Solar powered beer fridge

The fridge is smart enough to swap over. Check out the model number on google and you will find whether I am right. Older models may not be as smart.

I used to leave mine plugged into 12 volt batteries and a generator when camping for weeks at a time in the territory. Never had a problem.

I think you will find that your fridge will only run on 12v when there is no 240v available so there is no point leaving it plugged in to both
Probably better to have a 240v charger connected to the battery via a timer and run it for say an hour a day or more if needed. On the days the solar is keeping up with the fridge the charger will only sit in float mode so wouldn't consume a lot of power

What you are finding is typical of inefficiencies found in solar/ battery/ fridge systems.

My maths indicate that to be in the race for long term reliability you need to have at least 160 watts of solar panel and 100 AH of battery to keep a 40 litre fridge, run as a fridge, running reliably.

NOW if your panels are not delivering full rated output in full sun, your battery is getting a bit sad and ya fridge is running too cold or not well insulated….these losses all add up very quickly…resulting in beverage disappointment and social stigma

What you have here is an opportunity to get your solar/fridge/battery system sorted out.
So you need to tell her in doors that this whole cold beer thing is all in the interests of science.

So places to look for improvement.

1/ make sure your panels are clean, in clear sun all day and are not subject to unnecessary heat….all these things will reduce efficiency……..CONsiderably

2/ upgrade your cabling between the panels and the battery and if you can relocate the regulator close to the battery.
A learned member on another forum, proved by scientific methods ( beer may have been involved) that the folding panel as he received from the supplier was outputting less than 50% of its rated output.
Further by scientific methods ( more beer may have been involved over a significant test period) he proved that only by replacing the cables and relocating the existing regulator close to the battery. He could produce at last as good as the specified output from the panels into his battery.

3/ consider your regulator…..a better regulator may or may not improve your charge rate.

4/ Consider your battery…..if it has some age to it, it may not have anywhere near its original storage capacity, it may not be accepting charge efficiently and it my be leaking charge.

5/ insulate your fridge…..almost all fridges are poorly insulated……so ya fridge has been sitting on the floor running for a few days…..pick it up and feel the cold patch underneath….this represents losses of cool.
Just putting a slab or styro under and a folded blanket on top of your fridge can improve efficiency no end.
Best to get some sort of insulated cover.
Keep ya fridge in a cool place.

6/ consider your fridge temperature.
The lower the fridge temperature the higher the losses and the less efficient the refrigeration system.
Standard safe fridge temperature is considered to be around +2C…however optimum beer drinking temperature is considered to be –2C………yeh well needs must.
If you are finding –2C is not doing it for you look for other inefficiencies…..chill your glasses…..pouring cold beer into a hot glass is a sad loss of efficency.
If you are drinking from cans or stubbies….DO NOT do so without proper insulative equipment……pre-chill you stubby holder too.

Be aware you may need assistance in your scientific endevours, I am sure there are those who will assist you in your scientific endevours.

cheers

To answer your question, I think.
You can leave both leads plugged in permanently.
The 12 volt connected to the battery so the fridge runs. Once 240 volt power is supplied to the fridge it take precedence, the 12 volt side is isolated.
So hook it all up and turn the power point on when the solar / battery system is a bit slow. Turn it off when the sun is out.
Mine sits in the ute with both leads plugged in to the fridge, the 240 volt plug is tied to the fridge handle ready to plug in to a power point if I want to use 240 volt power and never had an issue, its what it is designed to do.

Thanks for all the responses. I am only using a used recharged marine battery that someone was going to throw out. Once charged on the Projecta at home it holds 13v. It's just that after a few cloudy days in a row she starts to drain a bit as I am guessing the battery is 2-3 years old.
At this stage it's a bit of a hobby getting "something for nothing" although it will take a while to recover costs. The idea is to. Have it run on so.ar as much as possible. I have also wired in another 12v cigarette lighter plug on the battery box and use this to recharge phones and iPads etc. a bit of bun. Thanks to all.