How many batteries

[Gibbo]

???

 

How would you test a fridge with a battery monitor?

 

He's a knob. He has decided something in his head which is utter crap but, like most stupid people, it stays there despite evidence to the contrary.

[Robin2]

No. I tested about 20 fridges (I forget the exact number). A completely random mixture of makes and models. Some 12 volters were identical to some 230 volters but had been converted by (remember these people?) Batts. Some were completely custom built 12 volt fridges. Some were standard fridges that the manufacturer happened to also do as 12 volts. It really was a completely random mixture.

 

The idea of testing 20 random fridges as opposed to a certain 12 and a 230 volt model of the identical fridge was to get some real world comparative figures, on average, of what people were likely to experience in the real world, as opposed to some definite figures for just a single model.

 

Broken finger edit.

 

PS. I almost forgot. I had done the almost identical test about 5 to 10 years earlier (this would be about 1985 IIRC) and at that time there was almsot no difference whatsoever between a 12 volt fridge running from the batteries and a 230 volt fridge running from an inverter. Don't hold me to the dates, they are wild guesses.

 

It is hard to know what to make of your tests without knowing the types of fridge and the testing procedure. I would expect considerable differences between different models, but not so much between identical fridges with different motors - unless more than the motor was changed. After all there is no intrinsic difference between a 12v dc motor and a 230v ac motor - they both convert electricity into rotational energy and both are "theoretically" 100% efficient.

[Gibbo]

It is hard to know what to make of your tests without knowing the types of fridge and the testing procedure. I would expect considerable differences between different models, but not so much between identical fridges with different motors - unless more than the motor was changed. After all there is no intrinsic difference between a 12v dc motor and a 230v ac motor - they both convert electricity into rotational energy and both are "theoretically" 100% efficient.

 

Agreed. However the interesting thing is that all the 230 volt fridges were less efficient than all the 12 volt fridges. No exceptions. No crossover.

 

Another broken finger edit.

Edited August 22, 2011 by Gibbo

[Bobbybass]

He's a knob. He has decided something in his head which is utter crap but, like most stupid people, it stays there despite evidence to the contrary.

Aha...it is possible to wind up the great Gibbo !!

[Gibbo]

Aha...it is possible to wind up the great Gibbo !!

 

LOL. If you saw me sat here laughing you might reach a different conclusion.

[Bobbybass]

LOL. If you saw me sat here laughing you might reach a different conclusion.

[smileypete]

In January diddly-squit, in June twice as much (on a good day) as I need, but bear in mind now that 'high' summer is tending to be overcast and spring and autumn are the sunniest times.

Maybe try to use the surplus to run a big fan to help cool the boat, or make plenty of ice cubes for drinks.

 

I s'pose adding more solar than can be used still offsets some engine/generator use but extends the payback time of the panels.

 

 

Just a point on manufacturers stats. Surely they have to prove within a reasonable percentage thay the figures the attest to are correct. These figures after all are all to do with the Eco rating system and are awarded ratings as such.

I think the standard test is 25°C ambient, fridge has free ventilation on all sides, no door opening/closing.

 

Something that can be done is to feel how hot the condenser grille gets at the back. If it does get more than warm then adding some forced cooling to it will boost efficiency.

 

 

After all there is no intrinsic difference between a 12v dc motor and a 230v ac motor - they both convert electricity into rotational energy and both are "theoretically" 100% efficient.

Ya need to learn abit more about DC and AC motors!!!

 

cheers,

Pete.

[nb Innisfree]

Agreed. However the interesting thing is that all the 230 volt fridges were less efficient than all the 12 volt fridges. No exceptions. No crossover.

 

Another broken finger edit.

 

Your last tests were 10 or 15 years ago? Is it possible 230v fridge efficiency has improved since then? Fridge efficiency does seem to be at the forefront lately.

[Gibbo]

Your last tests were 10 or 15 years ago? Is it possible 230v fridge efficiency has improved since then? Fridge efficiency does seem to be at the forefront lately.

 

Absolutely possible. The point is that there was a difference between 12 and 230 volt fridges.

[Robin2]

Agreed. However the interesting thing is that all the 230 volt fridges were less efficient than all the 12 volt fridges. No exceptions. No crossover.

 

Another broken finger edit.

 

I don't doubt your sincerity but I can't see how you can make that statement without comparing like with like. There is also the question of whether there might have been better 230v fridges or worse 12v ones that you did not test (for whatever reason). Not to mention the possibility that the examples you had might not have been typical of their types.

 

On the other hand if you can publish your methodology and results they would probably provide very good guidance for readers (including me) and we can put the question of the validity of manufacturers claims to one side.

[nb Innisfree]

I don't doubt your sincerity but I can't see how you can make that statement without comparing like with like. There is also the question of whether there might have been better 230v fridges or worse 12v ones that you did not test (for whatever reason). Not to mention the possibility that the examples you had might not have been typical of their types.

 

On the other hand if you can publish your methodology and results they would probably provide very good guidance for readers (including me) and we can put the question of the validity of manufacturers claims to one side.

 

He would need to do the tests again with current models and if he did agree to do it who would pay him?

[bizzard]

Well i wouldn't have any electric fridge on my boat thanks very much,not even if it was given to me.

I''ll be sticking with my gas one.Same fridge i've had for 13 years,i service it during the winter and then forget it.And my battery is always tip top. bizzard

[Gibbo]

I don't doubt your sincerity but I can't see how you can make that statement without comparing like with like. There is also the question of whether there might have been better 230v fridges or worse 12v ones that you did not test (for whatever reason). Not to mention the possibility that the examples you had might not have been typical of their types.

 

On the other hand if you can publish your methodology and results they would probably provide very good guidance for readers (including me) and we can put the question of the validity of manufacturers claims to one side.

 

You're trying but you're missing the point...

 

It was a random, controlled test, of random fridges. Because that's exactly what someone gets when they buy a fridge. They get a random fridge.

 

On that basis the test was perfect and could not have been improved.

[smileypete]

It seems clear to me - did you test two otherwise identical fridges with the only difference being that one had a 230v motor and the other had a 12v or 24v DC motor? And if so I would be interested to know the brands and the results.

OK...

 

Note that these 2 fridges have exactly the same cabinet, the 12V one is based on a LEC cabinet.

 

12v fridge, 125kWh/yr

230V fridge, 180kWh/yr

 

So the 12v fridge uses 30% less energy, and much of this is down to the DC compressor.

 

cheers,

Pete.

[Robbo]

So the 12v fridge uses 30% less energy, and much of this is down to the DC compressor.

 

There's a 12v fridge out there ( I forget the name ), that cools the fridge more when the engine is running, so doesn't need to run as much when on battery. Even if this fridge isn't as efficient if ran in normal mode, it seems it would be better battery wise.

[Robin2]

OK...

 

Note that these 2 fridges have exactly the same cabinet, the 12V one is based on a LEC cabinet.

 

12v fridge, 125kWh/yr

230V fridge, 180kWh/yr

 

So the 12v fridge uses 30% less energy, and much of this is down to the DC compressor.

 

cheers,

Pete.

 

One swallow doesn't make a summer

 

And it's not clear that the Shoreline figure is based on the standard EU test.

 

And ...

 

... please explain why DC makes a difference.

[Gibbo]

One swallow doesn't make a summer

 

Perhaps not. But it does prove that she loves you.

[Robin2]

Perhaps not. But it does prove that she loves you.

 

Unfortunately not even that is true

[WotEver]

Perhaps not. But it does prove that she loves you.

 

... please explain why DC makes a difference.

Take a look here for a little bit of info.

 

Tony

[Justme]

 

Note that these 2 fridges have exactly the same cabinet, the 12V one is based on a LEC cabinet.

 

So the 12v fridge uses 30% less energy, and much of this is down to the DC compressor.

 

 

So that begs the question.

 

Why dont they make all fridges as 12v ones & fit an internal converter from the mains? 30% is a large margin for losses in the conversion. They would then have much better rated fridges than all the other sellers so could justify the small extra retail cost of the converter.

 

 

The ones that run more when the engine is on will be the best solution & its one that is coming soon for mains ones as well when the smart grid rolls out.

[Chris Pink]

So that begs the question.

 

Why dont they make all fridges as 12v ones & fit an internal converter from the mains? 30% is a large margin for losses in the conversion. They would then have much better rated fridges than all the other sellers so could justify the small extra retail cost of the converter.

 

 

The ones that run more when the engine is on will be the best solution & its one that is coming soon for mains ones as well when the smart grid rolls out.

 

The logical answer is also the conclusion I would draw from Gibbo's test - that energy efficiency is not as important as cost in a domestic fridge and is a far more important factor in a 12V unit.

[Robin2]

Take a look here for a little bit of info.

 

I didn't realize fridges have digital control systems ????

 

The logical answer is also the conclusion I would draw from Gibbo's test - that energy efficiency is not as important as cost in a domestic fridge and is a far more important factor in a 12V unit.

 

Which goes back to my original comment - they are not more efficient simply because they use 12v DC - if they are more efficient it is because the people who convert them install a more efficient refrigeration system when them make the conversion.

 

It's a pity someone doesn't make an el-cheapo 12v conversion - I would gladly trade off high capital cost for lower efficiency.

[Ex- Member]

I think the way to look at fridge options today is the cost between 12 volt and 240 volt, we bought a good quality 240 volt fridge A+ rated this still came out £400.00 cheaper than a 12 volt quality fridge. The way I see it is £400.00 could buy today 200 watts of solar panels. If those were dedicated to a 240 volt fridge through an already installed inverter then even through the winter the panels would have a pretty good chance of supplying the power required. Of course through the summer you're gaining lots of additional energy for other things.

 

 

Someone also posted elsewhere yesterday the recorded power usage of a fridge over a year and as the ambient temperature drops during the winter so did the fridges power requirements to quite an extent.

[Robin2]

I think the way to look at fridge options today is the cost between 12 volt and 240 volt, we bought a good quality 240 volt fridge A+ rated this still came out £400.00 cheaper than a 12 volt quality fridge. The way I see it is £400.00 could buy today 200 watts of solar panels. If those were dedicated to a 240 volt fridge through an already installed inverter then even through the winter the panels would have a pretty good chance of supplying the power required. Of course through the summer you're gaining lots of additional energy for other things.

 

 

Someone also posted elsewhere yesterday the recorded power usage of a fridge over a year and as the ambient temperature drops during the winter so did the fridges power requirements to quite an extent.

 

This seems to make sense to me.

 

A 12v fridge makes no economic sense if you are on shore power most of the time. If you are not on shore power and generate all your electricity with diesel or petrol the 12v fridge might make sense if it offered a sufficient saving of expensive electricity. However once you have solar panels your average electricity cost falls and so does the justification for a 12v fridge.

[WotEver]

I didn't realize fridges have digital control systems ????

I never suggested they did. You were querying why AC motors were less efficient than DC and a quick Google threw that up.

 

Tony