Electrical Not all van fridge electrical connections are the same

[Boots in Action]

Recently had a friend on the Sunshine Coast discuss his problems within his van regarding 3 way Dometic fridge operation - or should I say lack of proper operation - and hassles when stopped. With the help of members on this forum, I have a gained a very good knowledge on how, ( in Jayco vans anyway,) 3 way fridges are connected to tug, and how they operate both on and off grid. I mistakenly believed that all van connections were based on this same arrangement ie : 12 volt line from tug to provide power to Setec controller (or other brand) to put some charge into battery and a separate dedicated line direct to fridge terminals to keep fridge going whilst tug motor was running , and that when you stopped, a VSR or other relay type switch disconnected the charge line to prevent tug battery from trying to keep fridge operating until flat! But this is not the same with his 2004 Kedron XL van!! Or maybe it had been changed by previous owner???
He had been told it was necessary (and was doing so) , that every time he stopped, he had to get out of tug, open up van and turn fridge off 12 volt operation and run gas until moving again. The penalty for NOT doing this was a flat VAN battery and a flat tug battery if left long enough. Apparently the tug and van batteries are connected in parallel and so both carry the load until death!! I got him to check with the makers of Kedron vans at Brendale and they confirmed that the van fridge is powered by the van battery and that there is no dedicated line from tug direct to the 12 volt terminals of fridge - it only goes to the van battery. One can imagine that the fridge would not operate too well when voltages of tug and van were down to near 12 volts or below. Kedron at Brendale also told him that when the van is connected to 240 volt power, the first item to receive/absorbe power is a 12 volt charger which then has to charge up the battery to run the fridge until the unit is changed to 240 volt power operation. Is this normal for all Kedron vans of that vintage or later???
IMHO, this is a very crude and antiquated system. I know that my "other half" would not be impressed with this arrangement. Another thing too is that the van has a 100ah Gel battery and only has an unsophisticated older style "linear" 12 volt charger like the basic car charger of years ago, not the best for a Gel battery operation. A "smart" 12 volt charger would look after the battery much better.
Has anyone had this system? I am thinking of changing it to a more modern arrangement with a dedicated line from tug battery terminal direct to 12 volt terminals of fridge with a VSR in line. A separate line (fused) from the VSR could go directly to the battery to charge the battery and a modern "smart" 240 volt charger could replace the old "linear" type. As the the tug battery voltage would probably be too low on start up to close the contacts on the VSR, I would not need to connect a power diode in the circuit as current in this line would only come on when voltage exceeded 13.2 volts after start up.
I would appreciate any advices/warnings and comments before I start trying to improve my friend's older van and solve a few of his hassles with fridge operation.

 

[mikerezny]

Hi @Boots in Action,
you are certainly getting on top of this subject! Good detailed analysis of the current situation including contacting the manufacturer.

There is one school of thought, especially with smart alternators, that running a line from the tug through a dc-dc charger to the van battery and then running from there to the fridge is one way to go. Van battery gets charged correctly, and, if the wiring from the van battery to the fridge is adequate, the fridge will get the voltage it requires to work as well as it will on 240V. As you pointed out, an important issue is to ensure that the fridge does not drain both the car and van batteries. A DC-DC charger will isolate the car battery from the van, and the fridge and I would suggest a motion detector on the fridge circuit would ensure the fridge is only connected when the van is moving.

I have no feelings whether this is better or worse than the method of running the fridge with a dedicated line from the tug battery. Anyone who takes enough time and inclination to understand either way will have a working system. The key is in understanding exactly how the van is wired up so one can make informed decisions in coping with the various scenarios encountered when going camping.

The solution you propose does not include a LVD or LVR to control the van load to protect the van battery. I suspect that you have already thought of that and it will be part of the rewire to support the solar setup.

Another complexity is to the user's present and future requirements for running an inverter to power 240V appliances off-grid.

cheers
Mike

 

[Drover]

Have come across 3 way fridges hooked up to van battery and was amazed since I'm sure the Installation Manual says DON'T............

.I have rewired a few mates vans by running a direct line from tug battery to fridge thru an Anderson of course with a 35/40 amp fuse at the tug and a Fridge Switch or another type of relay at the fridge, when the tug stops the fridge power shuts off, no connection to van battery for the fridge as thats just stupid, since the vans in question had decent solar set ups we never bothered running power to the Setek or whatever was fitted to charge from the tug as it was seen as a waste of money but if no solar then a dedicated line for van battery charging could be run depending on the tug as to how and if a Redarc or Cetek DC-DC was needed......

On my son in laws ute we fitted a Redarc DC-DC charger (BT50 smart alt) to charge the aux battery to run an Engel in the tray then later on when he bought another van we ran a line from the Aux via Anderson direct the van fridge, didn't worry about a fridge switch this time and no van 12v power as heaps of solar. The Redarc keeps the battery juiced up when travelling and often will be running the van and ute fridge with no great hassle......the ute fridge runs 24/7 but I would like to fit a fridge switch for the van but he reckons its unhooked when he stops so no drama...........he can plug a portable panel in to the aux when he's at a worksite/camp as well....I think the Redarc has a LVR but since van is hooked direct to aux battery not much use......

I have found the 240v chargers available from caravansplus to be good value, efficient and bonus made here in Aus...........this is what replaced the Projecta 7 stage earlier this year https://www.caravansplus.com.au/gsl...omatic-battery-charger-12v-30amp-p-12179.html

With my Colorado the fridge power from tug comes direct from battery into a relay which is hooked up to an ignition source, turn key off and the relay shuts off, found a source in the fuse box under bonnet and just used a piggy back fuse plugged into the fuse block and plugged into relay, so damn easy, the RG doesn't have a smart alternator, praise be. Anderson plug at draw bar and the cable runs direct to fridge with another Anderson at the fridge, the cable is too big to link up to fridge wiring and the Anderson makes a good safe step down....No 12v to van though, solar has it covered and have never found a need to date.

Didn't think I would need to go overboard with detail about cable size, fuzes and stuff, I reckon you should be on top of that Booties.

Oh and PS;
before pulling it apart or spending money go over it all with your magic box, as I have found the supposed wiring runs didn't run as presented by dealer/manufacturer on a friends rig, actually made the mod easier and sometimes just far easier to disconnect original wiring and run new stuff........

 

[Drover]

Just wandering a bit, what is your view on these jiggers Booties......... https://www.caravansplus.com.au/pdf/MPPT30-1-manual.pdf

 

[Boots in Action]

Hi @Boots in Action,
you are certainly getting on top of this subject! Good detailed analysis of the current situation including contacting the manufacturer.

There is one school of thought, especially with smart alternators, that running a line from the tug through a dc-dc charger to the van battery and then running from there to the fridge is one way to go. Van battery gets charged correctly, and, if the wiring from the van battery to the fridge is adequate, the fridge will get the voltage it requires to work as well as it will on 240V. As you pointed out, an important issue is to ensure that the fridge does not drain both the car and van batteries. A DC-DC charger will isolate the car battery from the van, and the fridge and I would suggest a motion detector on the fridge circuit would ensure the fridge is only connected when the van is moving.

I have no feelings whether this is better or worse than the method of running the fridge with a dedicated line from the tug battery. Anyone who takes enough time and inclination to understand either way will have a working system. The key is in understanding exactly how the van is wired up so one can make informed decisions in coping with the various scenarios encountered when going camping.

The solution you propose does not include a LVD or LVR to control the van load to protect the van battery. I suspect that you have already thought of that and it will be part of the rewire to support the solar setup.

Another complexity is to the user's present and future requirements for running an inverter to power 240V appliances off-grid.

cheers
Mike

Thanks Mike @mikerezny , actually, I had forgotten about about a LVD and LVR to be included in the circuit, because all I was thinking about was the fridge and battery connections from tug to van. As the wiring and circuits for this old Kedron do not appear to have any of the latest electronic devices to protect the battery from damage when voltage is low, I should be able to include same in an upgraded circuit. Thanks for the great idea as I am already testing my recent purchase of the modular low voltage disconnect switch I have previously referred to.

 

[mikerezny]

Just wandering a bit, what is your view on these jiggers Booties......... https://www.caravansplus.com.au/pdf/MPPT30-1-manual.pdf

Interesting. BUT Although it states 1,700W, it is only a maximum of 425W for a 12V system.
One problem is that it is only a 4 terminal device. The load and battery are on the same terminals. Now, this creates a bit of a problem in that the controller can only measure current out and CANNOT determine if this current is absorbed by the battery or consumed by the load.
If you read the statement on page 3:

The absorption phase is entered following a low battery condition or dawn and is maintained until the battery demand falls below 1.5A.

So, if you have a permanent load exceeding 1.5A, the battery will ALWAYS be charged at bulk/absorption voltage of 14.5V and will never go to float of 13.5V.
This would not be good once the battery is close to fully charged, especially since it can deliver 30A!

I assume that @Boots in Action will have issues with these voltages as having only one fixed setting for sealed batteries, it cannot be ideal for both AGM and GEL. Note, this issue is not only with this regulator. I have suspected that issues exist in attempting to maintain a battery correctly in the presence of a varying load. This is the first time I have found actual evidence to support my suspicions. This is one of the reasons I like the Setec. It separates the load from the battery and seems to manage each separately when connected to 240V. i.e The ST20 has a maximum output of 20A, BUT will supply only a maximum of 10A to the battery. From the Setec manual:

To prevent corrosion on the battery positive plate due to continuous float charging current (VFloat = 13.65V), the unit utilises a storage mode voltage (VStore = 13.25V) when no activity on the battery is detected. This extends the battery life. During store mode, the unit exits to boost mode (VBoost = 14.05V) for 15 minutes every 24hrs to maintain charge in the battery. If battery activity is detected during store mode it exits automatically into float mode.

Ok, Ok, I will shut up and go back to playing with the chippy. @Drover, you got me off my backside yesterday. Jacked up both wheels (Yes, a Penguin has only two) checked that the brakes weren't rubbing and the bearings wern't tight or loose. Even did a tyre rotation to give the spare some work. The calculations for this tyre and axle load seem to indicate 40psi, but I am getting a little more wear on the outside, so I have bumped them up to 44psi. Off, I go again!!!

Sorry.......

cheers
Mike

 

[MDS69]

I fitted a fridge switch to our van and if I had my time again I would go VSR. Reason being and some may say it is inconsequential but if you stop for short periods of anywhere 5 to 15 minutes and think about it 15 minutes is a long period of time and you leave the engine running your fridge is still getting power but with the fridge switch it gets nothing. We all know these 3 ways on 12V need all the help they can get.

 

[Boots in Action]

I fitted a fridge switch to our van and if I had my time again I would go VSR. Reason being and some may say it is inconsequential but if you stop for short periods of anywhere 5 to 15 minutes and think about it 15 minutes is a long period of time and you leave the engine running your fridge is still getting power but with the fridge switch it gets nothing. We all know these 3 ways on 12V need all the help they can get.

Yes @MDS69 , I too like the idea of a VSR to switch power on/off to fridge. Do not have to worry about memory to change switch, does not connect power until tug battery reaches 13.2 volts and disconnects at 12.6 volts - all automatically too!! Yes, costs more than a switch or relay, but can handle multiple circuits requiring similar voltage controlled switching. And no chance of flattening tug battery and only connects when tug battery is high enough after starting.

 

[mikerezny]

I fitted a fridge switch to our van and if I had my time again I would go VSR. Reason being and some may say it is inconsequential but if you stop for short periods of anywhere 5 to 15 minutes and think about it 15 minutes is a long period of time and you leave the engine running your fridge is still getting power but with the fridge switch it gets nothing. We all know these 3 ways on 12V need all the help they can get.

I don't have any trouble running the fridge on 12V. It does depend on:

1: make and model: some 3-ways have a smaller wattage element for 12V compared to 240V. My Dometic RM2350 90l fridge 12V and 240V elements are both 175W. So, there should be no loss of performance switching from 240V to 12V. Earlier 90l fridges had a 125W 12V element. Larger fridges can also have a smaller 12V element.

2: I always have around 13.8V at the fridge terminals (a small voltmeter is permanently wired across the terminals), so I am sure the element is generating at least 175W when we are driving.

I have an ignition-operated relay. There is one small drawback over a fridge switch. When you start the vehicle, the fridge is immediately across the battery. Not normally a problem, but it is drawing 15A and on a cold morning with a battery on the way out it may make the difference between the car starting or not. Sort of the same as learning in the old days to not start your car with the headlights on. If I actually remember, I get around this by starting the car before switching the fridge over to 12V. A VSR is a way better solution.

Initially, I used to worry about the fridge when we were stopping during traveling. After a couple of years, I now don't worry at all. We quite often stop for an hour or so, and just leave the fridge off. However, I do try to park in the shade , or, at least, orientated so the sun is off the fridge side of the van. The fridge will maintain temperature for a hour or so.

I have an external monitor for the fridge temperature, so I have a pretty fair idea of the temperature. Usually, when we arrive, the fridge is colder than when we set out, even when we have stopped for lunch along the way.

I am not a fan of a thee-way fridge. My natural instinct would be to get a compressor fridge. But I just can't be bothered with adding an extra battery and lots of solar to keep it running. After all that, the only real difference would be instead of actively chasing shade and monitoring fridge temperature, I would be chasing the sun and monitoring battery SOC.

cheers
Mike

 

[Drover]

I've forgotten to switch the fridge to 12v years back, Winton to Julia Creek, a tad warm and fridge gained 3 degs so I don't worry now but a VSR is a better option if starting from scratch.

 

[Boots in Action]

Just wandering a bit, what is your view on these jiggers Booties......... https://www.caravansplus.com.au/pdf/MPPT30-1-manual.pdf

Hi @Drover , this unit may have won an award back in 2008, but is now dated and has many limitations on what you can now get and at a cheaper price. There is no display screen, switching battery types by removing cover and changing links is antiquated method( for some people, doing that would be bluddy dangerous - who knows what they may do!!) when this can now be done with external selection switching, 14.5 volts for absorption on a Gel battery could be too high and result in paste drying out during charging and no separate connections for load - they just connect to battery, so no way of knowing/seeing what is being used. Nah, you can do much better than that today anytime - provided of course that you had a genuine MPPT controller. And one other thing, why does it have/need a forward based power diode in the circuit (optional) when modern controllers have this thing incorporated in the unit to prevent current flowing back from controller to solar panel at night?? Suggest pass on this unit!!

Interesting. BUT Although it states 1,700W, it is only a maximum of 425W for a 12V system.
One problem is that it is only a 4 terminal device. The load and battery are on the same terminals. Now, this creates a bit of a problem in that the controller can only measure current out and CANNOT determine if this current is absorbed by the battery or consumed by the load.
If you read the statement on page 3:

The absorption phase is entered following a low battery condition or dawn and is maintained until the battery demand falls below 1.5A.

So, if you have a permanent load exceeding 1.5A, the battery will ALWAYS be charged at bulk/absorption voltage of 14.5V and will never go to float of 13.5V.
This would not be good once the battery is close to fully charged, especially since it can deliver 30A!

I assume that @Boots in Action will have issues with these voltages as having only one fixed setting for sealed batteries, it cannot be ideal for both AGM and GEL. Note, this issue is not only with this regulator. I have suspected that issues exist in attempting to maintain a battery correctly in the presence of a varying load. This is the first time I have found actual evidence to support my suspicions. This is one of the reasons I like the Setec. It separates the load from the battery and seems to manage each separately when connected to 240V. i.e The ST20 has a maximum output of 20A, BUT will supply only a maximum of 10A to the battery. From the Setec manual:

To prevent corrosion on the battery positive plate due to continuous float charging current (VFloat = 13.65V), the unit utilises a storage mode voltage (VStore = 13.25V) when no activity on the battery is detected. This extends the battery life. During store mode, the unit exits to boost mode (VBoost = 14.05V) for 15 minutes every 24hrs to maintain charge in the battery. If battery activity is detected during store mode it exits automatically into float mode.

Ok, Ok, I will shut up and go back to playing with the chippy. @Drover, you got me off my backside yesterday. Jacked up both wheels (Yes, a Penguin has only two) checked that the brakes weren't rubbing and the bearings wern't tight or loose. Even did a tyre rotation to give the spare some work. The calculations for this tyre and axle load seem to indicate 40psi, but I am getting a little more wear on the outside, so I have bumped them up to 44psi. Off, I go again!!!

Sorry.......

cheers
Mike

Hi Mike @mikerezny , I too had wear on the outside on tyres on my Penguin, so now run pressures at 45psi (cold) when fully loaded.

 

[Drover]

Hi @Drover , this unit may have won an award back in 2008, but is now dated and has many limitations on what you can now get and at a cheaper price. There is no display screen,, switching battery types by removing cover and changing links ( for some people, doing that would be bluddy dangerous - who knows what they may do!!) when this is now done with external selection switching, 14.5 volts for absorption on a Gel battery could be too high and result in paste drying out and no separate connections for load - they just connect to battery, so no way of knowing/seeing what is being used. Nah, you can do much better than that today anytime - provided of course that you had a genuine MPPT controller. Pass on that one!!


Hi Mike @mikerezny , I too had wear on the outside on tyres on my Penguin, so now run pressures at 45psi (cold) when fully loaded.

Had no intention of getting one, they have another model as well, way out of my price range just thought it something to throw in the mix, my set up works fine no need to change.

 

[mikerezny]

Had no intention of getting one, they have another model as well, way out of my price range just thought it something to throw in the mix, my set up works fine no need to change.

I do understand. You are just getting bored and having BigMal withdrawal symptoms. That will soon pass and all will be well once again.

cheers
Mike

 

[Boots in Action]

I don't have any trouble running the fridge on 12V. It does depend on:

1: make and model: some 3-ways have a smaller wattage element for 12V compared to 240V. My Dometic RM2350 90l fridge 12V and 240V elements are both 175W. So, there should be no loss of performance switching from 240V to 12V. Earlier 90l fridges had a 125W 12V element. Larger fridges can also have a smaller 12V element.

2: I always have around 13.8V at the fridge terminals (a small voltmeter is permanently wired across the terminals), so I am sure the element is generating at least 175W when we are driving.

I have an ignition-operated relay. There is one small drawback over a fridge switch. When you start the vehicle, the fridge is immediately across the battery. Not normally a problem, but it is drawing 15A and on a cold morning with a battery on the way out it may make the difference between the car starting or not. Sort of the same as learning in the old days to not start your car with the headlights on. If I actually remember, I get around this by starting the car before switching the fridge over to 12V. A VSR is a way better solution.

Initially, I used to worry about the fridge when we were stopping during traveling. After a couple of years, I now don't worry at all. We quite often stop for an hour or so, and just leave the fridge off. However, I do try to park in the shade , or, at least, orientated so the sun is off the fridge side of the van. The fridge will maintain temperature for a hour or so.

I have an external monitor for the fridge temperature, so I have a pretty fair idea of the temperature. Usually, when we arrive, the fridge is colder than when we set out, even when we have stopped for lunch along the way.

I am not a fan of a thee-way fridge. My natural instinct would be to get a compressor fridge. But I just can't be bothered with adding an extra battery and lots of solar to keep it running. After all that, the only real difference would be instead of actively chasing shade and monitoring fridge temperature, I would be chasing the sun and monitoring battery SOC.

cheers
Mike

Yes @mikerezny , all so true in what you say about 3 way fridges. But remember my realisic story of "the hare and the tortoise" when I was camped off grid in hot weather and then it was very overcast, misty and raining for the next 4 days?? He who laughs last laughs loudest!!

 

[Boots in Action]

Have come across 3 way fridges hooked up to van battery and was amazed since I'm sure the Installation Manual says DON'T............

.I have rewired a few mates vans by running a direct line from tug battery to fridge thru an Anderson of course with a 35/40 amp fuse at the tug and a Fridge Switch or another type of relay at the fridge, when the tug stops the fridge power shuts off, no connection to van battery for the fridge as thats just stupid, since the vans in question had decent solar set ups we never bothered running power to the Setek or whatever was fitted to charge from the tug as it was seen as a waste of money but if no solar then a dedicated line for van battery charging could be run depending on the tug as to how and if a Redarc or Cetek DC-DC was needed......

On my son in laws ute we fitted a Redarc DC-DC charger (BT50 smart alt) to charge the aux battery to run an Engel in the tray then later on when he bought another van we ran a line from the Aux via Anderson direct the van fridge, didn't worry about a fridge switch this time and no van 12v power as heaps of solar. The Redarc keeps the battery juiced up when travelling and often will be running the van and ute fridge with no great hassle......the ute fridge runs 24/7 but I would like to fit a fridge switch for the van but he reckons its unhooked when he stops so no drama...........he can plug a portable panel in to the aux when he's at a worksite/camp as well....I think the Redarc has a LVR but since van is hooked direct to aux battery not much use......

I have found the 240v chargers available from caravansplus to be good value, efficient and bonus made here in Aus...........this is what replaced the Projecta 7 stage earlier this year https://www.caravansplus.com.au/gsl...omatic-battery-charger-12v-30amp-p-12179.html

With my Colorado the fridge power from tug comes direct from battery into a relay which is hooked up to an ignition source, turn key off and the relay shuts off, found a source in the fuse box under bonnet and just used a piggy back fuse plugged into the fuse block and plugged into relay, so damn easy, the RG doesn't have a smart alternator, praise be. Anderson plug at draw bar and the cable runs direct to fridge with another Anderson at the fridge, the cable is too big to link up to fridge wiring and the Anderson makes a good safe step down....No 12v to van though, solar has it covered and have never found a need to date.

Didn't think I would need to go overboard with detail about cable size, fuzes and stuff, I reckon you should be on top of that Booties.

Oh and PS;
before pulling it apart or spending money go over it all with your magic box, as I have found the supposed wiring runs didn't run as presented by dealer/manufacturer on a friends rig, actually made the mod easier and sometimes just far easier to disconnect original wiring and run new stuff........

Thanks @Drover for your comments. The last three paragraphs seem to sum it all up especially the PS. A lot will depend on his tug which I think is the dreaded Playdoh which has the a "smart" alternator unfortunately. Obviously you can make some modifications to the alternator output area, but as you said, getting too far away from the original design is fraught with potential problems. Could be a BC to DC charger involved here and another thing, I think he has a portable solar panel with its own regulator. Will see what he expects to do off grid and how often. As he was an airline pilot, I do not think that funds will be a problem, just finding out how much he requires in this upgrade and how much he wants to spend. Should be an interesting exercise!!

 

[Drover]

Yep, sort of thing I like to play with.......

 

[Boots in Action]

Have come across 3 way fridges hooked up to van battery and was amazed since I'm sure the Installation Manual says DON'T............

.I have rewired a few mates vans by running a direct line from tug battery to fridge thru an Anderson of course with a 35/40 amp fuse at the tug and a Fridge Switch or another type of relay at the fridge, when the tug stops the fridge power shuts off, no connection to van battery for the fridge as thats just stupid, since the vans in question had decent solar set ups we never bothered running power to the Setek or whatever was fitted to charge from the tug as it was seen as a waste of money but if no solar then a dedicated line for van battery charging could be run depending on the tug as to how and if a Redarc or Cetek DC-DC was needed......

On my son in laws ute we fitted a Redarc DC-DC charger (BT50 smart alt) to charge the aux battery to run an Engel in the tray then later on when he bought another van we ran a line from the Aux via Anderson direct the van fridge, didn't worry about a fridge switch this time and no van 12v power as heaps of solar. The Redarc keeps the battery juiced up when travelling and often will be running the van and ute fridge with no great hassle......the ute fridge runs 24/7 but I would like to fit a fridge switch for the van but he reckons its unhooked when he stops so no drama...........he can plug a portable panel in to the aux when he's at a worksite/camp as well....I think the Redarc has a LVR but since van is hooked direct to aux battery not much use......

I have found the 240v chargers available from caravansplus to be good value, efficient and bonus made here in Aus...........this is what replaced the Projecta 7 stage earlier this year https://www.caravansplus.com.au/gsl...omatic-battery-charger-12v-30amp-p-12179.html

With my Colorado the fridge power from tug comes direct from battery into a relay which is hooked up to an ignition source, turn key off and the relay shuts off, found a source in the fuse box under bonnet and just used a piggy back fuse plugged into the fuse block and plugged into relay, so damn easy, the RG doesn't have a smart alternator, praise be. Anderson plug at draw bar and the cable runs direct to fridge with another Anderson at the fridge, the cable is too big to link up to fridge wiring and the Anderson makes a good safe step down....No 12v to van though, solar has it covered and have never found a need to date.

Didn't think I would need to go overboard with detail about cable size, fuzes and stuff, I reckon you should be on top of that Booties.

Oh and PS;
before pulling it apart or spending money go over it all with your magic box, as I have found the supposed wiring runs didn't run as presented by dealer/manufacturer on a friends rig, actually made the mod easier and sometimes just far easier to disconnect original wiring and run new stuff........

Hey @Drover and @mikerezny , just had another caravan friend speak to me about the electrical hookup for his 90 L Dometic 3 way fridge in his 2006 Eco Tourer. Seems as his van was one of the first of that type manufactured, the 12 volt hookup of fridge from tug was to van battery, and fridge was connected to van battery. However, he decided to have it changed to the Jayco style ie 12 volt power to fridge from tug only and no direct connection between fridge and van battery. Now he wants to go back to original wiring as out of factory, because he wants it set up as a "touring" vehicle. He states that as he and wife often stop each day for up to a couple of hours to sight see, morning tea, lunch or have extended walks, he needs his fridge to keep working from van battery, which won't happen with current set up when tug not running. Doesn't use the gas normally. I reminded him of the draw (approx 15A plus ) but he replied that was not a problem as he would be able to charge it up battery again at the next park with 240 volt power that night. As he never goes off grid, there is no reliance on van battery power as all operation is from 240 volt source when in a caravan park. He has a point, but I reminded him of the limits of a 120ah AGM and the number of charge cycles he may be able to achieve with this battery set up. In theory, a stop of approx 3 hours each day would use 45ah from a 120ah AGM which leaves battery still above 50% capacity, but if battery not fully charged to max capacity each time in van park, I said he could be pushing the limits. Any thoughts or comments??? Should I dissuade him or let him run his own race??

 

[mikerezny]

First question: Does he have roof top solar. If so, he will be recovering some of that power used by the fridge.
For example, using very rough figures. If he has 150W and a MPPT controller, he could generate about 10A if there is sun and he parks to get it on the panels.
Also, since he is driving during the day, the solar as well as the car may recover a lot as well.
If he drives for 5 hours and stops for 3 hours he may be pretty close to recovering all that the fridge used.
He needs to take some temperature measurements in the fridge to see if he really needs to worry about running the fridge on 12V whilst being parked.

Myself, I wouldn't bother. We motor along with the fridge running on 12V (actually more like 13.8V) and stop whenever and wherever we want along the way. Quite often for an hour or more, sometimes for up to three hours. We try to park in the shade to keep the van (and exterior of the fridge) cool, but always with the sun of the external fridge vents. Now, even if we open up the van for lunch I don't bother running the fridge on gas. But I have a temp gauge in the fridge and I get away with this since I have monitored the temp over the past two years and know that we can do this without the temp getting into the danger zone of 6C. @Drover is certainly of the opinion that the fridge will maintain temp without power for quite a while. If I an not mistaken he doesn't bother running his fridge on 12V even when traveling. After his comments, I became much less concerned about having to keep the fridge running.

Yes, there is the issue of reduced life if a deep cycle battery is discharged regularly below 50%. But the only downside is that the battery will need to be replaced more often. So, roughly speaking, if the longevity goes down from 5 years to 2.5 years, the extra cost is $300 over 5 years, only $60 per year. Less than half a tank of petrol.

Check what fridge he has. It is a pity that most 3-ways don't have thermostat control when running on 12V so the fridge will be consuming power and cooling even though the fridge is at the correct temperature. But some later model AES fridges now have thermostatic control on 12V. If so, then his power usage will not be a continuous 15A.

There is also the option of putting in a second battery if the van can take the extra 30kg without overloading (assuming he even cares). But I think that is probably overkill. If he has access to your expertise, the $300 might be better spent putting in rooftop solar if he doesn't have it already. If he has rooftop solar, then I would suggest a second battery is very much over kill.

cheers
Mike

 

[Drover]

3 hrs ??? Stinking hot day ???? Running on 12v, I shake my head.........better off using gas.....
....hey Mike when I'm driving I used to not worry about 12v but since the rear cam runs off that circuit now it gets a run on 12v tug power but when stopped it goes to gas if its flaming hot......really can't see why you wouldn't just switch to gas but I have come across some people with strange ideas...

 

[Boots in Action]

Recently had a friend on the Sunshine Coast discuss his problems within his van regarding 3 way Dometic fridge operation - or should I say lack of proper operation - and hassles when stopped. With the help of members on this forum, I have a gained a very good knowledge on how, ( in Jayco vans anyway,) 3 way fridges are connected to tug, and how they operate both on and off grid. I mistakenly believed that all van connections were based on this same arrangement ie : 12 volt line from tug to provide power to Setec controller (or other brand) to put some charge into battery and a separate dedicated line direct to fridge terminals to keep fridge going whilst tug motor was running , and that when you stopped, a VSR or other relay type switch disconnected the charge line to prevent tug battery from trying to keep fridge operating until flat! But this is not the same with his 2004 Kedron XL van!! Or maybe it had been changed by previous owner???
He had been told it was necessary (and was doing so) , that every time he stopped, he had to get out of tug, open up van and turn fridge off 12 volt operation and run gas until moving again. The penalty for NOT doing this was a flat VAN battery and a flat tug battery if left long enough. Apparently the tug and van batteries are connected in parallel and so both carry the load until death!! I got him to check with the makers of Kedron vans at Brendale and they confirmed that the van fridge is powered by the van battery and that there is no dedicated line from tug direct to the 12 volt terminals of fridge - it only goes to the van battery. One can imagine that the fridge would not operate too well when voltages of tug and van were down to near 12 volts or below. Kedron at Brendale also told him that when the van is connected to 240 volt power, the first item to receive/absorbe power is a 12 volt charger which then has to charge up the battery to run the fridge until the unit is changed to 240 volt power operation. Is this normal for all Kedron vans of that vintage or later???
IMHO, this is a very crude and antiquated system. I know that my "other half" would not be impressed with this arrangement. Another thing too is that the van has a 100ah Gel battery and only has an unsophisticated older style "linear" 12 volt charger like the basic car charger of years ago, not the best for a Gel battery operation. A "smart" 12 volt charger would look after the battery much better.
Has anyone had this system? I am thinking of changing it to a more modern arrangement with a dedicated line from tug battery terminal direct to 12 volt terminals of fridge with a VSR in line. A separate line (fused) from the VSR could go directly to the battery to charge the battery and a modern "smart" 240 volt charger could replace the old "linear" type. As the the tug battery voltage would probably be too low on start up to close the contacts on the VSR, I would not need to connect a power diode in the circuit as current in this line would only come on when voltage exceeded 13.2 volts after start up.
I would appreciate any advices/warnings and comments before I start trying to improve my friend's older van and solve a few of his hassles with fridge operation.

Thanks Mike @mikerezny for your comments. I will answer/comment on each point you raised:
He has NO solar on roof top or any other solar panel/s. In fact, van is not set up for any solar!!
Yes, while he may be driving a fair bit during the day, his Playdoh (2008 model common rail) has one of those "smart" alternators which would certainly not get his 120ah AGM up to full storage capacity. Refer one of my earlier posts regarding this. In fact, he has remarked that the alternator will not (or takes a very long time?!) to bring tug battery from low to full charge potential. He puts tug battery on a smart charger sometimes and it takes overnight to get to "float" position! I doubt that there would be 13.8 volts at the van battery terminals anyway, which is NOT enough to charge van battery , even if tug battery has been charged sufficiently and before it switches to "free running". Might get him to put smart charger onto van battery when at home and more often??
As far as temperature in fridge is concerned, his fridge was the one I posted a story about some time ago regarding removal, clean, block holes, and other various repairs/baffle fitting etc. Although he now admits more efficient, I do not think he is aware of temp situation too much.
He is on his third van battery in 10 years, so your calculations are pretty close to the mark. Not helped by van sitting for up to 3 months at a time and no battery charging occurring regularly.
His fridge has no thermostatic control when on 12 volts, only on 240 volts AC.
I doubt he is likely to spend money on a solar set up as he is pretty ignorant of solar charging, but I will mention it to him. He frowns at wife and I going "off grid" - never free camps!. The idea of an extra battery in parallel would seem to be an easy fix, but once again he has his own ideas, so I might just listen and let him run with it!! However, he may want me to assist/do? the change over to what he wants after he gets a quote from a "sparkie" to do the job.
Sigh!! Some people do not want to change and to each his own...... until help is needed! Thanks