12 volt fridge

DeBe · Guru

12 volt fridge

landy · Guru

If its a normal caravan 3 way fridge it will have a very high power draw when it is on 12 volt. (others will know more but I think far to mutch for your solar panel )

Think of it like runing your car head lights, its fine to use them when the car is runing. but will soon flatten the battery if you forget to turn them off when you stop.

Dave.

-- Edited by landy on Sunday 12th of February 2012 10:34:17 PM

Sheba · Guru

I would think it's not connected to the House Batteries, if it shuts off when you turn off the vehicle. Get some-one who knows what they're doing, to connect it properly.

Mine is 240/12V, and so far I've only ever run it on 12V. It runs when the vehicle is turned off, without any trouble at all. I have one House battery, and a large Panel on the roof.

Cheers,

Sheba.

-- Edited by Sheba on Sunday 12th of February 2012 11:19:44 PM

Shogun · Senior Member

Hi all

Can someone please advise me if my fridge runs on 12v when the vehicle is on, why doesnt it run on 12v when I turn the vehicle off?

I have 2x deep cycle house batteries and a 120 watt solar panels.

Is it just a matter of having it wired up to run that way and is it an easy thing to have done?

Thanks in advance for your assistance :)

jimricho · Guru

3 way fridge:

For reasons alluded to in the posts above, if it's a 3 way fridge leave the wiring as it is as this is the correct way to do it. Most likely there is a relay in the fridge circuit to cut the 12v to the fridge when the engine is switched off to ensure that it doesn't flatten the starting battery. Unless you are opening the fridge door (other than very briefly) the fridge should hold its cold when you pull up for lunch or "playlunch". You can run it on gas if you need when stopped for a significant time but don't run it on gas when on the move (you're probably aware of this but I mention it just in case).

The fridge circuit in many tugs does not have this relay installed and their owners have to remember to switch the fridge off (or to gas) if pulled up for all but the briefest stops.

12v 240v 2 way compressor fridge: These are usually wired to the house battery as is Sheba's set-up above.

(edit... typos only)

-- Edited by jimricho on Monday 13th of February 2012 05:30:42 PM

Shogun · Senior Member

Thanks for the replies, I will get it checked out when I get home to see if theres anything I can do

PeterD · Guru

Shogun, what model fridge do you have? If it's one of the AES types it is designed to switch to gas (if the bottle is turned on) a short time after your motor stops. Can you give us the model number?

oldtrack123 · Guru

PeterD wrote:
Shogun, what model fridge do you have? If it's one of the AES types it is designed to switch to gas (if the bottle is turned on) a short time after your motor stops. Can you give us the model number?

Hi

Yes ,the info that should ALWAYS be given or asked for before jumping to conclusionsl

Peter

Jack Mac · Senior Member

I agree with Sheba.

I belive you have a motorhome which would have, I assume house batteries. Possibly your fridge is not connected to this ( these). I would get it checked out by someone qualified. Possibly there is a switch that will switch it over from vehicle to house although I would doubt it. It should be wired to the house battery(s) with a charge from engine to them. A 3way fridge will draw more than a 12/240 but should still be able to run on your house battery, albeit limited depending on your power reserves.

Your lights etc. should be wired to the house battery and I would suggest the fridge should be also.

Jack Mac · Senior Member

Hi Shogun,

Sorry, didn't read your post properly. You have 2 house batteries. they should run the fridge for a limited time. Make sure you get an isolator so that when the vehicle is turned off the fridge, indeed all 12volt installations in you motorhome don't drain the starting battery.

A decent auto electrician should be able to tell you what your current draw is with various appliances turned on. Once you knowwhat your amperage draw is and the capacity of your batteries you should be able to guestimate your usage.

cheers,

Jack

oldtrack123 · Guru

Hi

It seems we still have people jumping to conclusions without enough information

While it most likely that Shogun has a 3way HE HAS NOT CONFIRMED the Model

That can have a significant effect on the way it should be wired

I would also suggest that is highly inadvisable to run any 3way of any battery when that battery is not being charged

They should be interlocked so they can only use the 12v heating element while the engine is running & preferably from the vehicle battery!!

This is the way ALL 3ways should be installed

But depending on MODEL[that question again] there may be other requirements for an independent permanent 12v supply

Model Number ????Please .

Peter

jimricho · Guru

I agree with the comments above about stating the type of fridge (2way 12v/240v compressor type or 3way gas/12v/240v) as the replies are very different in each case. Most vans/RVs use a 3way but 2ways are by no means uncommon.

I have found (from the practical experience of having tried it) that connecting a 3 way to a house battery creates a problem in that it inhibits the effective charging of the house battery from the engine, even when interlocked as described by OT1223 above. I would always advocate connecting a 3way to the starting battery.

For those who have their 3way correctly wired to the starting battery but do not have a device known as a relay (or solenoid switch) installed to cut the supply when the engine is not running (this is what OT123 means by "interlocking") there is a simple solution that doesn't involve a sparky (or DIY) modifying the vehicle's wiring. This is to install a "Fridge Switch" http://www.rvelectronics.com.au/page.asp?parentid=3&parent2id=14 This will detect motion and will cut the (12v) supply to the fridge when the rig is stationary. Anyone with even modest handyperson skills can DIY install one of these.

Assuming Shogun's fridge to be a 3way, as I mentioned in my earlier post, it appears to be correctly installed and no further steps need be taken.

-- Edited by jimricho on Tuesday 14th of February 2012 07:57:40 AM

oldtrack123 · Guru

Hi Jim

We are in full agreement, for a straight out simple 3way

Particularly with:-

[1]NEVER run a 3way from your house battery

[2]Always supply your 3way 12v heating element with it's OWN HEAVY feed from the starter battery

[3]Always have igniton or other means of interlock to prevent fridge operating on start battery ,when engine is not running

The question of model is still valid as other factors may be involved with some models

Hence Peter D's original request for model number

Peter

-- Edited by oldtrack123 on Wednesday 15th of February 2012 11:03:02 AM

Smokeydk · Guru

A mate of mine.said other day......he was going to rip out his 3 way fridge cause it didnt work on 12volt....
I believe 12volt is there when connected to vehicle ...just to maintain the fridges temp......it wont cool it down any further

My mate thought since he had 4 batteries....the fridge would run on that...........sorry....I told him to run it on 240v.couple days before he went away.....turning it to 12v when travelling......then on gas when free camping.....

was a waste of time.as he removed the gas cylinder as he thought gas was too dangerous..he cooks outside the van anyway

Sheba · Guru

Smokeydk wrote:
was a waste of time.as he removed the gas cylinder as he thought gas was too dangerous..he cooks outside the van anyway

I don't like Gas either. Would not have bought my Campervan if it had had a 3-way fridge.

Cheers,

Sheba.

Shogun · Senior Member

Hi all

Thanks for all your suggestions.

When I get home I will take it to someone qualified to advise me whats best.

Brett

PeterD · Guru

Hi Brett, can you please read the model number of the fridge and post it on his thread.

PeterS · Senior Member

I agree fully with most of the above. The HiAce I have just sold ( Safari conversion) with electrolux 3way fridge was wired to work only while engine running by way of a voltage sensing relay. I consulted an Auto Elect friend who told me that is the only way 3way fridges should be wired. He said the 12v supply was only to maintain temp and would not be sufficiant to cool fridge initially so to use 240v for at least 24hrs before your trip and gas when no 240 available on trip.

jimricho · Guru

Your Auto Elect friend is correct. It's surprising how many auto electricians do not install that relay leaving it to the owners to remember to turn the fridge off when they pull up for any length of time, say for lunch or to visit an attraction along the way. I know of more than one who has returned to a flat battery.

As an interesting aside I have tested my Dometic 3way on 14 volts over a 24 hour period (connected to a 14 volt power supply) and found it works as well as any other source so I suspect the main reason for their loss of effectiveness is due to the constant movement of the fridge when travelling.

For comparison I have a voltage booster installed in my rig so the "12v" to the fridge is actually 14v when travelling, and it definitely does not not work as effectively when on the move.

-- Edited by jimricho on Tuesday 28th of February 2012 07:25:19 AM

oldtrack123 · Guru

Hi PeterS

Re "He said the 12v supply was only to maintain temp and would not be sufficiant to cool fridge initially "

Not quite correct , many 3ways have the same rated 12v element as the 240velement,

So IF they recieve adequate voltage there is no reason why performance should be any different

The very common reason for the difference is inadequate cable size both pos & neg from the tug battery to the fridge

MOST Auto Electricians & installers do not take that into account

This is usually made worse by having other loads on the same lines

I suggest that anyone who believes the performance is different to do a simple check

With endine running @ fast idle , all loads that may be running when driving switched on Frig switched to 12v & operating ,CHECK the voltage AT THE FRIDGE TERMINALS

It should be AT LEAST 12v.

Then check the voltage @ the tug battery

If the difference is more than 0.5<0.75v you have undersized cables.

Peter

-- Edited by oldtrack123 on Tuesday 28th of February 2012 03:38:25 PM

PeterS · Senior Member

When vehicle is running a 12v Alt should put out 14.2v so depending on voltage drop ( ie: cable size used to wire fridge) should have at least 13v to fridge anyway so i dont really se an advantage in running a power booster, just get used to the fact that when you stop switch fridge to 240v or gas, it's not that hard. I have aslo been told that a 3way fridge must be level to get max benifit. Can someone confirm this? I guess that applys to all heat exchange type fridges.

Clyde Camel · Veteran Member

Hi Shogun.
Are you saying that if you turn the vehicle off, the fridge doesn't run? Sounds like the socket supplying the fridge is going through the ignition switch and when the vehicle is not running there is no power to the socket. Easy way to test it is if you have a light that you can plug into the socket. See if it goes off when you turn off the engine. You need a socket that is wired (via a fuse) directly to the battery.

I have a Kedron offroad caravan with a 12v Vitro Frigo and 3 x 120w solar panels which are sufficient to take care of the fridge if I am not travelling in the van. You might find that one solar panel isn't enough. In this case you could plug in a battery charger when at home to top up the batteries. I don't have a 3-way fridge so I don't know anything about them.