Fridge 12v supply

[DaveA1]

My lad as a brand new Ssang Yong Musso, tow bar fitted professionally, at the dealers insistence to keep guarantee intact, dedicated wiring and all that. Hooked up to his van, no power to fridge, hooked up to my van, to check, no power to the fridge, so think it's reasonable to assume something wrong with car wiring. Lad had to insist that they look at the car to check, they say,, fitter has fitted tow bars for us before never had any trouble before
Car went back today, fitter saying wiring OK maybe plug connection a bit iffy. . Anyway first thing we do is connect up to my van, power to the fridge,(funny that) BUT fridge is clicking every second, hooked up my motor, fridge OK.
As anyone any idea what could be coursing that ? I would have thought wiring would be heavy enough to limit voltage drop. Want some ammunition to argue our side.

 

[ProfJohnL]

Its not unheard for the cars electrical load to closely match the ability of the alternator at tick over engine speeds. Without the fridge, the voltage may be sufficient to cause the supply relay to activate, but when the fridge load comes on line, it drops the supply voltage below the relays threshold dropping it out again. This cycle may be what happening on the car.

When the car is being driven normally the alternators output rises enough to keep everything happy.

The fitting company is still liable if the supplied system does not work, as it would be a reasonable customer expectation for the ordered system to work properly. The Consumer Rights Act is on your side - however if the problem can be shown to be the car then the fitting company may be off the hook but the car dealer is still responsible because they have insisted on you using their approved fitter, and the car may be faulty which is also their responsibility.

 

[SteveW77]

Is the car fitted with a so called Smart alternator? These are known to cause problems running the fridge.
The one fitted to my Sorento can go for ages producing only12volts until a large demand is put on it then it ups the
output.
Some times my fridge sounds like morse code with the relay clicking in and out.
I find running with the headlights on when towing solves the problem.

 

[CustardAvenger]

As per SteveW77 regarding Smart Alternators:- Check out: https://caravanchronicles.com/2017/04/25/getting-all-charged-up-part-1/

This is a deep dive into resolving electrical supply issues to the caravan. Beyond my technical comfort zone, but may be relevant.

 

[Buckman]

As per SteveW77 regarding Smart Alternators:- Check out: https://caravanchronicles.com/2017/04/25/getting-all-charged-up-part-1/

This is a deep dive into resolving electrical supply issues to the caravan. Beyond my technical comfort zone, but may be relevant.

I think the issue here is no 12v to the fridge while towing. I don't think any one in their right mind would try and use the 12v while the caravan is sited as it will flatten the battery very quickly. Using gas would be a better option.

 

[Hutch]

When I had a tow bar fitted to a new Santa fe, by The dealer, got it home only to find the fridge and ATC were not working, checked the plug . 13 pin. Type. To find the Earth return from the fridge and ATC from the caravan system had not been connected.
Just a thought.

 

[DaveA1]

When I had a tow bar fitted to a new Santa fe, by The dealer, got it home only to find the fridge and ATC were not working, checked the plug . 13 pin. Type. To find the Earth return from the fridge and ATC from the caravan system had not been connected.
Just a thought.

Thanks Hutch
When we plugged into my van the first time, the ATC was activated but there was no power for the fridge, at tick over or running at about 1500 revs.
Motor went back to fitter, came back, power there but switching on and off,(oscillating) on both mine and my lads van fridges.
Lad has gone off today for a weekend near Skeggy, rang me to tell me that fridge power not switching off when ignition turned off.
I'VE JUST THOUGHT!! Some of these relays are adjustable, are they not, if they are set to low say 12.6 volts it would not switch off, but then would it oscillate???
I have fitted all my own tow bars and electrics, to all my motors so far,
Sorry Prof, but WE are going to have a look when he gets back from Skeggy.

 

[ProfJohnL]

I have fitted all my own tow bars and electrics, to all my motors so far,
Sorry Prof, but WE are going to have a look when he gets back from Skeggy.

I see no reason for you to be sorry, why should you be sorry?

 

[DaveA1]

I have fitted all my own tow bars and electrics, to all my motors so far,
Sorry Prof, but WE are going to have a look when he gets back from Skeggy.

I see no reason for you to be sorry, why should you be sorry?

Just your point in another thread that we should never let a dealer avoid his responsibility, which I agreed with, then I'm going to bypass the dealer and hopefully fix something myself.

 

[ProfJohnL]

Well I still do advocate that all sellers and dealers should be made to stand up to their legal responsibilities for selling faulty goods or services.

But ultimately it is a decision of each customer if they want to let sellers off.

Good luck.PJL

 

[ericmark]

I looked at the wiring for caravan sockets, and it seems to have changed through the years, in 2008 the wiring of the car to caravan was included is BS7671:2008 never seen the 12 volt stuff in there before.

According to BS7671 we have just two supplies, Continuous power supply and Power supply controlled by ignition switch, however I know before that we had three supplies two being controlled by ignition switch one to fridge and one to charge caravans battery.

Now BS7671:2008 also states "A721.55.5.1 The circuit to charge an auxiliary battery should be separate from a circuit to operate a refrigerator." the only way this can be done is with a relay in the caravan as now only on ignition feed.

I have not a clue why the IET wanted to set the rules for caravans, Coding for coupled trailer it what it says the pin that was used for second ignition supply, there has always been a problem with pin allocation, pin two was used for vac or air warning on large trailers, but caravans used it for aux supply, then it moved to reversing light which also did hitch and then went to being rear guard fog light. The aux got moved to second plug.

Again years ago we had blocking diodes and spit charge relays the latter was triggered by alternator AL terminal, but as alternators changed we go relays which sensed the voltage instead, all that has now gone with the new breed of alternator and to charge caravan battery you need a DC to DC inverter.

 

[ProfJohnL]

...
Again years ago we had blocking diodes and spit charge relays the latter was triggered by alternator AL terminal, but as alternators changed we go relays which sensed the voltage instead, all that has now gone with the new breed of alternator and to charge caravan battery you need a DC to DC inverter.

Is that just your opinion? Or is now a requirement set out in formal documentation?

 

[Hutch]

Dave, the fridge power supply on my SantaFe , stays live, after turning off the ignition, until the car battery supply voltage drops to about 12.9 volts then a relay somewhere cuts off the supply, confused the hell out of me for a long time.

 

[DaveA1]

Dave, the fridge power supply on my SantaFe , stays live, after turning off the ignition, until the car battery supply voltage drops to about 12.9 volts then a relay somewhere cuts off the supply, confused the hell out of me for a long time.

That's what happens with my Insignia ST been hooking my van up to check every thing works (off to North Wales Thursday) even after a short run, (me trotting back to see if fridge light on, and back), fridge light on for a good few seconds after ignition turned off, but it does go off.
John (my lad) was saying the fridge, it didn't switch off at all. So from having no power from pin 10 ? he now has permanent live.. After it went back to the fitter.

 

[ericmark]

The regulations state:-
A721.55.5 Charging of auxiliary battery and operation of refrigerator
A721.55.5.1 The circuit to charge an auxiliary battery should be separate from a circuit to operate a refrigerator.
A721.55.5.2 The charging circuit for an auxiliary battery should be completed only when the ignition of the towing vehicle is switched on.
A721.55.5.3 The 12 V heating facility of a refrigerator should be completed only when the ignition of the towing vehicle is switched on. This may be performed by a device built into the refrigerator.

Now since there is only one ignition supply to comply with that there must be some relay in the caravan to do it. I personally think it's daft, we have spare pins not used when towing caravans we can arrange two ignition supplies, However we can't really criticise tow-bar electric fitters because they have followed the rules.

As to charging caravan battery I have given up, I have in the past made it work, with the old Lucas alternator I would change the rectifier pack for a Durite one which has the same diodes for the warning output, I then added three extra diodes for the field exciting so had two independent outputs from the alternator, this would charge a second battery just as well as prime mover one, also same idea bringing out a three phase supply from inside the alternator to a diode pack mounted in front of the radiator, however going through 7 pin socket was always a problem I had a battery box in the car boot, and OK for me as an auto electrician to modify alternators but not really a job for standard mechanic, plus today with DC to DC inverters there is no need, The inverter gets around the volt drop problem and even gets around the problem with car engine management switching off alternator so with a DC to DC inverter we can charge the battery in the caravan.

However it requires the inverter to be switches on/off by ignition supply even if it runs on non ignition supply and since it controls the battery charging should be close to battery being charged. So best place would be in caravan not the car.

So that means the simple twin supply to caravan is good enough, with an inverter in caravan there is no real need for the bank of relays which switch lights from caravan to car.

However those relays fitted to modern caravans mean there is a simple way to also fit a second battery in the tow vehicle which if the S plug is plugged in will allow the caravan to auto run from second battery in car, and this would be the permanent supply not ignition.

There is just one problem, many sites do not want you to have car where you could plug in, but the way my caravan is standard wired a second battery in car would work well. Bast place for second battery is in engine compartment, however having room for second battery is another question, old transit van may have two battery carriers but most cars don't.

But still down to same point, unless you have asked for a second battery to be fitted you can't expect it to be fitted as a matter of course, same for second ignition supply, or inverter in the caravan. It is not standard, you have to specially request it.

Personally I use electric hook up and I don't travel for long enough to worry about fridge, however the question is which do you keep the longest, caravan or car? If the car then second battery in car best, if caravan then inverter in caravan best.

What I intend to do is make a lead cig lighter to S socket, so I can put jump starter pack in front box and plug that in when no hook up, Saving caravan battery for motor mover. If I really want I can use the inverter in car to charge the battery pack, however at 0.5A does not really seem worth while.

I did try using split charging relays, I found at start up you could get a 10 to 15 amp charge, however within minutes that has dropped to less than 5A, and for most of trip likely 1A or less, so 110 Ah battery half charged would take 48 hours towing to fully charge, just does not seem worth the effort.

If your going to charge a second battery from car, then you want it to charge in around 6 hours, only way it will do that is with a DC to DC stage charger. I have considered a 12 volt to 230 volt inverter in the car and a 230 volt supply to caravan using caravans charger, less volt drop and good regulation, however having a 230 volt feed to caravan while towing raises safety issues.

A 20 Ah VRLA battery in the car is likely best option, again safety issues, but I carry a battery pack to jump start with which has a 20 Ah battery inside it, I have seen no warning about carrying jump start battery packs in a car, so as long as the battery is in a protective box can't really see a problem. Mine came with a cig lighter to cig lighter lead to charge it from car, so all I need is a cig lighter to S socket lead.

 

[ProfJohnL]

Hello ericmark.

The regulations require separate supplies to the caravan battery and fridge, so that the fridge cannot draw power from the caravan battery when the tow vehicle is not producing enough 12V power. I am aware of a split charge diode pack that was tried, but they ran into problems of diodes burning out, and the voltage fed to the caravan would always be at least 1.2V lower because of the forward diode junction voltage drops. This in conjunction with the losses due to the wire gauge used often meant there was insufficient voltage to raise the battery above about half charged.

I concur with your reasons for looking at DC to DC or even DC to AC inverters to help reduce cable losses. With present equipment 12 to 230V ac would be relatively easy to achieve, but there are safety concerns. The concerns could be easily addressed if the construction sites 110V ac protocol were adopted, but it would mean a lot of additional equipment, and a similar argument would apply to using a DC to DC converter to perhaps 48V, it would reduce the current to 25% of the 12V. Some quite substantial DC power Buck and Boost systems are available from China

The would need to be installed in proper boxes to protect from the elements and to provide the necessary heat sinking, but for example a DC switching boost regulator taking 12V power from close to the alternator, could raise its voltage to about 48V (to keep it within the safe low voltage regulations) This would be wired to the caravan where two separate 48 to 12 buck regulators would produce the battery charge and fridge run circuits.

I suggest two units as one could provide a well regulated optimal battery charge voltage,(14V) and the other could be set differently to keep the fridge running at say 11V. The Buck regulator circuits would provide the DC isolation between battery circuit and the fridge.

Not perhaps as electrically efficient as 230V ac, but a big improvement over 12V,

 

[DaveA1]

Dave, the fridge power supply on my SantaFe , stays live, after turning off the ignition, until the car battery supply voltage drops to about 12.9 volts then a relay somewhere cuts off the supply, confused the hell out of me for a long time.

That's what happens with my Insignia ST been hooking my van up to check every thing works (off to North Wales Thursday) even after a short run, (me trotting back to see if fridge light on, and back), fridge light on for a good few seconds after ignition turned off, but it does go off.
John (my lad) was saying the fridge, it didn't switch off at all. So from having no power from pin 10 ? he now has permanent live.. After it went back to the fitter.

Things have moved on Hutch. Lad went to Skeggy, as I said. Then he found out if fridge switch off, lights worked, apart from when he put hand brake on, both front marker lights when out. Switch fridge on and all lights worked together, oscillating with the fridge. So I'm not touching it, car going back to dealer, to fix or else.

 

[DaveA1]

The regulations state:-
A721.55.5 Charging of auxiliary battery and operation of refrigerator
A721.55.5.1 The circuit to charge an auxiliary battery should be separate from a circuit to operate a refrigerator.
A721.55.5.2 The charging circuit for an auxiliary battery should be completed only when the ignition of the towing vehicle is switched on.
A721.55.5.3 The 12 V heating facility of a refrigerator should be completed only when the ignition of the towing vehicle is switched on. This may be performed by a device built into the refrigerator.

Now since there is only one ignition supply to comply with that there must be some relay in the caravan to do it. I personally think it's daft, we have spare pins not used when towing caravans we can arrange two ignition
supplies, However we can't really criticise tow-bar electric fitters because they have followed the rules.

As to charging caravan battery I have given up, I have in the past made it work, with the old Lucas alternator I would change the rectifier pack for a Durite one which has the same diodes for the warning output, I then added three extra diodes for the field exciting so had two independent outputs from the alternator, this would charge a second battery just as well as prime mover one, also same idea bringing out a three phase supply from inside the alternator to a diode pack mounted in front of the radiator, however going through 7 pin socket was always a problem I had a battery box in the car boot, and OK for me as an auto electrician to modify alternators but not really a job for standard mechanic, plus today with DC to DC inverters there is no need, The inverter gets around the volt drop problem and even gets around the problem with car engine management switching off alternator so with a DC to DC inverter we can charge the battery in the caravan.

However it requires the inverter to be switches on/off by ignition supply even if it runs on non ignition supply and since it controls the battery charging should be close to battery being charged. So best place would be in caravan not the car.

So that means the simple twin supply to caravan is good enough, with an inverter in caravan there is no real need for the bank of relays which switch lights from caravan to car.

However those relays fitted to modern caravans mean there is a simple way to also fit a second battery in the tow vehicle which if the S plug is plugged in will allow the caravan to auto run from second battery in car, and this would be the permanent supply not ignition.

There is just one problem, many sites do not want you to have car where you could plug in, but the way my caravan is standard wired a second battery in car would work well. Bast place for second battery is in engine compartment, however having room for second battery is another question, old transit van may have two battery carriers but most cars don't.

But still down to same point, unless you have asked for a second battery to be fitted you can't expect it to be fitted as a matter of course, same for second ignition supply, or inverter in the caravan. It is not standard, you have to specially request it.

Personally I use electric hook up and I don't travel for long enough to worry about fridge, however the question is which do you keep the longest, caravan or car? If the car then second battery in car best, if caravan then inverter in caravan best.

What I intend to do is make a lead cig lighter to S socket, so I can put jump starter pack in front box and plug that in when no hook up, Saving caravan battery for motor mover. If I really want I can use the inverter in car to charge the battery pack, however at 0.5A does not really seem worth while.

I did try using split charging relays, I found at start up you could get a 10 to 15 amp charge, however within minutes that has dropped to less than 5A, and for most of trip likely 1A or less, so 110 Ah battery half charged would take 48 hours towing to fully charge, just does not seem worth the effort.

If your going to charge a second battery from car, then you want it to charge in around 6 hours, only way it will do that is with a DC to DC stage charger. I have considered a 12 volt to 230 volt inverter in the car and a 230 volt supply to caravan using caravans charger, less volt drop and good regulation, however having a 230 volt feed to caravan while towing raises safety issues.

A 20 Ah VRLA battery in the car is likely best option, again safety issues, but I carry a battery pack to jump start with which has a 20 Ah battery inside it, I have seen no warning about carrying jump start battery packs in a car, so as long as the battery is in a protective box can't really see a problem. Mine came with a cig lighter to cig lighter lead to charge it from car, so all I need is a cig lighter to S socket lead.

I don't know whether the above relates to my OP or not. I keep things as simple as possible, take a tyre, all I'm interested in is Age, its capacities ie load/speed, its condition and size and tread depth. I'm sure there is chapter and verse of regulations that cover tyres, I'm not interested, I'll leave that to others, I don't need them to purchase a set of tyres. I had a couple of useful suggestions and I thank them. the car is going back to the dealers now and my lad dose not want it back until the tow bar electrics are work as they should. All my lad is interested in is a working fridge and lights.

 

[ericmark]

I do not agree with the IET/BSi getting involved with the extra low voltage wiring and systems in a caravan. Even if there are some trailers which need a warning lamp to show if the vacuum tank is empty, this does not apply to 99.9% of caravans so there is no reason why the unused pins in the 7 pin S type plug can't be used for a second ignition/fuel cut off supply. At one time the standard relay used for towing had two sets of contacts one for caravan battery and one for fridge.

Back to basics reason for relay
1) To ensure one starting tow vehicle current is not drawn from caravan battery.
2) To ensure when engine is not running the caravan does not over discharge the tow vehicles battery.
The blocking diode does what would seem a perfect job, Sterling power does a range of diodes

starting at 70A with is likely too small for modern car, but also do a 90A, 130A, 160A and 200A versions. Volt drop is quoted with this new breed as 0.75 volt much improved to old type. I am sure they work A1 on boats where the batteries are close to each other and alternator not controlled by vehicle engine management system.

Sterling Power also do DC to DC inverters and battery discharge limiters, with a narrow boat typically having 4 x 180 Ah batteries one for engine and three for domestic battery life is important, they cost a lot to renew, and the ability to recharge from a shore supply is limited, they typically have 2 alternators on the engine and often a special alternator regulator or an alternator to battery charger, so the domestic batteries are pulse charged and the engine battery float charged from same pair of alternators.

To my mind this is over kill for a caravan, there are some huge differences.
1) Engine management stopping any external control to battery charging.
2) Long cable run between batteries with plug and socket in the middle. (Bow thrusters do have long cable run to local battery but not alternative method other than DC to DC to charge them.)
3) Short time with engine alternator running, typical narrow boat 8 hours per day, caravan unlikely to even average 3 hours per day.
4) Narrow boats can't vent under the fridge, they would sink, so there is often no gas option for safety reasons.
5) Never seen a washing machine in a caravan used to tour with, so caravan loads a lot lower.

There may be special cases, some one may want to tour to Turkey and back being on the road for an extended time with limited electric hook-up. However most of use do not really need for the few hours travelling per day to have either fridge or battery charging from car. Fridge cold before we start and hook-up on arrival is normally ample.

If something special needs keeping cold, snake bit serum for example, a cool box in car is likely better option.

 

[Hutch]

Ericmark, I don't think your helping DaveA1, s original problem.
Oh and when we tour France we have a lightweight washing machine with spin dryer. 10kg.

 

[Dustydog]

Eric mark
That’s a very good answer and sets out a good stall.
The one thing that seems to be missing for me is the infamous 12s pin burn out . This is caused by using one earth terminal to carry the return from both the fridge and the battery. The fix is well documented where a spare terminal is used and wired independently to an independent earth point.