3 way fridge power question

[stuee]

Hi,
I have a 3 way fridge / freezer.
When i camped last year i ran it on gas all the time but due to Australian weather it was over 30c for a few days and the gas struggled.
i can run on my 100ah deep cycle battery which has 1x 80w solar + 1x 60w solar panel to a regulator to it. The problem is the fridge is power hungry at 12v

Specs
240v - 72w
12v - 72w

What my question is.
I have an 800w inverter, would it be better and last longer running the fridge at 240v on the 800w invert than straight 12v to the battery?

 

[Nigel Goodwin]

Unless you made a typo?, the power requirement is identical at both 240V and 12V - so 12V would be preferred, as you're not making the loses in the inverter.

 

[debe]

If its struggling on Gas, it will be worse running on 12V or 240V. The main problem in Australia with 3 way fridges is they need to be T rated (Tropical). If they aren't then the cabinet insulation is not good enough at those temperatures. 12V compressor fridges are far better here in Australia with high temperatures. 2 main contenders for upright 12V fridges here are Waeco & Engel. I run an 80Liter Waeco upright fridge in my van off 100W Solar system, this will keep fridge temps under4Deg C, in amb temps of nearly 50deg C.

 

[stuee]

hi, thanks for your replies.
Yes the wattage is the same 12v and 240v. i actually have 2 fridges that have about the same power rating.
I know the thermal wrap isnt the best on them as they are cheapos, i think i was reading up on an 4wd forum saying that using gas on a hot day assists in heating up the insulation more so better to use 12v / 240v
For the 12v v's 240v - doesn't an 800w inverter only dray the required current from the battery as required and not draw 800w constant even if no load present?

cheers

 

[debe]

Yes it will only draw the current relevant to the wattage consumed plus a bit extra for inverter inefficiencies. It also helps to use a computer fan to assist in removing heat build up at the back of the fridge as well.

 

[stuee]

So the battery will last longer running both fridges at 240v - 72w through the inverter than direct 12v to the battery at 72w? I was thinking 240v would be better but it's always better to get a second opinion from people better in the know. Also should i mount the fan against the grill blowing into where the heat exchange is.

 

[debe]

Generaly its but at the top vents of the van fridge & draw the hot air from there & exhaust to the outside.

 

[Nigel Goodwin]

So the battery will last longer running both fridges at 240v - 72w through the inverter than direct 12v to the battery at 72w?

No - where has anyone suggested that?.

As I mentioned previously the inverter makes a loss, so uses more power from the battery - 12V would be better.