, many thanks for the input. I have sorted this now by simply wiring the radio direct to the battery, it has been spliced into the light circuitry which as you say is not meant for heavy drain items! Works a treat now, albeit with more agro than I wanted, but still it is in and a neat job done!

Many thanks for your reply. November 12, at Hi Gareth After 5 years of having a 13 pin socket fitted to two vehicles, I have never had an issue with a permanently live pin. I did keep thinking about it in the early days but kind of forgot about it after a while. I did make up a lead that allows me to plug in my smart charger for winter battery maintenance and it doubles as a connection for a 12 volt LED flood light.

March 11, at 6: So thanks for all your time and research and helpful information and replies that have helped me. Peter John Langley said: July 15, at 2: My caravan control panel is showing September 15, at 4: I am considering buying a caravan and towing it with our VW Hillside Leisure conversion campervan.