12/240v fridge + inverter

Submitted: Tuesday, Jul 13, 2004 at 14:41
ThreadID: 14621 Views:3780 Replies:5 FollowUps:8
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I have a problem understanding the following:
if I have a 12/240v fridge + an inverter to watch (240V)TV, does the fridge get the 12v directly from the second battery or does it come from the inverter as 240v. In other words, if I use an inverter, does all the power come from the inverter, or can I run 12v (lights, fridge) seperately from the 240V (TV, laptop, DVD etc.).
Even though I've been reading about it for a week or so, I just can't figure it out from what's been written.
Hope, somebody knows the answer.
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Reply By: Member - Wim (Bris) - Tuesday, Jul 13, 2004 at 14:48

Tuesday, Jul 13, 2004 at 14:48
Should come from the 12vdc. To convert up then back down would be too inefficient.
Would also increase the size of the inverter needed.

Hope this helps
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AnswerID: 67579

Follow Up By: rainer - Tuesday, Jul 13, 2004 at 14:56

Tuesday, Jul 13, 2004 at 14:56
Thanks Wim,
that's what I thought too, but when I read some inverter sites they seem to add everything together and before you know it, you need a 1200W inverter and as far as I can work it out, I only need a 500-600W inverter, Pure Sine that is. (TV, VCR/DVD, Laptop)
FollowupID: 328274

Reply By: Jimbo (WA) - Tuesday, Jul 13, 2004 at 15:00

Tuesday, Jul 13, 2004 at 15:00

You can run stuff off the inverter and at the same time run other stuff from 12 volt outlets. The amount of 12 volt outlets you have (don't forget one of them is powering your inverter) will determine how many 12 volt apliances you can run, of course; and the size of your inverter will determine how much you can run from it at the one time.
AnswerID: 67582

Reply By: Member - Captain (WA) - Tuesday, Jul 13, 2004 at 15:10

Tuesday, Jul 13, 2004 at 15:10
Hi Rainer,

It is far more efficient to run the fridge on 12V directly ( rather than invert 12V DC to 240V AC and run the fridge at 240V) when 240V is not available from mains supply.

However, my 12/240V fridge will automatically use 240V if both power sources are available. Depending on your individual setup, you may have to turn off the inverted 240V to your fridge, otherwise it may automatically use 240V instead of the 12V.

Does your inverter supply power to all your van 240V points, or do you have to plug say TV etc.. into the inverter directly? If directly, simply do not plug your fridge into the inverter and it will automatically run on 12V. However, if inverted 240V is automatically supplied to all outlets, you will have to turn the fridge 240V outlet off when away from mains 240V.

There is no problem running your fridge off the 2nd battery via 12V and the TV off the inverter, also connected to 2nd battery, all at the same time (well, at least till your battery is flat).

I hope all this makes sense.


AnswerID: 67584

Follow Up By: rainer - Tuesday, Jul 13, 2004 at 15:30

Tuesday, Jul 13, 2004 at 15:30
Hi all,
thanks for your replies, they have been very helpful. I'll be buying a campervan at the end of the year and the electrics in it seem to be the trickiest of all components. I would like to be totally self sufficient by way of solar panels, but until I work out how to reduce the power need of a 50l fridge (6amps per hour?incredible!) that seems to be a pipe dream.
FollowupID: 328277

Follow Up By: Rosscoe - Tuesday, Jul 13, 2004 at 16:03

Tuesday, Jul 13, 2004 at 16:03

Maybe worth considering investing in a modern compressor type fridge. Typical brands are Waeco or Engel or dependeing on your intended set up a three way absorption fridge may be the go.
The latter can be switched to run on 240 V ac when it's available, Gas when you're camped and there is no 240 V ac and 12 volt from the vehicle when you're on the move.

Trying to sustain a 6 amp (when cooling) load, 24 hrs a day without mains aint easy.
If you are buying a campervan pay paticular attention to the wire sizes they use to connect to your trailer mounted battery and to the fridge if it's mounted in the camper. Minimise voltage drop wherever you can.
There are a couple of good books that might help. Some may say it's old hat but the fundamentals cannot be refuted.
Check out www.caravanandmotorhomebooks.com.au. I strongly recommend you invest in one or two of the books by Collyn Rivers.
FollowupID: 328279

Follow Up By: rainer - Tuesday, Jul 13, 2004 at 16:47

Tuesday, Jul 13, 2004 at 16:47
Thanks for the good advice Rosscoe,
since I'll be staying 6-12 weeks in the same spot (with some short trips in between)gas is probably the only practicle choice. Any idea, how much gas is used in a new 50l Waeco? BTW, I'll be buying a campervan not a trailer. I'll get a used one of course, but if the electrics aren't up to scratch, I'm prepared to replace the wiring, batteries and fridge and stick a 60w-80w solar panel on the roof. That should be enough to run the TV or laptop or VCR, depending on my use. (2-3 hours a day??)
Those books look very promising.
Let me know about the gas consumption.

FollowupID: 328282

Follow Up By: Rosscoe - Tuesday, Jul 13, 2004 at 17:11

Tuesday, Jul 13, 2004 at 17:11

Not sure if Waeco make threeway fridges. If you are buying secondhand, the campervan will probably have a fridge on board.The most common brand seems to be electrolux. That's what's in my off road caravan. I also run an Engel fridge in the car for those times when I leave the van behind for a day or so to go "exploring". The vehicle has a dual battery system.
Some of the newer campers also have a "house battery"
Can't give you a difinitive answer on gas but I only use it for the fridge prefering to cook outside on a portable stove and or BBQ. I've been on the same bottle for about two years now but I haven't done that many long stays in the one place.
Buy those books if you can aford them but be prepared to read them at least a couple of times (probably more) to come to grips with the theory and pracrical ideas. The one on solar is very good if you hoping to sustain power for any length of time without connecting to mains.
My budget won't let me go sustainable solar but I have estimated it will cost around $1200 to be self sufficient, and that's only for lighting, electric water pump, music, a bit of TV and my Notebook PC, all used very sparingly.
Good luck with hunting down a campervan, they are very popular at the moment. Enjoy your camping.


FollowupID: 328286

Follow Up By: rainer - Tuesday, Jul 13, 2004 at 17:31

Tuesday, Jul 13, 2004 at 17:31
Hi Rosscoe,
thanks again. All the best.
FollowupID: 328289

Reply By: Member - Brian H (WA) - Tuesday, Jul 13, 2004 at 19:13

Tuesday, Jul 13, 2004 at 19:13
looks like you have opened the proverbial can here. There are almost as many options as there are ideas. The 'no name' inverter I run in the trailer has 2 x 240vAC outlets and 1 x 12VDC outlet.
Inverters still aren't all that efficient in terms of battery life. You can buy most appliances for campers/vans t run off 12VDC. This is by far the easiest option. Personally, TV and VCR are 1 thing I try to get away from when I go away.
Happy travels.
AnswerID: 67629

Follow Up By: rainer - Tuesday, Jul 13, 2004 at 21:48

Tuesday, Jul 13, 2004 at 21:48
Thanks Brian,
well maybe eventually I'll be getting away from all those things too. But leaving the city to live and work around the country side at this stage is enough of a change for me at 56.
Thanks for your reply.
FollowupID: 328360

Reply By: -OzyGuy- - Wednesday, Jul 14, 2004 at 08:57

Wednesday, Jul 14, 2004 at 08:57
Your situation of staying in the one place for 6 odd weeks is much similar to myself, so I say from practical experience you should get an 80 Wt Solar pannel (not 60) and a decent duel battery system ie large 'reserve capacity' bigger numbers are better.
A Solar pannel regulator, will depending on the capacity of the battery system if you will need one, they are a benefit if you get one that gives you all the relevant battery voltage information, I don't use one.

One thing to remember is to have the option of removing your Solar pannel from the vehicle and placing it into the sunshine to get your power, while your vehicle is still in the shade, add some decent chain to the 'extension' lead so the pannel dosn't gro legs while you are not watching it :)

As to what brand of fridge is fully dependant on your budget.

As you will be replacing your existing fridge, you probably will have to be putting in a front opening fridge and not a top opener, eliminating the usual brands available, the fridge I use is available with front opening and runs 1/2 the 6 a/h you quote.

As previously stated, wire the Inverter direct to the second battery/s and also run the fridge direct to the same battery with a decent earth.
Try and get an Inverter with at least 2 x 240 v outlets if available for your TV etc.
AnswerID: 67717

Follow Up By: rainer - Wednesday, Jul 14, 2004 at 21:11

Wednesday, Jul 14, 2004 at 21:11
Thanks OzyGuy,
thanks for your great tips. So many, my head's spinning.
FollowupID: 328473

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