Hi @mikerezny , absolutely correct on all counts of fridge operation and voltage/size of heating element for 12 volt operation. Cheers.
17' Series Travelling with fridge on 12v
- Thread starter Chris Daly
- Start date
Hi @Bluey,
I also run the 12V for the fridge through the 12-pin plug and have not had any problems in the 11 months we have had the Penguin. After about 3months, I checked the terminals on the plug and found one to be a bit loose. Haven't had that problem again.
Which reminds me. I should go check it again around 12 months. I have a voltmeter permanently wired across the fridge terminals and we check that voltage and compare it with the battery voltage of the tug (via the diagnostic output on the brake controller). We check this as part of our lighting checks each time before we head off. It is usually 0.8V difference. I assume that if there is a connection fault, I will see an increase in the voltage difference.
As an added bonus, if I don't see a voltage difference, the fridge is not drawing any current and I have a problem. There is either a wiring fault, an open circuit element, or, most likely, I haven't switched the fridge over to 12V.
cheers
Mike
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I also believe the sizing of the cabling to prevent voltage drop is very important. On my previous Goldstream Storm I replaced the existing cabling from the battery to the 90l fridge with larger cable (8 BS) and installed 6 BS cable from the house battery to the cars second battery using a 50A Anderson plug. I had the problem of the fridge going sub zero when travelling on 12V after that and made sure any vegetables that didn't like being frozen are kept in the car Engel.
On my Basestation I have connected the 150l fridge directly to the house battery and have wired the battery to the cars second battery using 6 BS and an Anderson plug and it also will go sub zero when on 12V. I'm actually thinking of wiring in a thermostat for the 12V system to better regulate the temperature when travelling.
My alternator cranks out 14.4V and 180 amps so I have no problem keeping my 105 AH AGM starting battery connected by a Traxide to my 55 AH Optima yellow top second battery and the 150 AH AGM house battery charged.
On my Basestation I have connected the 150l fridge directly to the house battery and have wired the battery to the cars second battery using 6 BS and an Anderson plug and it also will go sub zero when on 12V. I'm actually thinking of wiring in a thermostat for the 12V system to better regulate the temperature when travelling.
My alternator cranks out 14.4V and 180 amps so I have no problem keeping my 105 AH AGM starting battery connected by a Traxide to my 55 AH Optima yellow top second battery and the 150 AH AGM house battery charged.
Hi @geedub,
I found a plastic storage box in Kmart that fits almost perfectly in the bottom part of the 90l Dometic RM2350. Left the lid off and it makes a perfect crisper drawer. We also have plastic trays on the other two shelves to trap the cold air. Our fridge also does get down to 0C on 12V when traveling but with the crisper tray and the other trays, we never get anything frozen especially in the crisper drawer.
Another solution, widely used and liked by many others is to install small fans inside the fridge to circulate air and keep the temperature more consistent throughout the fridge.
The problem is that many of the 3-way fridges do not have a thermostat on the 12V element and thus it runs continuously. If the fridge is cold in the morning before we head off, I often switch it off until we stop for lunch and then switch it to 12V before the afternoon drive. I am certainly interested in your progress on putting a thermostat on the 12V element. My first thought would be to investigate controlling it with a Solid State Relay. But I need to investigate that a bit more.
As mentioned by @bigcol and others, the fridge copes reasonably well for a quite a few hours without being switched on as long as it is cold enough to begin with.
cheers
Mike
Hi @geedub , sounds like a good set up!! But a couple of questions for you. What happens when you stop the engine?? I assume you have some sort of auto switching to isolate the fridge current draw from the the house battery and the second battery in the car. Obviously, you have a two battery arrangement in the car to isolate the primary battery as well when engine stopped. In your set up, you are getting full alternator voltage of 14.4 volts to house battery and this voltage is also available to the fridge. No wonder it operates so well!!. In my Penguin, there are three wires via Anderson plug from my tug to the van. The two heavy ones go directly to the fridge (via 20A fuze) and the fridge has NO electrical connection to the house battery. The third wire is a lot thinner and goes to the house battery via the Setec to keep it charged whilst engine running. Unfortunately, it has to pass through a power diode which prevents the current going back to tug. This causes a loss of approx .7 volts, so even if tug alternator output voltage was 14.4 volts or similar, by the time it gets to the van battery, it is down to 13.7 volts, which is just "float" voltage for an AGM battery. I also only have the tug's starter battery, plus a 120AH AGM in the van, but I can see the value in what you have done. Your system circumvents these hassles and keeps voltage high at the 12 volt heating element.
If some or most of your batteries in tug and/or van are a little low, and the fridge was on too, your alternator would really be working to get some juice into these batteries.
I don't have any freezing problems probably because the fridge never gets cold enough on 12 V. Although it can and does on gas or 240 V. I no longer have freezing problems then because I have installed 2 computer fans inside my Thetford fridge which also keeps the ice off the cooling fins, besides keeping fridge temp more even.
I only have thermostatic control of fridge temperature when on 240 V power unfortunately.. You would need a really heavy duty thermostat to control fridge temp whilst on 12 V as current would normally be around 15 or 16 A at 12 volts, but with the higher voltage of 14.4 approx, it would be up around 18 A.
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Hi @mikerezny , I like the idea of crisper trays in the fridge, as long as there was free air flow around each one. My wife uses a crisper on the bottom shelf just beside the 12 V circulating fan I have at the bottom of fridge. This allows the air to move around it and also prevents lettuce, carrots and broccoli from freezing. Open crispers/trays on middle shelf is a great idea as the coldness is trapped in the crisper when you open the door.
Hi @Boots in Action,
unless I am misreading this sentence:
in electrical terms, the heating element is just a resistor. From Ohm's law, the current I, is equal to the voltage across the resistor, V divided by the resistance, R, which in this case is constant. So, with regard to the heating element, the HIGHER the voltage, the HIGHER the current.
cheers
Mike
At the moment I just open the door on the caravan and turn the fridge to the off position if I'm stopping for more than 5 minutes. Of course this wasn't as easy with the Goldstorm and I had to be a contortionist to fit through the door and reach the fridge. I do have 12V coming from the car which is switched by the ignition and is used buy the ESC, charges the breakaway battery and is used by the breakaway battery monitor. I will either install a relay on this to switch the fridge or install a fridge switch. I'll probably go for the relay as I'm pretty sure I have a SSR that is rated at 20A plus hidden away in my shed somewhere I just have to find it!
I would suggest for you that the fridge switch would be the best solution.
I looked it the Jayco wiring and wasn't happy that they ran the fridge 12V through the 12 pin plug and the diameter was way too small in my opinion also the 12V wiring to the setec to charge the battery is a joke.
My alternator already works hard as I have an Engel permanently installed and the Traxide dual battery system shares the load until 12V so my starting battery is often at 12V and the cutout for the second battery is 11.9V. I always have the 150A house battery fully charged before leaving so there is a fair bit of capacity there at first. The car has 200K on it now but I suspect I'll need a new alternator in the next 50K as the diode packs fail due to heat.
I'll try some of the suggestions to keep the veges from freezing before I go the thermostat route but I'm pretty sure I have some controllers lying around at work that can handle the current I just have to check if I can run them on 12V.
Hi @geedub,
you might want to check, but my understanding is that the 12V from the tug going to the AUX input of the Setec will only trickle charge the battery at 0.8A. So, in that case, the wiring is probably adequate.
If the house battery is switched off, then the tug battery will, through the Setec, be supplying the12V to the van. If you ever use this 'feature' then the size of the wiring will need more consideration depending on the van load.
cheers
Mike
Hi @Boots in Action,
unless I am misreading this sentence:
in electrical terms, the heating element is just a resistor. From Ohm's law, the current I, is equal to the voltage across the resistor, V divided by the resistance, R, which in this case is constant. So, with regard to the heating element, the HIGHER the voltage, the HIGHER the current.
cheers
Mike
Hi @mikerezny , @Bellbirdweb , and @geedub , reference my INCORRECT calculation of current when higher voltage is applied across a fixed resistor - heating element. All I can say is Dohh!!! and Doohhh!!!! and Dooohhhh!!!!! What a boo boo. Even the "knuckle heads" know that when voltage is increased, MORE current WILL flow through the resistor. And I like to think (or want to be) a "tech head". Thank goodness there are some members (used to be my colleagues?) who are around to pull me up. I plead guilty, will report to the Principal's office, take 6 of the best, return to elementary tech school and take my place at the bottom of the class and sit in the front row , so the tutor can keep an eye on what I am doing!! After further testing and a successful pass, perhaps you will allow me to join your technical group again??.
The incorrect figure has already been amended to closer to the correct value. So sorry .
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Yes, the wiring is adequate but 0.8A is a joke, Trickle charging is adequate if the van is sitting at home for days or weeks but when driving I want my battery fully charged before the next stop.
Big Mal has 6 B&S from draw bar Anderson to fridge but only 8B&S on the tug and I'm glad I didn't have to buy the vans cable, its about 5 mts worth, the last 10" of cable to the 12v element is the OE for the 12v element, so you have this huge power line connecting to a wire thats about a 12 awg, next time you have your fridge running off your tug just feel this last bit of cable, carefully as it will be very hot, it would be interesting to see the voltage drop at the element itself.....................there is no way I would connect up mine to the house battery, an error would see it suck the life out of it in short time even though my battery is kept fully charged all the time by my panels, in fact there is no charging system from the tug for it at all and I hardly ever use the 240 charger..............my fridge has the AES system which selects power source so if I stop for awhile I turn the gas on and it fires up without even having to go in the van, just have to remember to turn the bottle off later.
My fridge switch is a piggy back fuse block which is plugged into a fuse box circuit that is active with ignition this then connects up to a 35amp relay to the anderson on the back of ute, my aux battery runs the engel in ute and is powered by a solar on the roof, changing an anderson connection will allow the Engel to run off the ute if need be when driving, one day a Cetek 250S or similar will sort things out better, one day....
The Jayco wiring from tug to Setek leaves a lot to be desired, the infamous birds nest under the van is usually a major source of faults later on....and I still haven't fitted a fan inside my fridge, sitting in the shed still waiting.
But I don't think the 12v warrants big spending on it or worry as I had a temp rise of only 2 deg when out Winton way and forgot to turn it on, winter down south the fridge was warmer inside than out.
My fridge switch is a piggy back fuse block which is plugged into a fuse box circuit that is active with ignition this then connects up to a 35amp relay to the anderson on the back of ute, my aux battery runs the engel in ute and is powered by a solar on the roof, changing an anderson connection will allow the Engel to run off the ute if need be when driving, one day a Cetek 250S or similar will sort things out better, one day....
The Jayco wiring from tug to Setek leaves a lot to be desired, the infamous birds nest under the van is usually a major source of faults later on....and I still haven't fitted a fan inside my fridge, sitting in the shed still waiting.
But I don't think the 12v warrants big spending on it or worry as I had a temp rise of only 2 deg when out Winton way and forgot to turn it on, winter down south the fridge was warmer inside than out.
There is a risk connecting directly to the house battery but I needed to get something in place for a trip away. I check that everything (tow hitch, cabling, wheel bearing temps etc) is working correctly every couple of hours when travelling so that if something goes wrong I shouldn't kill my house battery (150AH so it has a far bit of reserve). I will in future set up the system so that if the car becomes disconnected the fridge can't drain the house battery. The internal cabling to the fridge in my Basestation is actually a decent size and I'm comfortable with it carrying 15A continuous, the cable in my Goldstream was inadequate and I upgraded it.
We do long days travelling and have perishables in the fridge and freezer which need to be kept cold and frozen, I don't want to risk travelling with the fridge off.
We do long days travelling and have perishables in the fridge and freezer which need to be kept cold and frozen, I don't want to risk travelling with the fridge off.
Hi @geedub,
do you have something in place to measure the fridge temperature?
We have a small battery operated digital temperature gauge with an internal and external sensors.
Then we wired the external sensor into the interior of the fridge. Sit the gauge on the shelf above the fridge and it always measures the van interior temperature and the fridge temperature.
Bought it on eBay from China for less than $10.
cheers
Mike
do you have something in place to measure the fridge temperature?
We have a small battery operated digital temperature gauge with an internal and external sensors.
Then we wired the external sensor into the interior of the fridge. Sit the gauge on the shelf above the fridge and it always measures the van interior temperature and the fridge temperature.
Bought it on eBay from China for less than $10.
cheers
Mike
Hi @Drover,
I haven't had any problems with the freezer on our Dometic 90L RM 2350. I put a mechanical temperature gauge in the freezer to see how it is going. Usually sits around -14C to -18C. The worst is on really cold nights (6C or less) when the gas doesn't kick in much to keep the freezer cold. On those mornings it has been as high as -10C.
Even trusted it to freeze small amounts of meat, bread etc and it seems to cope ok.
I think the older single door 240V fridges with a pseudo freezer compartment do not work all that well. Remember in the old days never being able to keep ice-cream frozen in them. Worse still, they frost up quickly and then the freezer door doesn't shut and that makes them even worse.
cheers
Mike
Yes, I have an indoor/outdoor thermometer the thermometer is in the fridge with the outdoor sensor in the freezer. Freezer sits at around -16 and I try to keep the fridge between 1 and 4.
Hello @Bigdiggs22, how did you go getting your fridge to operate properly?? On gas and/or electricity? Just how much did you have to alter the van level to get close to suggested tolerances as that would be of interest to a lot of members? I hope that was all that was the problem!!
Someone posted an article recently about the damage that can occur to a 3 way fridge if operated off level.
Despite the wonderful search engine on the forum I can’t find it.
Can anyone point me to the thread/article please ?
Despite the wonderful search engine on the forum
I can’t find it.Can anyone point me to the thread/article please ?
Hi @Bellbirdweb,Someone posted an article recently about the damage that can occur to a 3 way fridge if operated off level.
Despite the wonderful search engine on the forum
Can anyone point me to the thread/article please ?
this is the latest thread I can remember that discusses this issue in detail.
Have a read of the discussion from posting number 15 and onwards.
http://expandasdownunder.com/thread...3/#post-183050"]Travelling with fridge on 12v
Basically, when stationary, the fridge needs to be level left to right looking at the front of the fridge. This ensures that the gas / vapour coming off the top of the boiler condenses properly as it passes down the dimpled tube at the top of the fridge on its way through the cooling fins.
The level front-to back is not as critical.
I just did a Google and found a really good description of this topic.
http://beamalarm.com/Documents/why_does_the_refrigerator_need_to_be_level.html
When travelling, being level is not an issue due to the rocking motion of the van and uphills and downhills evening things out.
cheers
Mike