Nuevo Fridge on 12 Volts

If you do this simple task you'll then find out why running a 3 way fridge on solar won't work...............

Life can be easier if simple rules are followed.....

Pieface wrote:

Already worked out a simple way to do it thanks. Here you go have it for free

Charge the separate 130 amp hour battery from solar. Connect 230 volt Inverter to this 130 amp hour battery. Plug in electric hook up cable tail to inverter. Plug in hook up cable to tail. Plug in hook up cable to main 230 volt inlet in van. Job sorted

Keep all non 230 volt stuff other than the fridge off

Fridge now working from power provided from solar typical consumption of fridge about 50 watts so should keep up for a few days

Life can be simple if you think for yourself and follow your own rules rather than those of the cult or similar

Ok try this, though probably a waste of my time .....

A 3 way Fridge has 3 power inlets, gas, 240vac and 12vdc.
The 12v dc is connected such that it is ONLY powered via split charge relay when the engine is running, this is because the alternator has loads of excess capacity so can afford the 12v 10A load, 120w

Now, in addition, if your read the manuals of the fridge you'll see this 12v cooling is only a maintenance cooling it is insufficient to, for example, cool the fridge from just being switched on, it can only maintain, NOT cool.

Even if this goes beyond you, the current taken by the fridge is constant at 10A, that's a function of the heater resistance in the 12v circuit, it is not thermostatic, it simply runs forever if connected.

So, allowing for the fact that a lead acid battery shouldn't be discharged below 50% capacity, the fridge will simply maintain its current temperature until the battery is at 50% capacity just 6 hours later.

Now, via an inverter, that alone is at best 80% efficient under load, and the fridge now needs 200w on 240 v which is why it has a thermostat, so now, in addition to the inverter inefficiency you need 200w on top of that, let's say 220w which from your 12v battery is 220/12 = 18A so the 130Ah battery to 50% now lasts a whole 3.6hrs.

You can have all that for free, and. please remember that the day when an engineer takes advice from a brick counter is a long way in the future!!!!

If you have the handbook for your fridge it should tell you its average energy consumption over a 24 hr period.  For my fridge its 2.6kWh.  If the voltage is 13V the current will be 2600/13 = 200A for 1 hour (200Ah) which equates to an average steady current of 200/24 = 8.3A.  If the solar panel generates no power overnight for 12 hours, the battery will need to store at least 100Ah which requires a lead acid battery of at least 200Ah capacity.  This assumes no other load on the battery which of course there will be.  The solar panel for the remaining 12 hours in daylight will need to generate 100Ah to recharge the battery and another 100Ah to power the fridge making a total of 200Ah.  This equates to an average steady current of 16.6A over 12 hours which is a big ask for any solar setup and I am sure is much more than yours will deliver.  Converting DC into AC makes matters worse due to the inefficiency of the inverter.  The figures I have used are meant to be illustrative only.

IanH beat me to it.  My figures are slightly different but the message is the same.

There is no such thing as a stupid question and we can all learn from it.  For example, I've just learnt that with a full tank of LPG and no other gas usage my fridge can run on gas on average for about 37.7 days.  I didn't know that.  

The Tech Spec shows an average energy consumption at an ambient temp of 25º of 270 g of LPG per 24 hours.  1 litre of LPG weighs 510g so when my tank is full (20 ltrs) it holds 510 x 20 = 10,200g.  This means that assuming no other gas usage, my fridge will run on average for around 10,200/270 = 37.7 days.  I haven't put it to the test.

I probably have done your test Caraman
Different fridge admittedly but still 3 way.

Just did, in May 3 weeks in N Spain, similar temps and only a few of 21 days on EHU

We are using Campingaz 907 for EU travels for ease of replacement, they are 2.75Kg of Butane

Now, hardly scientific but the fridge was on the whole 3 weeks, but also so was the water heater twice a day, and the cooker for boiling kettles.

The first bottle ran out at 18 days so we used 152g/day. Or in other words, a fridge gas consumption, especially with 20l underslung tanks is almost irrelevant....

On our Warwicks we never got close to using a full tank on any trip, ours are usually 3 weeks. We did leave UK with a full tank however, but easy to top up if ever needed abroad

I wonder if the figures shown in the fridge manual overstate the consumption.  I don't think my arithmetic was wrong.

v8oholic wrote:You haven’t taken account of which setting, perhaps. I normally have it on 1/5 because that’s enough for the cold drinks and water I keep in it. Maybe on 5/5 it would be the quoted figures.

I have been reading these fridge figures in amazement as although I’m impressed by the small amount of gas my fridge uses, I’ve worked it out about 13 days max? The penny has dropped reading the above, I’ve always left mine on 5/5. Why? I’ve absolutely no idea and I like to think I’m a fairly logical person!! 
I will definitely be trying out some lower settings from now on.

So, the conclusion here is that if you have a 3way fridge it doesn't use much gas!!
It is near impossible to run on 12v
It is totally impossible to run on a combo of solar and a big battery and inverter!

Still wish I'd done a Peatlander and gone for a dc compressor one though....

I am willing to give BigPlumbs… sorry Pieface the benefit of the doubt. I will genuinely look forward to his real life experience as it’s all good information whether good or bad.
It wasn’t long ago that I asked exactly the same question. Unfortunately, thanks to the information you guys gave it soon became apparent it was a no go.

I suppose a similar effect can be achieved if the solar regulator has an AES output to a fridge with an AES (Automatic Energy Selector) capability, which I understand allows the fridge to run off solar power when there is sufficient surplus solar available.

All dependent on 2 things, solar panel area and light available

Chris, and Glynne have acres of solar so can do more or less anything within much wider constraints

The average with solar on here will be circa 100w, allowing for the fact that AS supply fitted just 80w.

That is simply not enough to run a 3 way fridge on 12v imho irrespective of battery size, that alone is limited by the ability to charge it from limited solar.....

Just a comment, we all proved in the last day or 2 that, unless on ehu, gas it the answer for the vast majority