Solar powered beer fridge

Submitted: Friday, Nov 28, 2014 at 19:58
ThreadID: 110275 Views:2605 Replies:5 FollowUps:5
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When I am not out on the road touring our Engel 40 litre fridge serves as a beer fridge at home. It also serves as a vodka fridge and a Sauvignon Blanc fridge.
Instead of having my folding 140w solar panels sitting in the shed I thought I would stick it on the roof of the house and run it through a marine battery. That way the missus can't argue over the additional electricity costs.

However, with the weather being iffy in the Top End it's a task to continually unplug the solar to 240v regularly and back again when the sun comes out. Can't have the beer going cold.
So with this 1st world problem, what would happen if you left both 240v and 12v solar plugs plugged in? Would one system override the other? Would you blow the fridge up? I'm not sure, but not willing to experiment with a $1500 fridge. It's a light hearted thread, but would be good to know anyway.

Thanks to all fellow EO travellers.
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Reply By: Bigfish - Friday, Nov 28, 2014 at 20:17

Friday, Nov 28, 2014 at 20:17
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.
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Follow Up By: Top End Az - Friday, Nov 28, 2014 at 20:24

Friday, Nov 28, 2014 at 20:24
It's only 18 months old. So does it prefer 240 or 12v?
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Follow Up By: HKB Electronics - Friday, Nov 28, 2014 at 22:03

Friday, Nov 28, 2014 at 22:03
Most fridges will switch to 240V if it is available to save the battery. Your fridge might have a priority selection setting though?

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Follow Up By: pepper2 - Saturday, Nov 29, 2014 at 10:03

Saturday, Nov 29, 2014 at 10:03
I am surprised your solar cant keep up with the fridges power needs especially considering you are not using it as a freezer ie set below zero degrees.

My fridge is around 52 litres and 160w of solar happily maintains minus 5 deg c for weeks on end charging into a 100 amp deep cycle battery. (This is without running the vehicles engine at any time.)
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Follow Up By: Member Andys Adventures - Saturday, Nov 29, 2014 at 12:07

Saturday, Nov 29, 2014 at 12:07
Agree with Pepper 2,
I have a 40lt and 2/ 80ah batteries being charged with a 160W solar system and never need to charge from 240 for over 6 months a year while in the NT.
But then again I don't use it as a beer fridge so only gets open twice a day.

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Reply By: AlbyNSW - Friday, Nov 28, 2014 at 22:38

Friday, Nov 28, 2014 at 22:38
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
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Reply By: The Bantam - Saturday, Nov 29, 2014 at 11:33

Saturday, Nov 29, 2014 at 11:33
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.

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Follow Up By: Frank P (NSW) - Saturday, Nov 29, 2014 at 11:55

Saturday, Nov 29, 2014 at 11:55
I like the science, Bantam:-)



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Reply By: MactrolPod - Saturday, Nov 29, 2014 at 17:20

Saturday, Nov 29, 2014 at 17:20
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.
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Reply By: Top End Az - Saturday, Nov 29, 2014 at 18:53

Saturday, Nov 29, 2014 at 18:53
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 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.
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